How to Read a Crane Load Chart: A Worked Boom-Truck Example

By Michael StormantMay 24, 2026Updated Oct 9, 202624 min read

Here is how to read a crane load chart: confirm the chart page matches the machine’s exact configuration, measure the load radius and round up to the next printed row, read across to the boom length you’ll carry (taking the smaller capacity between columns), then subtract every deduction the notes require. What’s left is net capacity, and the verified load weight has to fit under it. The number printed in the chart cell is never the number you can put on the hook. Below is the 10-step routine, then one realistic boom-truck pick worked through an illustrative chart and range diagram until the gross-versus-net trap can’t catch you.

How to Read a Crane Load Chart in 10 Steps

Order matters as much as content. Work it top to bottom, because every step below depends on the ones above it, and jumping around is how a flawless calculation ends up describing a machine that isn’t there.

1. Verify the load weight from a document, and add anything attached to it.
2. Set up and level the machine, and lock in the outrigger configuration you’ll use for the whole lift.
3. Pull the chart page matching that configuration, counterweight, and work area.
4. Measure the radius, then round up to the next printed row, allowing for deflection and boom-down.
5. Find the boom length column you’ll carry, confirmed on the range diagram, and take the smaller capacity between columns.
6. Read the gross capacity and write it down.
7. Subtract every deduction the notes require — block or downhaul weight, jib, rigging, below-the-hook devices.
8. Check parts of line against permissible line pull.
9. Compare net capacity to the verified weight, and calculate the percentage of chart used.
10. If that percentage triggers a written lift plan, write one before the hook moves.

Download the 10-Step Load Chart Card (PDF)

The card puts these ten steps, the round-against-yourself rules, and a fill-in pick worksheet on one sheet. Ten steps, five minutes, and the difference between running a crane and planning a lift. Employers who want that habit verified rather than assumed build it into the on-machine operator evaluation, where the candidate works a real chart against a real setup instead of reciting rules.

Why the Load Chart Outranks Everyone on Site

Every crane carries one document that outranks the operator, the foreman, and the superintendent: the load chart. It states exactly what the machine will lift at a given radius, at a given boom length, in one specific configuration — and not a pound more. Learning to read it isn’t exam trivia. It’s the line between a clean pick and a crane on its side.

OSHA treats that document as equipment, not paperwork. Under 29 CFR 1926.1417, the load charts, operating procedures, and operator’s manual have to be readily available in the cab at all times, the equipment can’t be operated past its rated capacity, and the operator has to verify the load is within rated capacity — from a recognized weight source, or by checking it on a load indicator as the lift begins. A laminated page in the door pocket nobody has opened since delivery satisfies nothing. The rest of the operating rules live in 29 CFR 1926 Subpart CC, and nearly all of them assume chart literacy as a starting point.

The fastest way to get a crane capacity chart explained is to quit talking theory and work a pick, so that’s what we’ll do here — one boom-truck lift, start to finish, the same way we run it in our load chart training. The numbers below are generic teaching numbers on an illustrative chart, because every manufacturer publishes its own charts and they are never interchangeable. The method works on any telescopic crane you’ll ever climb into.

What’s Actually in the Book

Operators say “the load chart” like it’s one page. It’s a book, and the capacity grid is only part of it:

• The range diagram. A scale drawing of boom lengths, angles, radii, and tip heights. This is where you answer “will 70 feet of boom clear that parapet at 42 feet,” before you open the capacity grid at all.
• The working area diagram. A plan view of the over-rear, over-side, and over-front zones drawn against the outrigger footprint. Many boom trucks publish little or no capacity over the front, and OSHA bars lifting over the front of wheel-mounted equipment unless the manufacturer permits it.
• Capacity charts, one per configuration. Fully extended outriggers, intermediate, retracted, on rubber stationary, pick-and-carry. Separate pages. They do not blend.
• The notes. Deductions, minimum parts of line, boom-angle limits, wind statements, whether capacity is governed by structure or stability. Binding, not commentary.
• Wire rope and reeving data. Permissible line pull per part and maximum parts of line — the limit that quietly caps a lot of picks.
• Attachment charts. A jib gets its own page, and erecting or even stowing it changes the main boom numbers.

Skip any one of those and you’re reading a fragment. The grid alone will happily hand you a number the notes forbid you to use.

