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What size crane do I need for my lift?
What size crane do you need? It depends on three measurements: the total weight being lifted, how far from the crane it has to go, and how high it has to clear. A crane’s name, such as a 50 tonne or 100 tonne crane, is its maximum capacity at the shortest reach, so the crane you need is almost always much bigger than the weight of the load.
In short
- Start with the total weight: the load plus the hook block and all the lifting gear.
- Measure the radius: from the centre of the crane’s slew to the load’s furthest position.
- Check the height: what the boom and load must clear on the way.
- Read the capacity at that radius and boom length from the crane’s load chart, not its headline tonnage.
- The final choice is made by a competent appointed person as part of the lift plan.
We plan lifts and supply cranes of every type for crane hire and contract lifting. This guide explains how crane size is worked out, so you can give us the right information and understand the recommendation you get back.
The three measurements that decide crane size
Every crane size starts with the same three numbers. Getting them right at the start avoids a crane that is too small on the day, or one that is bigger, and costlier, than needed.
Weight
The weight is not just the load. It includes the hook block, slings, shackles, spreader beams and any other lifting accessories between the hook and the load. For a machine, the weight should come from the manufacturer’s data or a weighbridge ticket rather than an estimate, and the position of its centre of gravity matters as much as the figure itself.
Radius
The radius is the horizontal distance from the centre of the crane’s slew ring to the centre of gravity of the load. It is measured at the furthest point the load reaches, which may be where it is picked up, where it is set down or somewhere in between.
Height
Height decides the boom length. If the load has to go over a building, a roof edge or scaffolding, the boom must be long enough to clear it with the load hanging below. A longer boom at the same radius usually means less capacity.
Why a 50 tonne crane will not lift 50 tonnes
This is the point that surprises most people. A crane’s headline capacity is the most it can lift in its most favourable set-up, which in practice is rarely the set-up the job needs.
The load chart
Every crane has a load chart that lists its capacity at each radius and boom length. The headline figure applies only at the shortest radius, with the full counterweight fitted and the outriggers fully extended. As the radius grows, the capacity falls quickly, and at long reach a crane may lift only a small fraction of its headline tonnage.
Configuration matters
The same crane has different charts for different set-ups: how much counterweight is fitted, how far the outriggers are extended, whether a jib is used and which way the crane is slewing. A crane squeezed into a tight space with outriggers part-extended can have far less capacity than the same crane on open ground.
A worked illustration
Take a 5 tonne load, with 250 kilograms of lifting gear, to be placed 20 metres from where the crane can stand. The crane needed is one whose chart shows at least 5.25 tonnes at 20 metres, at the boom length needed to clear any obstruction. Depending on the obstruction, that can mean a crane with a headline capacity many times the weight of the load.
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You can see this on our crane pages. The load chart summary for the Liebherr LTM 1100-5.2, a 100 tonne crane, shows 82.6 tonnes at 3m radius but 12.9 tonnes at 20m, on its main boom with full counterweight.
How size is measured for different types of crane
Not every crane is sized the same way. The measure that matters depends on the type, and choosing the type is often the first step. Our guide Types of crane compares them side by side.
Mobile cranes
All-terrain cranes and city cranes are named by maximum capacity in tonnes, from about 10 tonnes for the smallest city cranes to over 1,000 tonnes for the largest all-terrain cranes. Capacity at radius, from the load chart, is what decides the size.
Tower and mobile tower cranes
Tower cranes and mobile tower cranes are chosen by jib length and the capacity at the jib tip, because the heaviest load at the furthest radius usually decides the crane.
Loader cranes
Loader cranes are rated in tonne-metres, the load multiplied by the reach, so how close the lorry can park is as important as the weight.
Compact cranes
Spider cranes and pick and carry cranes are sized by capacity, but the access often decides first: the crane has to fit through the door and the floor has to take it. Pick and carry cranes also have separate duties for travelling with the load.
Other factors that change the crane size
Weight, radius and height give a first answer. The site then adjusts it.
Where the crane can stand
Every metre closer the crane can set up reduces the radius, and often the crane size. A set-up position that looks slightly awkward can save a size or two of crane compared with one that is easy but further away.
Ground conditions
A bigger crane puts bigger loads through its outriggers. Soft ground, buried services or a suspended slab can limit where a crane stands, or which crane can be used at all.
Access and space to rig
The right size of crane still has to reach the set-up position and have room for its outriggers, counterweight and any lorries bringing ballast. On tight sites this can point towards a different type of crane rather than a different size.
Wind and the shape of the load
Large, flat loads such as panels and plant with big surfaces catch the wind, and the lift plan sets wind limits accordingly. There is no single wind figure for a crane; it depends on the crane and the load.
Two-crane lifts
Some loads are lifted by two cranes together, or turned over in the air using a second crane. These tandem lifts need careful planning because the load shares between the cranes change during the lift.
How the crane size is confirmed
An estimate from the three measurements is a good start, but the final choice belongs in the lift plan.
The lift plan
Under regulation 8 of the Lifting Operations and Lifting Equipment Regulations 1998 (LOLER), every lifting operation must be properly planned by a competent person, appropriately supervised and carried out in a safe manner. The HSE’s LOLER guidance explains what that means in practice, and the BS 7121 codes of practice set out how an appointed person plans a crane lift.
What to send us
- The weight of the load, and its dimensions and lifting points if you have them
- A site plan or photos showing where the crane could stand and where the load goes
- Anything the load has to go over, such as buildings, roofs or scaffolding
- The access route for the crane and any known ground conditions
Where the lift is complex or the site is unfamiliar, a site survey confirms the set-up position, the radius and the ground before the crane is booked.
Crane hire or contract lift
On a contract lift we plan the lift and choose the crane. On a crane hire, the hirer plans the lift and chooses the crane, and we can advise. Our guide to crane hire or a contract lift explains the difference.
Common questions
How do I work out what size crane I need?
Find the total weight including lifting gear, measure the radius from where the crane can stand to the load’s furthest position, and note anything the load must clear. The crane needs enough capacity at that radius and boom length on its load chart.
Can a 50 tonne crane lift 50 tonnes?
Only at its shortest radius, with full counterweight and outriggers fully extended. At the radius most jobs need, its capacity is much lower, so the crane is chosen from its load chart rather than its name.
What is the radius of a crane lift?
The horizontal distance from the centre of the crane’s slew ring to the load’s centre of gravity, at the furthest point the load reaches during the lift.
Do I need to include the weight of the lifting gear?
Yes. The hook block, slings, shackles and any spreader beam all count towards the load the crane lifts.
Who decides what size crane is used?
The appointed person who plans the lift. On a contract lift that is us; on a crane hire it is the hirer, who can ask us for advice on the crane.
Get help choosing the right crane
Call us on 0800 008 6096 or email office@synergy-lifting.co.uk. Send us the weight, a site plan or photos and where the load needs to go, and we will recommend the right type and size of crane.
Find out more about our crane hire and contract lifting, lift and shift and machine delivery and installation services.
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