Uniformly distributed load
Also called: UDL, uniform load, evenly distributed load
A uniformly distributed load (UDL) is a load whose weight is spread evenly over the full top deck of the pallet. Most published pallet ratings assume a UDL unless they say otherwise.
In depth: How much weight can a pallet hold? Static, dynamic and racking capacity
A layer of cases that covers the whole deck, all the same weight, is close to a UDL. A single machine on four feet is not.
Load types in pallet design
| Load type | Example | Effect on rating |
|---|---|---|
| Uniformly distributed, full coverage | Cases covering the whole deck | Baseline for most ratings |
| Partial uniform | Load covering only part of the deck | Lower |
| Line load | Rolls, beams or sheet goods on bearers | Lower, depends on position |
| Concentrated (point) load | Drums, machinery feet | Often much lower |
PDS offers all four as its "General Load Type" options.
How tests apply it
ASTM D1185 applies general-purpose test loads through a flexible airbag, which approximates a UDL with no stiffness of its own. ISO 8611 nominal-load tests use rigid load applicators. The Virginia Tech Center for Packaging and Unit Load Design notes that the two methods can give significantly different results for some pallets.
Why it matters
If your load is not uniform, a UDL rating overstates what the pallet can carry. Real case loads also have some stiffness, which can help (load bridging).
On a spec sheet or RFQ
Say "uniformly distributed, full deck coverage" only if it is true. Otherwise give the footprint of the load, where it sits, and the weight on each bearing area.
Common confusions
"Evenly stacked" is not the same as uniformly distributed. A pallet of heavy product in the center and light product at the edges is not a UDL.
Related
- GlossaryConcentrated loadA concentrated load is a load that bears on one or a few small areas of the pallet deck instead of spreading over it, such as drums, machinery feet or a coil. It usually gives a much lower safe load than the same weight spread evenly.
- GlossaryLoad bridgingLoad bridging is the effect of a stiff unit load spanning across the pallet's weak points, so the packaged product carries part of the load and the pallet deflects and stresses less than it would under a flexible load of the same weight.
- GlossarySafe loadSafe load (safe working load, SWL) is the largest load a pallet should carry in a given support condition, set well below the load that breaks it. Test standards divide the ultimate load by a safety factor, and PDS uses reliability-based safety levels.
- GuidesHow much weight can a pallet hold? Static, dynamic and racking capacityIt depends on how the pallet is supported. A typical 48 × 40 wood pallet safely carries about 1,500 to 2,800 lb (680 to 1,270 kg) in racking or on forks, and several times that on a flat floor. A EUR pallet is rated 1,500 kg. Only the manufacturer's rating for your support condition is authoritative.
- StandardsASTM D1185: test methods for palletsASTM D1185 is the US test method for pallets and related structures (skids, bases, platforms and bins). Static tests estimate stiffness, strength and safe working loads; dynamic tests estimate durability in handling. Retailers such as Home Depot accept an ASTM D1185 test as an alternative to a PDS report.
More in Performance and engineering
- GlossaryCreepCreep is the gradual increase in a pallet's deflection while a load stays on it over time. Wood creeps, and plastic creeps much more, especially when warm, so racked pallets sag more after days or weeks than when first loaded.
- GlossaryDeflectionDeflection is the amount a pallet bends or sags under load, measured at the point of greatest movement. Racking limits are commonly about 2% of the span, and automated systems often require 0.5 in (13 mm) or less.
- GlossaryDurabilityDurability is a pallet's ability to survive repeated handling, measured as the number of trips or handling cycles before it needs repair or is scrapped. It is driven by fastener quality, lead board width, member thickness and species density.
- GlossaryDynamic loadDynamic load is the weight a pallet can safely carry while it is being moved, supported on forklift tines, a pallet jack or a conveyor. It sits between the static rating and the racking rating.
- GlossaryLoad capacityLoad capacity is the maximum weight a pallet can safely carry under a stated support condition. It is always quoted per condition: static (on the floor), dynamic (on forks or a pallet jack) and racking (spanning rack beams), and the racking figure is usually the lowest.
- GlossaryPallet tripA pallet trip is one complete cycle of use: the pallet is loaded, moved through the supply chain, unloaded, and made available for its next load. Durability and cost per use are both measured in trips.
Last reviewed 2026-09-24. 266 words.