The Pick: One Air Handler, One Boom Truck

Here’s the job. A mechanical contractor needs a rooftop air handler set on a single-story building. The data plate says the unit weighs 5,800 pounds — verified weight, not a guess shouted up from the ground. Site conditions force the crane to set up where the hook will land 42 feet from the centerline of rotation, and clearing the parapet at that distance takes roughly 70 feet of boom.

The machine is a typical telescopic boom truck — the fixed-cab configuration that tests under NCCCO’s TSS designation, while its swing-cab cousins fall under TLL. Both live in the mobile crane certification family. Setup for this boom truck load chart example: outriggers fully extended, tires clear of the ground, no jib erected, single part of line. Write every one of those details down, because they decide which page of the chart we’re even allowed to read.

Weight first, always. A data plate, shipping ticket, mill cert, or scale ticket is a verified weight. A number somebody remembers from the last one is not. If the load is an odd assembly with no documentation, that problem belongs to a qualified rigger before it belongs to the operator, and the answer is usually a scale rather than arithmetic on a tailgate. OSHA backs that up: if the operator relies on a load indicator instead of a documented weight and the reading comes in over 75 percent of the maximum rated capacity at the longest radius of the lift, the lift stops until the weight is verified from a recognized source (29 CFR 1926.1417(o)(3)).

Geometry comes before capacity. Every boom length below can reach 42 feet; the range diagram shows which ones leave room to carry the unit over the parapet.

Step One: Match the Chart Page to the Machine

A number read off the wrong page is not a smaller mistake than bad arithmetic. It is usually a bigger one, because the arithmetic will check out perfectly. Before you touch a figure, confirm three things about the machine as it sits right now:

• Outrigger position. Fully extended, intermediate, and retracted each get their own chart, and the on-rubber chart is a different world. Half-extended outriggers do not get half the capacity — they get their own published column, and if the manufacturer never published one for that position, that position isn’t authorized.
• Work area. Plenty of boom trucks rate higher over the rear than over the side. Know every quadrant the boom will swing through during the pick, not just where it starts. If the load leaves the truck over the rear and lands over the side, the side number governs the whole lift.
• Counterweight and attachments. If the chart was built around a specific counterweight package, or assumes the jib is stowed a certain way, the notes say so. OSHA won’t let the machine run without the counterweight the manufacturer specifies, or with more than its maximum (29 CFR 1926.1417(aa)).

Operators get in trouble by grabbing the biggest number on the page and assuming it travels with the crane. It doesn’t. Change the configuration and you’ve changed the chart.

Here is the page for our setup — an illustrative teaching chart built for this example, not copied from any manufacturer:

Step Two: Nail the Radius and Round Up

Load radius is the horizontal distance from the centerline of rotation to the center of the hook. Not from the cab, not from the outrigger pad, not from the bumper. Measure it — our hook lands at 42 feet.

Most charts won’t print a 42-foot row. Ours jumps from 40 feet to 45 feet, and the rule is absolute: when the radius falls between rows, use the larger radius. Never interpolate and never split the difference, because capacity doesn’t drop in a straight line. We read the 45-foot row.

One more wrinkle: charts are built on loaded radius. The boom deflects when the load comes off the ground, and deflection pushes the hook farther out. Our 42 feet might become 43 or 44 under load — still inside the 45-foot row we chose. But a pick taped at 44 feet on an empty hook can flex past 45 once it’s loaded, and now you’re operating on a row you never read. Radius also grows when you boom down, when you swing across an out-of-level machine, and when you have to reach past scaffold you forgot about. Plan for the worst radius the load will ever occupy.

Step Three: Cross Radius Against Boom Length

Now find the column for the boom you’re actually carrying. With 70 feet of boom out and the 45-foot radius row, our chart reads 6,750 pounds. That’s the gross capacity — the most this machine will support in this exact configuration, period.

Two traps live in this step. If your boom length lands between columns, take the column that gives the smaller capacity, just like you rounded the radius. And longer boom is never free: scope this same crane to its 80-foot column at the same 45-foot radius and the cell drops to 6,100 pounds. Telescoping out doesn’t just reach farther — it costs capacity at every radius. Carry the boom the pick requires and nothing extra.

Some charts index by boom angle instead of boom length, lattice charts especially. The logic flips in a way that catches people: a lower angle means a longer radius, so between published angles you take the lower one. The principle never changes. Round toward the smaller capacity, on every variable.

