Every piece of storage and handling equipment we sell carries a load figure. A shelf rated 75 kg. A cupboard housing rated 1.5 tonnes. A cage rated 500 kg. A lift table rated 2,000 kg. A pallet truck rated 2,500 kg. Those numbers look like they are all describing the same thing. They are not — and the difference between them is the difference between equipment that lasts fifteen years and equipment that fails in year two.
This guide explains what UDL, SWL, WLL and point load actually mean, where each one appears across storage and handling equipment, and the specific places we see the numbers get misread. It is written from a supplier's point of view: we supply the equipment and quote the manufacturers' figures. It is not structural engineering advice, and it does not replace a competent person where one is required.
UDL — uniformly distributed load
UDL is the weight a surface can carry when that weight is spread evenly across the whole surface. It is the figure quoted on almost every shelf, beam, worktop and drawer in industrial storage, and the word doing the work is uniformly.
Take a shelf rated 75 kg UDL — the standard figure on Bott Verso galvanised shelves. That means 75 kg spread across the full shelf area: a layer of boxes, a row of stock, a spread of components. It does not mean you can set a 70 kg casting in the middle of it and be within spec. Concentrating the load in the centre of a span produces far more bending in the shelf than the same weight distributed along it, and the shelf will deflect, then take a permanent set, long before it does anything dramatic.
A practical rule of thumb used across the industry: if the load sits in a single concentrated spot rather than spread out, treat the usable capacity as substantially lower than the UDL figure — and if the item is heavy and small-footprint, ask the manufacturer for a point-load figure rather than guessing at a fraction.
UDL is a static figure. It describes weight sitting still. It does not account for someone dropping a load onto the shelf, or for the shock of a pallet being set down hard by a truck. Loading dynamically into a static rating is one of the most common ways a shelf that was “within capacity” ends up bent.
Point load — the figure nobody asks for until it is too late
A point load (or concentrated load) is weight applied at a single small area rather than across the span. Machine feet, engine blocks, dies, transformer cores, a vice bolted to the front edge of a bench — all point loads.
Point-load capacity is always lower than the UDL figure for the same surface, sometimes dramatically so, and it depends on where on the span the load sits. Mid-span is the worst case; directly over a support is the best. If you know the equipment is going to carry concentrated loads, say so at enquiry stage. There is usually a heavier specification available, and it is far cheaper to buy it than to replace a deflected shelf run.
SWL and WLL — and why the industry moved from one to the other
These two get used interchangeably and should not be.
- WLL — Working Load Limit. The maximum load an item is rated by the manufacturer to carry in normal service. It is marked on the product, derived from testing and a design factor, and it does not change with circumstances.
- SWL — Safe Working Load. Historically the same idea, but assessed for a specific application by a competent person, who might reduce it below the WLL because of how the item is being used — a sling angle, a corrosive environment, a shock-loading risk.
Because “safe” implied a guarantee that no manufacturer can give across all conditions, most of the lifting industry has moved to WLL as the marked figure. You will still see SWL widely in the field, on older equipment and in everyday speech, and in most conversations the two are being used to mean the same thing. The practical point stands either way: the marked figure is a limit, not a target.
Both differ from breaking load (or minimum breaking load), which is the point at which the item fails. The gap between the two is the design factor — typically several times the working figure. That margin exists to absorb wear, misuse, shock and manufacturing variation. It is not headroom for you to spend.
Where each figure shows up in practice
Shelving and racking
Shelving is quoted per shelf as a UDL. Pallet racking is quoted two ways at once, and both matter: a per beam-pair UDL and a total bay load for the whole upright frame. It is entirely possible to be inside the beam figure on every level and outside the bay figure overall — that is the classic overload, and it is a frame failure rather than a beam failure. Our pallet racking buying guide works through both figures, and the racking and shelving range lists them per configuration.
Cantilever racking adds a third: a per-arm figure and a per-column figure. The GPC cantilever range runs at 200–250 kg per arm depending on specification, but you cannot simply multiply arm capacity by arm count to get column capacity — the column has its own, lower, total. See the cantilever racking guide and cantilever racking.
One more that catches people: the pallet itself has a rating. An EPAL Euro pallet carries a much lower racking figure than its headline static figure, because a pallet in a beam bay is acting as a bridge, not sitting on a floor. Racking design has to work to the racking figure. More on this in UK pallet sizes explained.
Workbenches and cabinets
Bench worktops are quoted as a UDL — 1,000 kg evenly distributed on the GPC modular benching, 250 kg on the fully welded stainless preparation benches. Cabinets carry two separate numbers that are routinely conflated: a per-drawer UDL and a total housing capacity. Bott Cubio drawers are rated 75 kg UDL each inside a housing rated up to 1.5 tonnes; the Verso 5-drawer mobile runs 50 kg per drawer against a 200 kg total. Filling every drawer to its individual limit can still exceed what the cabinet as a whole is designed to hold — and on a mobile cabinet it also raises the centre of gravity, which is why drawer blocking exists. See workbenches, drawer cabinets and the workbench buying guide.
