A load chart isn't complicated once you know what you're looking at. Here's the version nobody hands you until you've already missed a practice question on it.
What a load chart actually tells you
A load chart is the manufacturer's answer to one question: how much can this crane lift, safely, in this exact setup? It's not one number — it changes with boom length, radius, angle, and how the crane is configured. Change any one of those, and the number you're allowed to lift changes with it.
Every chart is built around four variables:
Radius — the horizontal distance from the crane's center of rotation to the center of the load. Not the boom length. Not the distance to the tip. The load itself.
Boom length — how far the boom is extended, measured in feet.
Boom angle — the angle between the boom and horizontal. Charts sometimes list this instead of (or alongside) radius, since the two are related.
Configuration — outriggers fully extended vs. partially extended, counterweight installed vs. removed, on rubber vs. on outriggers. Each configuration gets its own chart or its own column, because each one changes what the crane can safely handle.
Get any one of these wrong when you read the chart, and you're not reading the chart — you're guessing.
The relationship that trips people up
As radius increases, capacity decreases. That's the one fact every chart is built around, and it's also the fact most missed on practice exams. A longer radius means more leverage working against the crane's tipping point, so the rated capacity drops even though nothing about the load itself changed.
Boom length works against you the same way at a given radius: a longer boom generally means less capacity at that radius, because more of the boom's own weight is now working against the crane.
Example chart (for practice only)
This is a simplified, illustrative chart — not a real manufacturer's rating. Never use a made-up chart like this on an actual job. It exists here so you can practice pulling numbers the way you would on exam day.
| Radius (ft) | Boom Length 40 ft | Boom Length 60 ft | Boom Length 80 ft |
|---|---|---|---|
| 10 | 44,000 lb | 38,500 lb | — |
| 15 | 29,000 lb | 26,000 lb | 22,500 lb |
| 20 | 19,500 lb | 18,000 lb | 16,000 lb |
| 30 | — | 10,500 lb | 9,800 lb |
| 40 | — | 6,200 lb | 6,000 lb |
| 50 | — | — | 3,900 lb |
A dash means that combination isn't rated — the boom can't reach that radius at that length, or the manufacturer simply doesn't certify it there. If it's not on the chart, it's not a lift you make.
Reading it: find your radius down the left column, find your boom length across the top, and read the number where they meet. That number is your rated capacity for that exact setup — full stop, before you've subtracted anything else.
Now subtract your deductions
The number in the chart is the crane's rated gross capacity — not what's left over for your actual load. Before you rig anything, you subtract the weight of everything hanging below the hook that isn't the payload:
- Headache ball or hook block
- Slings, shackles, and other rigging
- Any spreader bar or below-the-hook lifting device
Whatever's left after those deductions is your true net capacity — the maximum your payload can actually weigh.
Know your quadrant
Capacity isn't always the same all the way around the crane. Many charts break capacity into working quadrants — over the front, over the side, and over the rear — because outrigger loading and stability change depending on which direction the boom is pointing. A chart may rate a heavier lift over the rear than over the side on the exact same crane. Always confirm which quadrant's numbers you're reading before you trust them.
Exam tips
Load chart questions make up a real chunk of both the core and specialty written exams, and they're some of the most missable points on the test if you haven't drilled them:
- Always identify the configuration first — outriggers vs. on rubber, counterweight in or out. Reading the wrong column is the single most common mistake.
- Round toward the conservative number when a value falls between two listed radii — charts don't interpolate for you on the exam, so know whether the question wants the next radius up or expects you to reason about it.
- Don't forget deductions — a question that gives you a gross capacity and asks for net capacity is testing whether you remember to subtract rigging weight, not just whether you can read a table.
- Watch the units — most U.S. charts are in pounds, but don't assume; the question or chart header will tell you.
- Practice until it's fast — on exam day you won't have time to relearn the layout of a chart. Familiarity is what saves you the minute.
This walkthrough covers the fundamentals. The full load chart practice sets — real exam-style scenarios across radius, boom length, and configuration changes — are built into the Core Exam Practice Bank and every specialty guide.