Step Four: Deduct Everything That Isn’t the Load

Here’s the trap that bites hardest. The 6,750 in the cell is not what you can hang on the hook. The crane supports everything below the boom head, and the chart expects you to subtract whatever isn’t load. Our chart’s notes call out three deductions for this setup:

• Stowed jib carried on the base section: 350 pounds
• Downhaul weight and hook: 140 pounds
• Slings and shackles for this rigging arrangement: 85 pounds

That’s 575 pounds of deductions. Net capacity: 6,750 minus 575 = 6,175 pounds. Against a 5,800-pound air handler, the pick is good — with 375 pounds of margin, sitting around 94 percent of net. That’s a legal lift. It is also exactly the kind of pick a smart lift director puts on paper, because many contractor lift programs set a percentage-of-chart threshold above which a written plan is required, and a pick sitting this close to net capacity lands above nearly any threshold a program uses. OSHA’s steel erection rule calls a lift over 75 percent of rated capacity a critical lift (29 CFR 1926.751). On federal work that invokes EM 385-1-1, the edition your contract cites adds its own planning rules on top of OSHA: in the 2024 edition, a lift over 75 percent of the load chart during construction work is a critical lift that needs a written Critical Lift Plan, prepared by a competent or qualified person and submitted to the USACE supervisor for approval or to the contracting officer or COR for acceptance (paragraphs 16-2.j and 16-7.d). Our EM 385-1-1 crane training works that plan format specifically.

Some charts list slings and rigging as deductions, the way this one does; others tell you to add them to the load weight instead. The margin comes out the same either way — just count them once, never zero times and never twice.

Creative rigging is where margin quietly disappears. Swap two nylon slings for a spreader beam and you may have added several hundred pounds without touching the load. Any below-the-hook lifting device counts at its full marked weight. So does a tag line block, a second hook, or a headache ball you left reeved. Weigh the rigging arrangement once and write it on a card in the box; guessing every morning is how 85 pounds becomes 300.

The Same Pick, Two Boom Lengths

Now run the careless version. The operator sees 6,750, knows the unit weighs 5,800, and figures they have nearly a thousand pounds of room. They never had it — 375 was the real number. And if they scope out to 80 feet because it feels easier to clear the parapet, the pick collapses. Same crane, same radius, same load:

Ten feet of boom apart, and one of them is an incident report. The chart knew before the crane did.

Round Against Yourself, Every Time

Examiners hammer this because the field gets it backwards. Every variable in a chart problem has a direction that flatters the crane and a direction that protects it, and you go the protective way on all of them.

This is not caution for its own sake. The published values are the only points the manufacturer actually validated. Everything in between them is your assumption, and an assumption belongs on the safe side of the number.

Parts of Line: The Limit Nobody Reads

The capacity grid assumes the hoist rope can carry whatever the structure can. Sometimes it can’t. Every chart publishes a permissible line pull per part, and the governing capacity is that line pull times the number of parts actually reeved.

Our pick runs single part, so the rope carries the full 5,800 pounds plus everything under it — 85 pounds of slings and the 140-pound downhaul weight and hook, 6,025 pounds in all. Our chart allows 7,500 pounds of line pull per part, so one part works with about 80 percent of the line pull in use. If the single-part line pull were below the hook load, the 6,750 in the cell would be irrelevant — you’d reeve a second part, then go back and redo the deductions, because two-part reeving usually means a heavier block. More parts, more rope capacity, less capacity in the cell. And when a load reaches 90 percent or more of the maximum line pull, OSHA has the operator test the brakes by lifting it a few inches and applying them (29 CFR 1926.1417(s)). Rope condition is not a chart variable, either: broken wires or a crushed section don’t earn a derated chart, they earn a replacement. Same discipline that governs slings and hardware, and the same reason sling angle math belongs next to chart math in every rigger’s head.

Tipping, Structure, and Why the Difference Matters

Part of every mobile crane chart is limited by stability — the point where the machine would begin to tip — and part is limited by structural strength in the boom, turntable, or outrigger box. Most charts mark the transition with bold type, shading, or a footnote. On our illustrative chart, the shaded cells are the structural zone: with 70 feet of boom, the 40-foot row is strength-limited and the 45-foot row we’re reading is stability-limited.

Know which zone you’re in, because the failure modes are nothing alike. In the stability zone an overload announces itself: the machine gets light, the off-side outrigger floats, the operator feels it coming. In the structural zone there is no warning at all. The crane sits flat and solid while a boom section yields. Short radius, high angle, heavy load is usually structural territory; long radius over the side is usually stability territory.