Cages, containers and anything that gets lifted
Once equipment is lifted rather than stood on, you are in WLL/SWL territory and the rules change. GPC Grenadier security cages are rated 500 kg maximum load; the lift cages are rated 1,000 kg with forged lifting eyes. Roll containers typically work to around 500 kg. Lifting operations and lifting equipment carry duties under LOLER 1998 — planning, competent supervision, thorough examination — and lifting accessories such as slings have their own WLL that varies with the angle they are used at. A four-leg sling at a wide angle is not doing what a four-leg sling at a narrow angle is doing. If lifting is involved, get a competent person to plan it; this is one of the places where a supplier's spec sheet genuinely is not enough. See storage cages.
Trucks, stackers and lift tables
Handling equipment is rated by capacity at a stated load centre — and that qualifier is the whole story. A truck rated 2,500 kg is rated 2,500 kg with the load's centre of gravity at the standard distance from the heel of the forks. Push the load further out, or stack it tall and unevenly, and the effective capacity drops. On stackers the derating with lift height is steeper still.
Lift tables are rated as a straightforward capacity to BS EN 1570 — the GPC static lift tables run at 1,000 kg and 2,000 kg depending on model — but that capacity assumes the load is placed centrally on the platform. Off-centre loading on a scissor mechanism is not the same duty. Electric tugs are rated by the rolled load they can move, which is a different figure again from a lifted or carried load: the MT100110 at 1,000 kg and MT100215 at 1,500 kg are moving weight on wheels, not picking it up. See pallet trucks, stackers, lifters and loaders and the lift table guide.
Steps, platforms and castors
Access equipment is rated by maximum user weight including tools and materials — the tools count, and on a well-loaded tool belt they count for a lot. Castors carry an individual rating each, and the temptation is to multiply by four. Do not: on an uneven floor the load transfers unevenly between castors, and a braked castor under sustained side load behaves differently from a free-swivelling one. Manufacturers derate accordingly. See access platforms and steps and roll containers.
Six places load figures get misread
- Treating a UDL as a point-load allowance. The most common error, and the one that quietly bends shelves.
- Using a per-shelf or per-beam figure without checking the total. Bay totals and cabinet housing totals are separate limits.
- Ignoring the load centre on trucks and stackers. The headline capacity is conditional.
- Loading a static rating dynamically. Dropping a load in is not the same as placing it.
- Multiplying castor ratings by four. Load does not distribute evenly in the real world.
- Spending the safety margin. The gap between working load and breaking load belongs to wear, misuse and shock — not to you.
What to do with all this
Three habits cover most of it. Write the figure down where the equipment is — racking load notices exist for exactly this reason, and EN 15635 expects the rated loads to be displayed. Ask for the point-load figure whenever the load is heavy and small-footprint. And inspect: a shelf or beam that has taken a permanent set has already told you the loading is wrong, and under PUWER the duty to keep work equipment in a safe condition sits with the employer. Our guide to warehouse racking inspection covers what that looks like for racking specifically, and manual handling equipment covers the other half of the problem — the loads people are still lifting by hand.
Load figures are the most useful numbers on any spec sheet we publish, and the most frequently skimmed. If you are unsure which figure applies to a job, ask us before you order rather than after — and where the answer needs a structural engineer or a LOLER competent person, we will say so.
Frequently asked questions
What does UDL load mean?
UDL stands for uniformly distributed load. It is the maximum weight a shelf, beam or worktop can carry when that weight is spread evenly across the whole surface. It is a static figure — it describes weight sitting still, not weight being dropped or set down hard.
What is the UDL load capacity of a shelf?
It varies by product and span. As a reference point from our own range, Bott Verso galvanised shelves are rated 75 kg UDL each, roller shutter cupboard shelves 100 kg, GPC modular bench worktops 1,000 kg and fully welded stainless preparation benches 250 kg. Always work from the figure published for the specific configuration and span you are buying, because capacity falls as span increases.
Is UDL a dead load or a live load?
In structural terms a UDL can describe either — the term refers to how the load is distributed, not to what kind of load it is. On storage equipment the published UDL is a static rating for stored goods, so it behaves as a dead load. It does not include impact, shock or dynamic loading, which is why loads should be placed rather than dropped.
What is the difference between SWL and WLL?
WLL (Working Load Limit) is the manufacturer's rated maximum for an item in normal service, marked on the product. SWL (Safe Working Load) was traditionally an application-specific figure set by a competent person, which can be lower than the WLL because of how the item is used. Most of the lifting industry now marks WLL, since “safe” implied a guarantee that could not hold across all conditions.
What does SWL mean?
SWL means Safe Working Load — the maximum load an item of lifting equipment or an accessory is deemed safe to handle in a given use. It is a limit, not a target, and it is always well below the breaking load. Where lifting is involved, LOLER 1998 duties apply and the operation should be planned by a competent person.
How do you calculate a safe working load?
You do not calculate it from scratch as an end user — it is derived by the manufacturer from the breaking load and a design factor, and is verified by testing. What you do calculate is whether your actual load stays inside it: total weight, how it is distributed, where the centre of gravity sits, and whether the loading is static or dynamic. Where slings or angles are involved, or where the answer is not obvious, that assessment belongs to a competent person rather than a spec sheet.