What Is a Load Chart and How Do You Read One?

A crane load chart is the manufacturer’s table of maximum safe lifting capacities for a specific crane model, organized by lifting radius and boom configuration. To read one correctly, you find the row matching your planned radius, confirm the outrigger and counterweight configuration that applies, then read across to the capacity column that matches your boom length or angle. That number, not a rule of thumb, is the legal and safe lifting limit for that exact setup.

Every mobile crane ships with its own chart, and no two charts are interchangeable, even between cranes of the same rated tonnage. Reading one accurately is a core skill for lift planners, riggers, and crane operators in the UAE, where site conditions and load weights vary constantly across construction, oil and gas, and infrastructure projects.

Mobile Crane vs Crawler Crane

Key Takeaways
– A load chart lists maximum capacity by radius, boom length or angle, and outrigger/counterweight configuration, never as a single flat tonnage figure.
– The same crane can have multiple charts, one for each outrigger spread, and using the wrong column overstates capacity.
– Rigging gear weight (slings, shackles, spreader bars, hook block) must be subtracted from the chart capacity, not added on top of the load weight.
– Wind speed, load dynamics, and ground conditions can require derating below the printed chart number, so the chart is a starting point, not the final word.

What a Load Chart Actually Shows

A load chart is a table published by the crane manufacturer that states, for a given crane configuration, the maximum weight the crane can lift without exceeding its structural or stability limits. It is not a general guideline. It reflects load testing specific to that crane’s boom, outriggers, counterweights, and chassis.

The chart exists because a crane’s lifting capacity is not fixed. It changes constantly depending on how far the load sits from the crane’s center of rotation and how the boom is configured to reach it. A crane rated at a certain maximum tonnage can only lift that full weight under one narrow set of conditions, typically at minimum radius with the boom fully retracted or at its lowest angle. As radius or boom length increases, capacity drops, sometimes sharply.

Every operator and lift planner references the chart before every lift, not from memory, but from the physical document or its digital equivalent in the crane’s rated capacity indicator (RCI) system.

The Three Key Axes: Radius, Boom, and Capacity

Radius

Radius is the horizontal distance from the crane’s center of rotation (the centerline of the crane’s rotating superstructure) to the center of the suspended load. It is measured in meters, not from the crane’s edge or outrigger pads. As radius increases, the load creates more leverage against the crane’s tipping axis, which reduces how much weight can be safely lifted.

Lift planners calculate radius during site layout, factoring in where the crane can physically be positioned relative to the pick point and the set point. A shift of even one or two meters in crane position can move the load into a different row on the chart.

Boom Length and Angle

Boom length (for telescopic cranes) or boom configuration (for lattice-boom crawler cranes) is the second axis. Longer booms reach greater heights and radii but reduce capacity because the extended structure introduces more bending stress. Boom angle, the angle between the boom and horizontal, also affects both the achievable radius and the load path.

Load charts typically present boom length as separate chart pages or column groups, each with its own radius and capacity breakdown. Selecting the correct boom length section is the first filter before reading capacity values.

boom length explained

Capacity

Capacity is the maximum load weight, usually listed in metric tons for UAE-based fleets, that the crane can lift at the intersecting radius and boom configuration. This is the number lift planners cross-reference against the actual load weight plus rigging.

Capacity figures on the chart already account for the crane’s own structural limits and, on many charts, stability limits assuming ideal ground conditions. They do not automatically account for wind, dynamic loading, or non-level ground unless a separate note or deduction table says so.

How Outrigger Configuration and Counterweight Change the Chart

Most mobile cranes publish multiple load charts for the same machine because outrigger spread and counterweight directly change the crane’s stability footprint. A crane set up on fully extended outriggers has a wider base and higher capacity than the same crane on partially extended or retracted outriggers.

Counterweight works the same way. Adding counterweight shifts the crane’s center of gravity and increases capacity at longer radii, but it also increases the crane’s overall weight and ground bearing pressure, which matters for site inspections and mat or pad selection.

Reading the wrong chart section, one built for full outrigger extension when the actual site only allows partial extension, is one of the most consequential errors in crane operations. The crane’s rated capacity indicator can only protect against overload if the operator has selected the configuration that matches how the crane is actually set up on site. If the input doesn’t match reality, the system’s warnings are based on a fiction.

Before mobilizing a crane, lift planners and site engineers should confirm outrigger clearance and ground bearing capacity so the correct chart section is planned for in advance.