Which is also why the rated capacity indicator is an aid, not an authority. Under 1926.1416 those operational aids have to work, and when one is out of service the standard requires alternative measures while it’s repaired. The alternative measure is chart work by hand. And 1926.1417(k) says outright that safety devices and operational aids are no substitute for the operator’s judgment.

The Chart Assumes a Perfect World

A load chart is an engineering document describing a machine set up the way the engineers assumed it would be. The field hands you something else most mornings. Every condition below is already baked into the printed numbers, and every one of them is yours to reproduce:

• Level. Every capacity in the book assumes the machine sits inside the manufacturer’s published level tolerance, and that tolerance is a fraction of a degree — considerably tighter than “the bubble looks close.” Check it after the outriggers take load, not before. Out-of-level costs the most at long radius over the side, where a small tilt walks the load a surprising distance farther out.
• Supporting ground. 29 CFR 1926.1402 puts ground conditions on the controlling entity, but the crane still sinks on the operator’s watch. Pads sized to the soil, cribbing where it’s soft, and a hard look for backfill, trenches, and basement walls.
• Freely suspended load. Charts assume the load hangs plumb. Dragging it sideways or breaking it free from a form generates side load the chart never contemplated.
• Still air. Manufacturers publish a wind limitation in the notes. A big flat air handler is a sail, and sail area matters more than weight once the wind picks up.
• Smooth control. Sudden stops and fast swings spike the actual load well above its static weight — a good reason the operator and signal person work off the same plan and the same crane hand signals chart instead of inventing motions.

The chart tells you what the crane can support. It says nothing about whether today lets you get there.

Charts That Don’t Look Like This One

The method transfers; the format doesn’t always.

• Lattice boom cranes. Usually indexed by boom length and angle rather than radius, with separate pages for boom-and-jib combinations. Operators moving into lattice boom crawler crane work spend most of their study time on angle-indexed reading.
• Articulating and knuckle-boom cranes. Capacity is published per boom section and extension, and the numbers change hard as each knuckle unfolds. If you run a loader crane, articulating crane certification covers a layout that looks nothing like a telescopic grid.
• Service truck cranes. Small charts, big trouble. The crane on the back of a service body still has a radius and a stability limit, and service truck crane operators often work alone with nobody to catch a mistake.
• Rough-terrain machines. Same telescopic logic, more outrigger configurations, and on-rubber charts that actually get used. Crews sizing up both usually start with boom truck versus rough terrain.

Where Good Operators Get Burned

The chart-reading mistakes that bend iron are rarely exotic. They’re Tuesday-afternoon shortcuts:

• Reading the wrong page. On-outrigger numbers while sitting on rubber, or the over-rear chart while the pick swings over the side.
• Trusting yesterday’s lift. “She picked it fine last week” means last week’s radius and last week’s configuration.
• Planning half the lift. The radius where the load leaves the truck and the radius where it sets are rarely the same number, and the chart governs on the larger one. Walk the whole arc before you pick, not just the part you can see from the seat.
• Skipping the notes. Deductions, parts-of-line minimums, areas of operation — the fine print is load-bearing.
• Treating the load moment indicator as the plan. It confirms the plan you already made. When it disagrees with your arithmetic, stop: one of the two is wrong and you don’t yet know which.
• Guessing the load. A clean calculation built on a made-up weight is still a made-up answer.

Every item on that list is preventable with the same five-minute routine at the top of this page. Run it on every pick, even the easy ones. Especially the easy ones.

Make Chart Work a Reflex Before Test Day

Load chart problems are a core part of the NCCCO mobile crane written exams, and they look a lot like the pick we just planned. If you’re testing soon, drill timed problems with our NCCCO practice test until the round-up rules and deduction math run on autopilot, then check what else the written exam covers so charts aren’t the only thing you studied. The credential matters because 29 CFR 1926.1427 requires operators to be certified for the equipment they run, and NCCCO certification is what we train crews to earn — valid for five years before recertification.

If the boom truck in this example is the machine you run, our boom truck certification program builds chart work like this into both the classroom and the practical. We’ve trained crews from more than 1,000 companies — at our Goldsboro, NC training center at 309 N William St, where you can run the NCCCO demo exam before test day; at our hands-on partner yard at Harris Steel Erectors; or employer-based at your site, anywhere in the country and OCONUS. Call (252) 274-0583 or tell us about your crew and we’ll build the class around the charts your operators actually use.

