Crane Load Chart and Capacity Guide for Project Managers

A crane's headline capacity, such as 100 tonnes, is the most it can lift under the best conditions: close to the crane, on a short boom, on firm ground with outriggers fully extended. Real lifts rarely look like that. The load chart shows what the crane can do under the actual set-up. Reading it correctly is the single most useful skill when you rent a crane in Saudi Arabia, because it tells you whether the crane in the quote can do your lift.

How the chart works

Load charts pair boom length on one axis with lifting radius on the other. The point where the lines meet shows the maximum load for that set-up. The chart shows the safe limit under ideal conditions. It is not a target. Many modern cranes also have electronic load charts linked to the crane controls, which show live capacity based on current boom position and configuration.

Why radius changes everything

Capacity falls sharply as radius grows because of the lever effect. A 100 tonne crane rated at 10 metres may lift only 20 tonnes at 30 metres. Longer booms add reach but reduce lifting power, and higher boom angles generally allow heavier loads at shorter radii. Always give your rental company both the pick radius and the set-down radius, because the set-down point is often farther.

Typical capacity ranges

What reduces capacity on the day

• Outriggers and ground. Fully extended outriggers let a mobile crane reach rated capacity. Working on rubber instead of outriggers can cut capacity by 50 percent or more. Soft, uneven or sloped ground reduces safe capacity, which matters on sabkha and loose desert sand.
• Rigging weight. Hooks, slings, shackles and spreader beams count as load. On heavy lifts they can add tens of tonnes.
• Sling angle. At 15 degrees from horizontal, sling force can be more than 190 percent higher than a vertical lift.
• Wind. Work on standard gear often stops at about 20 to 25 mph (32 to 40 km/h). Large flat loads catch wind and swing.
• Height and clearance. Add margin for hook clearance and the gap below the load. One selection tool adds 3 metres for hook and rigging and 1 metre from ground to the bottom of the load.

A worked example

A contractor needs to set a 18 tonne pipe module at 22 metres radius, with 2 tonnes of rigging and a 3 metre hook allowance. The total load is 20 tonnes. The crane is acceptable only if its chart, for the boom length and counterweight planned, shows at least 20 tonnes at 22 metres with margin for wind and dynamic effects. A 50 tonne crane may fail this check at that radius, while a larger class passes. This is why the radius, not the module weight alone, drives the crane size and the quote. The numbers in this example are illustrative, not a lift plan.

Five questions to ask when a quote arrives

• Which crane model and boom length are you proposing for my radius?
• What is the rated capacity on the chart at that radius, and how much margin does it leave?
• What counterweight and outrigger configuration does that chart assume?
• Is rigging weight included in the figures, and who supplies the rigging?
• Can you send the chart and the inspection certificate before mobilisation?

Related services and guides

• Mobile and rough-terrain crane rental
• Rental showroom: crane classes
• Safety and compliance documents
• Equipment rental in Dammam
• How to choose a crane for rent

Sources: MYCRANE, load capacities and crane selection