Crane Size & Capacity Estimator
Calculate the required crane capacity and boom length based on load and distance.
Total Gross Weight:
Minimum Boom Length Required:
Minimum Crane Rated Capacity:
*Disclaimer: This is an estimation. Always consult a certified lift director and official load charts before any lift.
How to Calculate Crane Size for Your Project
Choosing the right crane is critical for both safety and cost-efficiency. Using an undersized crane leads to structural failure or tipping, while an oversized crane results in unnecessary mobilization costs. To accurately size a crane, you must understand the relationship between weight, distance (radius), and the crane's center of gravity.
Key Factors in Crane Sizing
- Gross Load: This is the total weight the crane must support. It includes the net load weight PLUS the weight of the hook block, overhaul ball, and all rigging hardware (slings, spreaders, shackles).
- Operating Radius: This is the horizontal distance from the center of the crane's rotation to the center of gravity of the load. As the radius increases, the crane's lifting capacity decreases significantly.
- Boom Length: Determined by the height of the lift and the radius. Using the Pythagorean theorem, we estimate the straight-line distance from the boom tip to the crane base.
- The 75% Rule: Most professional operators never exceed 75% to 85% of a crane's rated capacity for a specific configuration to account for wind, dynamic loading, and ground stability.
Example Calculation
Imagine you need to lift a 15-ton HVAC unit onto a roof. The unit is 40 feet away from where the crane can safely park, and the roof is 30 feet high. You are using 1 ton of rigging gear.
- Total Weight: 15 (Load) + 1 (Rigging) = 16 Tons.
- Boom Length: √ (40² + 30²) = 50 Feet.
- Capacity Calculation: If you apply a 75% safety margin, you need a crane that is rated for at least 21.3 Tons at a 40-foot radius.
Critical Safety Note
Ground conditions, wind speeds, and boom angle significantly impact real-world capacity. This calculator provides a mathematical baseline, but a formal Lift Plan should always be performed by a qualified professional using the specific manufacturer's load charts for the exact crane model being used.