Frequently Asked Questions

What’s the best way to find the load capacity of a crane?

Read it out of the manufacturer’s load chart for that crane’s exact configuration — there is no other valid source. Find the page matching your outrigger position, counterweight, and work area, find the row for your loaded radius, read across to your boom length column, then subtract the hook block, rigging, and attachments the notes require. The capacity stamped on the data plate is the maximum at the shortest radius and tells you almost nothing about the pick in front of you. A load test checks the machine against its chart; it never raises the chart.

What’s the difference between gross and net capacity on a crane load chart?

Gross capacity is the number printed in the chart cell for your exact configuration, boom length, and radius. Net capacity is what’s left after you subtract everything hanging below the boom head that isn’t the load — hook block or downhaul weight, slings and shackles, and a stowed or erected jib when the notes require it. Your load can never exceed net. Operators get hurt comparing the load to the gross number and lifting on margin they don’t have.

How do you read a load chart for a crane, step by step?

Configuration, radius, boom length, gross number, deductions, net against verified weight — in that order. Confirm the setup and pull the matching page first, because every other number depends on it. Measure radius from the centerline of rotation to the center of the hook and round up to the next printed row. Cross that row against the boom length you’ll carry, take the gross figure, subtract the required deductions, and compare to a documented weight. Reverse the order and you’ll eventually read a correct number off the wrong page.

What do I do when my radius falls between two rows on the chart?

Round against yourself, always. Use the next larger radius row, and if boom length falls between columns, use whichever column gives the smaller capacity. Never interpolate — capacity doesn’t change in a straight line between chart values, so splitting the difference invents a number the manufacturer never published. Plan on the loaded radius too, because deflection pushes the hook farther out once the load comes off the ground.

Does the load chart already include the hook block and rigging?

Generally no. Most charts publish gross capacity and require you to deduct the hook block or downhaul weight, rigging hardware, and attachments like a stowed jib before comparing anything to the load. The notes spell out exactly what must be deducted for your configuration, which is why reading them comes first. Some charts and exam manuals have you add slings and rigging to the load weight instead of deducting them; the margin comes out the same as long as you count them once. When in doubt, treat everything below the boom head that isn’t crane structure as a deduction.

Where do I find the load chart for my boom truck?

In the cab, and it has to be there. 29 CFR 1926.1417 requires the rated capacities, operating procedures, and the operator’s manual to be readily available in the cab at all times. If the capacities live only in an electronic display and it fails, operations stop until they’re available again. If the chart book is missing, damaged, or belongs to a different serial number or counterweight package, the machine gets parked until the right one is aboard. Manufacturers will supply a replacement for the specific serial number; a chart downloaded for a similar model is not a substitute.

Do the numbers change if I use short or intermediate outriggers?

Yes, and not proportionally. Retracted and intermediate positions have their own published charts, and the drop from fully extended is steep, particularly over the side. If the manufacturer never published a chart for the position you’re sitting in, that position is not an approved configuration and there is no number to read. Same logic on rubber: stationary-on-tires and pick-and-carry are separate charts with their own boom, radius, and travel restrictions.

Are load chart problems on the NCCCO written exam?

Yes. Load chart reading is a core part of the NCCCO mobile crane written exams, and the problems work just like the example above: pick the right page, round the radius, find the boom length, apply deductions, and compare net capacity to the load. Timed practice is the best preparation, and the skill carries straight from the test center to the seat. NCCCO certifications are valid for five years before recertification.

Authoritative References

• OSHA 29 CFR 1926.1417 — operation: load charts in the cab, rated capacity, load weight verification, and line pull brake tests.
• OSHA 1926.1427 operator certification — the federal rule text, straight from OSHA.
• OSHA 29 CFR 1926.751 — steel erection definitions, including “critical lift.”
• ASME B30.5 Mobile and Locomotive Cranes — the consensus standard for mobile crane construction, inspection, and operation (current edition 2025).
• USACE EM 385-1-1 (2024) — the federal safety manual and its critical lift criteria; use the edition your contract cites.
• NCCCO — the certifying body, with exam details and candidate policies.

Bring us the chart book your crew actually uses. Call (252) 274-0583 or request a quote — we’ll build mobile crane certification training around the charts in your own cabs, coffee rings and all, on your jobsite nationwide and OCONUS, or at our Goldsboro, NC crane operator school.