Site Inspections

Step by Step: Cross-Referencing a Planned Lift Against the Chart

1. Determine the actual load weight. Confirm this from the manufacturer’s data plate, shipping documents, or engineering drawings rather than an estimate.
2. Add rigging gear weight. Slings, shackles, spreader bars, lifting beams, and the hook block itself all add weight that must be included in the total lifted weight, not treated as separate from it.
3. Establish the working radius. Measure the horizontal distance from the crane’s planned center of rotation to the load’s final and pick-up positions. Use the larger of the two radii for chart reference.
4. Select the correct chart page. Match outrigger configuration, counterweight setup, and boom length to what will actually be used on site.
5. Find the capacity at that radius. Read across the row for the measured radius under the matching boom length column.
6. Compare total lifted weight to chart capacity. The chart capacity must exceed the total lifted weight (load plus rigging) by the margin required under the relevant lift plan and site safety procedures.
7. Check for derating conditions. Confirm whether wind speed, load dynamics (such as swinging or side-loading), or ground conditions require reducing the usable capacity below the printed chart number.

This process is standard across UAE lift planning and should be documented in the method statement for every critical or non-routine lift.

Common Load Chart Reading Mistakes

Using the wrong outrigger configuration column. Reading a full-extension chart when the crane is set up on reduced outrigger spread overstates available capacity and is one of the leading contributors to crane instability incidents.

Not accounting for rigging gear weight. Treating the chart capacity as available purely for the payload, without subtracting slings, shackles, and the hook block, results in an effective overload even though the chart appeared to show margin.

Ignoring wind and dynamic load derating. Chart capacities generally assume static, vertical lifts in calm conditions. Wind loading on the crane structure and the suspended load, along with dynamic effects from swinging, sudden stops, or uneven ground, can reduce safe capacity well below the printed number. Manufacturers typically publish separate wind speed limit tables or in-cab warnings; these must be checked alongside the main chart.

Measuring radius incorrectly. Radius must be measured from the crane’s actual center of rotation, not from the outrigger pad or the crane’s outer edge. A miscalculated radius shifts the lift into a different, and possibly non-existent, row on the chart.

Assuming tonnage rating equals available capacity at any radius. A “100-ton crane” only lifts 100 tons under one specific configuration, almost always at minimum radius. At any greater radius, capacity is lower, sometimes dramatically so.

how to choose the right crane tonnage

Why Every Lift Plan Must Reference the Specific Crane’s Actual Chart

Load charts are specific to the individual crane model, and in some cases to the specific unit, based on its configuration, counterweight package, and rigging setup. A rule of thumb, such as assuming a crane can lift a fixed percentage of its rated tonnage at “typical” radius, is not a substitute for the manufacturer’s published data.

Lift plans, whether for routine picks or complex, non-routine lifts, should reference the load chart for the exact crane being mobilized, the exact boom configuration planned, and the exact outrigger and counterweight setup that will be used on site. A qualified lift planner or rigger reviews this alongside a site inspection to confirm ground conditions can support the crane’s outrigger loads at the required configuration.

Contacting the crane provider’s engineering or lift planning team before mobilization helps confirm the correct chart, configuration, and any site-specific derating factors apply to the job.

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FAQ

Is a load chart the same as a crane’s maximum rated capacity?
No. The maximum rated capacity is a single figure achieved only at minimum radius with a specific boom and configuration. The load chart shows how capacity changes across the full range of radii and boom lengths the crane can achieve.

Do all cranes of the same tonnage have identical load charts?
No. Load charts vary by manufacturer, model, boom type, counterweight package, and outrigger design, even among cranes marketed at the same maximum tonnage.

What happens if a lift exceeds the load chart capacity?
The crane’s rated capacity indicator should trigger a warning or automatic cutout before the limit is reached, provided the system has been set up with the correct configuration data. Operating beyond chart capacity risks structural failure or tip-over and is not permitted under standard lift planning practice.

Who is responsible for confirming the correct chart is used?
The lift planner, in coordination with the crane operator and site engineer, verifies the chart section against the actual site setup, load weight, and rigging configuration before the lift proceeds. This is typically documented in the lift plan and method statement.

Conclusion

Reading a load chart accurately means matching the planned lift’s real radius, boom configuration, outrigger spread, and total lifted weight (load plus rigging) against the manufacturer’s specific chart for that exact setup. Skipping any of these steps, or substituting a general assumption for the actual chart, is how overload incidents happen. For lift planning support or to confirm chart requirements for an upcoming project in the UAE, reach out to a crane provider’s engineering team before the crane mobilizes.

Mobile Crane vs Crawler Crane