How to Calculate Caster Load Capacity (and How to Measure a Caster)
The most common mistake in caster selection is dividing the total weight by the number of casters. No floor is perfectly flat: when a cart rolls over a threshold or a dip, for a moment the whole load rests on three casters. So the calculation is:
Required capacity per caster = (Cart weight + Load) ÷ (Number of casters − 1)
Worked examples
| Equipment | Cart + load | Casters | Capacity needed per caster |
|---|---|---|---|
| Loaded filing cabinet | 120 kg (265 lb) | 4 | 40 kg (88 lb) |
| Service cart | 240 kg (530 lb) | 4 | 80 kg (176 lb) |
| Warehouse shelf trolley | 600 kg (1,320 lb) | 4 | 200 kg (441 lb) |
| Machine moving dolly | 2,400 kg (5,290 lb) | 4 | 800 kg (1,764 lb) |
| Heavy mould cart | 6,000 kg (13,230 lb) | 6 | 1,200 kg (2,646 lb) |
If the cart takes regular impacts (ramps, uneven floors, towing at speed), add a margin of roughly 20–30% to the result. On hand-pushed carts, larger wheels and ball bearings make pushing easier as the load per caster rises.
Which product range for which load?
| Load per caster | Product range |
|---|---|
| 30–65 kg (66–143 lb) | Furniture casters |
| 50–300 kg (110–660 lb) | Industrial casters |
| 80–1,000 kg (175–2,200 lb) | Heavy duty casters |
| 400–3,500 kg (880–7,700 lb) | Extra heavy duty casters |
Measuring a caster for a replacement or equivalent
If you are replacing an existing caster, take these measurements:
- Wheel diameter: The outside diameter of the wheel (for example 100 mm / 4 in).
- Wheel width: The width of the tread that touches the floor.
- Overall height: From the floor to the mounting surface. If the new caster is a different height, the cart will stand crooked.
- Fitting size: Plate size and bolt hole spacing for a top plate caster; stem diameter and length for a threaded stem; hole diameter for a bolt hole caster; stem diameter and length for a plug-in stem.
- If only the wheel is being replaced: Hub length and axle bore diameter. Then a replacement wheel is all you need, not a whole caster.
All of these dimensions are listed on our product pages. If measuring is a hassle, send us a photo of the caster or the code printed on it, and we will find the equivalent. Request a quote →