Jib Crane Design Calculator
Jib crane boom and foundation sizing from capacity.
About this calculator
This calculator sizes the three structural pieces of a jib crane — boom, mast, and foundation — from nothing more than the rated capacity and a few geometric inputs, using simplified beam and column formulas rather than a full engineered design. The boom is treated as a simple cantilevered beam: bending moment is capacity times span times 12 (converting the span in feet to inches), and dividing that by an assumed 20,000 psi allowable bending stress for structural steel gives the required section modulus (Sx) — the number you'd match against a wide-flange beam table when picking an actual boom section. Mast pipe outside diameter is selected from a tiered lookup driven by an inflated column load (capacity times 1.5, a rough allowance for dynamic loading from swinging and dead weight beyond the static rated load), stepping through standard 6–12 in pipe sizes as that load grows.
Foundation diameter is a simple rule of thumb — twice the mast pipe diameter plus 12 in — and foundation depth scales loosely with under-boom height, with a 4 ft floor. Coverage area treats the boom span as a sweep radius and computes the pie-slice area of your entered rotation arc (90–360°) using the circle-area formula scaled by the fraction of a full circle the arc represents. None of these figures substitute for a stamped structural engineering design — local soil conditions, wind loading, and duty cycle can all move the real foundation and beam requirements well beyond this estimate — but they're a solid starting point for scoping a jib crane before involving an engineer.
Inputs
Results
Boom Sx (in^3)
18
How to Use This Calculator
- Enter the required lifting capacity (lb) for the heaviest load the crane will handle.
- Set the boom span (ft) — the horizontal reach from the mast centerline to the hook.
- Enter the under-boom height (ft) — clearance available beneath the boom arm.
- Input the rotation arc (degrees) — how far the boom swings (90° to 360°).
- Use Boom Sx (in³) to select a structural beam section, and Foundation dia (in) and Foundation depth (ft) for anchor design.
How the result changes with Capacity (lb)
| Capacity (lb) | Boom Sx (in^3) |
|---|---|
| 1,000 | 9 |
| 1,500 | 13.5 |
| 3,000 | 27 |
| 5,000 | 45 |
What each input means
- Capacity (lb)
- Required lifting capacity.
- Boom span (ft)
- Boom arm length (reach) in feet.
- Under-boom height (ft)
- Height under the boom in feet.
- Rotation (degrees)
- Boom rotation arc in degrees.
What each result means
- Boom Sx (in^3)
- Required section modulus for the boom beam.
- Mast pipe OD (in)
- Recommended mast pipe outside diameter.
- Foundation dia (in)
- Recommended foundation pier diameter.
- Foundation depth (ft)
- Recommended foundation pier depth.
- Coverage (sq ft)
- Working area covered by the jib crane.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersCapacity (lb) = 2000, Boom span (ft) = 15, Under-boom height (ft) = 12, Rotation (degrees) = 200 = 4 input(s) provided
- Calculate Boom SxBoom Sx = round(moment / 20000 * 100) / 10018 = 18
- Calculate Mast pipe OD8 = 8
- Calculate Foundation diaFoundation dia = mastPipeOD * 2 + 1228 = 28
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does doubling the boom span more than double the required section modulus?
Bending moment is capacity times span times 12, so span enters the moment linearly — doubling span alone does exactly double the moment and therefore the required Sx. It only feels like more than doubling because a longer boom is also often paired with a higher capacity requirement in practice; taken in isolation, this calculator's moment and Sx scale directly with span, one-to-one.
Why does the mast pipe size jump in fixed steps instead of scaling smoothly with capacity?
Mast pipe OD comes from a tiered lookup on column load (capacity times 1.5): under 3,000 lb picks 6 in, under 6,000 lb picks 8 in, under 12,000 lb picks 10 in, and anything higher picks 12 in. This mirrors how mast pipe is actually purchased — in a handful of standard commercial diameters — so the output jumps between those fixed sizes rather than reporting a continuous, non-buildable value.
Why is the column load used for mast sizing 50% higher than the rated capacity I entered?
The calculator multiplies capacity by 1.5 to get column load specifically for mast pipe selection, as a rough allowance for dynamic effects from the boom swinging plus the boom and trolley's own dead weight riding on top of the static rated load. Sizing the mast only to the static rated capacity would ignore those real added loads, so the 1.5 factor is a deliberate safety margin baked into that one calculation.
Why does increasing the rotation input change the coverage area but not the boom or mast sizing?
Rotation only feeds into the coverage-area formula — the pie-slice area of a circle with the boom span as its radius, scaled by rotation divided by 360 — and never appears in the moment, section modulus, or mast pipe calculations. Physically, how far the boom sweeps around doesn't change the load it has to carry at any given position, so the structural sizing depends only on span and capacity, not on the total arc of travel.
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