What Is a Crane Boom Angle Calculator?
This calculator turns three simple field measurements — boom length, boom pivot height and the height you need the hook to reach — into the boom angle from horizontal and the resulting horizontal reach. It applies the same right-triangle geometry printed on manufacturer load-radius diagrams, so you can sanity-check a lift plan before you swing the boom into position.
It is a geometry tool, not a capacity tool. The angle and reach it produces still need to be checked against your crane's official rated capacity (load) chart for that boom length, angle and configuration before any lift.
How to Read Your Results
Boom Angle From Horizontal
This is the angle the boom makes with a flat, level line — the same angle indicator most cranes show in the cab. A higher angle means a steeper, shorter-reach boom position; a lower angle means a flatter, longer-reach position.
Horizontal Reach
The horizontal distance from the boom's pivot point to the point directly below the hook. This is the geometric component of load radius — actual load radius also depends on where the pivot sits relative to the crane's center of rotation.
Vertical Rise Needed
The difference between your target hook height and the boom pivot height — the vertical leg of the triangle the calculator solves.
Angle From Vertical
The complement of the boom angle (90° − boom angle), shown because some cranes and load charts reference angle from vertical instead of from horizontal.
Real-World Example
A mobile crane has a 100ft boom pivoting from a 10ft-high turntable. The job needs the hook 80ft above the ground.
| Measurement | Value |
|---|---|
| Boom length | 100 ft |
| Pivot height | 10 ft |
| Vertical rise needed | 70 ft |
| Boom angle | ≈44.4° |
| Horizontal reach | ≈71.4 ft |
With 70ft of the 100ft boom used for vertical rise, trigonometry places the boom at roughly 44.4° from horizontal, leaving about 71.4ft of horizontal reach for the load radius.
Tips for Boom Angle Planning
- Longer boom, same height means a shallower angle and more horizontal reach.
- Steeper angles reduce reach but generally allow higher rated capacities at a given radius.
- Always verify against the load chart — this calculator does not know your crane's rated capacity at any given radius.
- Account for boom deflection under load; a loaded boom sags slightly, changing the real angle and reach.
Related Calculators
Last updated: August 2026 · Reviewed by: Simple Calculator Tools Editorial Team