Free Tool — Crane
Crane Load Ratio Calculator
Calculate load-to-capacity ratio from load weight, rigging weight, and crane rated capacity. Includes OSHA and ASME B30.5 reference values tested on the NCCCO exam.
Crane Load Ratio Calculator
From load chart at current radius
Slings, hooks, shackles, blocks
Jib, block, extra rope weight
Load-to-Capacity Ratio
38.8%
✓ Within safe operating range
Total Load
15,500 lbs
Net Capacity
40,000 lbs
Safety Margin
24,500 lbs
OSHA / ASME Reference
Load Ratio = (Load + Rigging) ÷ Net Capacity × 100
ASME B30.5: Do not exceed rated capacity under any conditions
75% threshold: Common industry practice for operational safety margin
Pro Insights
- Recommended lift radius for this load weight:See in app
- ASME B30.5 hand signal for this lift type:See in app
- Required inspection interval at this capacity:See in app
Crane Prep
Pass the NCCCO Crane Operator Exam
1,000+ practice questions + load chart calculator — works offline
NCCCO Exam: Load Chart Basics
The NCCCO Written Exam and Practical Exam both test load chart reading. A load chart shows the crane's rated capacity at various boom lengths and load radii (horizontal distance from the center of rotation to the load). As radius increases, rated capacity decreases.
Key concepts tested: reading capacity tables by boom angle and length, understanding deductions (the weight of the hook block, headache ball, slings, and shackles must be subtracted from rated capacity), and two-blocking prevention (the condition where the hook block contacts the sheave at the boom tip).
Rated capacity always assumes specific outrigger/crawler configurations, level ground, and standard boom. Operating on slopes, with a jib, or with reduced outrigger extension significantly reduces safe working loads and requires consulting derate tables.
Frequently Asked Questions
What load ratio does OSHA consider safe?
OSHA 1926.1417 requires cranes to operate within the manufacturer's rated capacity. Industry practice (and ASME B30.5) treats 75–90% as the working zone — most rigging plans target a load ratio below 85%. At 90% and above, a critical lift plan is typically required. Any load exceeding 100% of rated capacity is prohibited.
What deductions must be made from crane rated capacity?
Rated capacity is the load the crane can lift — but the crane is also lifting its own rigging. The weight of hook blocks, headache balls, slings, shackles, and spreader bars must all be subtracted from rated capacity before determining the maximum payload. This is a critical distinction on the NCCCO exam.
How does boom radius affect crane capacity?
As the load radius (horizontal distance from the center of rotation to the load) increases, crane rated capacity decreases significantly. Load charts provide capacity values at specific radius and boom length combinations. Always read the chart for the exact configuration — interpolation is allowed but extrapolation is not.
Does the NCCCO exam include load chart reading?
Yes — load chart reading and interpretation is one of the heaviest-weighted topics on the NCCCO Written Core Exam and is also evaluated in the Practical Exam. Candidates must be able to determine rated capacity at a given radius and boom length, apply deductions, and calculate load ratio. Practice with multiple crane manufacturer load charts before the exam.
Also try: OSHA Fall Clearance Calculator
Total fall clearance distance per OSHA 1926.502 — pass/fail by anchor height