Last updated 2026-11-12
Caster wheel size chart: how to measure for replacement
Wheel diameter, tread width, overall height and mounting dimensions in mm and inch — where each number comes from, the conversion chart, and how to match a size to a load rating.
Five numbers identify a replacement caster: wheel diameter, tread width, overall height, and the mounting dimensions — stem diameter and length, top plate and hole centres, or the tube bore for expanding stems. Measure the old caster in millimetres, read the size chart below for the nominal inch equivalent, and match the load rating before you order. This guide shows where each number comes from — and the measuring mistakes that send the wrong wheel to your door.
The five measurements that identify a caster
- Wheel diameter — measure straight across the centre of the wheel, tread edge to tread edge, with the wheel still mounted: lay a ruler flat across the wheel face or use calipers. Record millimetres first; inch sizes in catalogues are nominal labels, the millimetre value is the specification.
- Tread width — the width of the tread face that contacts the floor, not the overall width across the fork. Two wheels can share one diameter and carry quite different loads, and the fork is always wider than the tread.
- Overall height — from the floor to the top of the plate (or to the mounting face of the stem). This is not the wheel diameter: two casters with 75 mm wheels can stand 90 mm and 105 mm tall. A replacement taller than the original tilts the equipment; shorter lowers it.
- Mounting dimensions — which of the four mounting families you have decides what to measure: thread diameter, pitch and usable length for threaded stems; the tube's inner diameter for grip-ring and expanding stems; plate length, width and hole centres for top plates; the bore diameter for top-hole casters. The mounting types guide walks through each family.
- Load per caster — the size chart does not set capacity. Two 100 mm wheels can be rated 100 kg and 150 kg depending on tread, bracket and bearings. Divide the equipment's total weight by the casters that carry it and apply a 1.3–1.5 safety factor — the load capacity chart shows the arithmetic.
Caster wheel size chart: mm to inch
Wheel sizes are specified in millimetres and sold under nominal inch labels. The chart pairs the two and shows where each size typically works, with the JLS catalogue column filled from our own 62-model range (40–100 mm, light and medium duty).
| Wheel Ø (mm) | Nominal (inch) | Typical applications | JLS catalogue |
|---|---|---|---|
| 40 | 1.6" | Small displays, light fixtures, compact furniture | JLS-0-HB — 100 kg |
| 50 | 2" | Office chairs, displays, light trolleys and stands | 14 models — 30–60 kg |
| 75 | 3" | Trolleys, service carts, medical equipment | 16 models — 100–150 kg |
| 100 | 4" | Trolleys, racks, medium industrial equipment | 31 models — 100–150 kg |
| 125 | 5" | Platform trucks, hospital beds, heavier carts | — |
| 150 | 6" | Waste and linen bins, warehouse trucks | — |
| 200 | 8" | Industrial platform trucks, heavy racking | — |
Two cautions when reading any size chart. Inch labels are nominal — a "2 inch" wheel in a metric catalogue is 50 mm exactly, and odd sizes such as 1.6" (40 mm) round awkwardly, so order by the millimetre value on the drawing. And beyond the size, capacity comes from the tread, bracket and bearings — a 100 mm / 150 kg caster is a different product from a 100 mm / 100 kg one.
How to measure each mounting type
- Threaded stem — measure the thread diameter at the root with calipers, confirm the pitch (a thread gauge, or the nut that fits the old stem), and the usable length from shoulder to tip. Stems with the same diameter but different pitches are not interchangeable. Example: JLS-2-SHP threaded-stem caster.
- Grip-ring / expanding stem — measure the inner diameter of the tube or socket the stem plugs into, never the tube's outside diameter. On seating, 7/16" × 7/8" grip-ring is the industry standard — our chair caster guide covers it in detail. On equipment tubes, the JLS-3-CH expanding-stem caster fits by bore diameter.
- Top plate — record the plate length × width, then the hole centres centre-to-centre in both directions and the bolt diameter. Two plates with the same outline can carry completely different hole patterns. Example: JLS-3-DBP top plate caster.
- Top hole / bolt hole — measure the central bore diameter and the bolt that passes through it, and confirm the overall height under the frame. Example: JLS-3-KCH top-hole caster.
Match the size to the load before ordering
A bigger wheel rolls more easily and crosses thresholds better — it does not carry more by itself. The load rating comes from the wheel material, bracket and bearings, and a brake option can change the bracket and the space it needs. The practical sequence: fix the overall height the frame allows, choose the wheel size that fits it, then check the load rating and brake — in that order. The 7-step selection guide puts size, load, floor and bearings into one sequence.
Common measuring mistakes
- Measuring the wheel with the ruler on an angle — the reading runs large. Keep it flat across the centre, or use calipers.
- Confusing overall height with wheel diameter — the fork and mounting add 20–40 mm to the wheel.
- Measuring the tube's outside diameter on grip-ring and expanding stems — the fit is on the bore inside.
- Comparing top plate outlines without checking hole centres in both directions.
- Recording a thread diameter without the pitch — M10 × 1.25 and M10 × 1.5 are different stems.
- Ordering by the nominal inch label only — confirm the millimetre value on the product drawing before the purchase order.
Put the five numbers in your inquiry — wheel Ø and width, overall height, mounting dimensions, load per caster — and you get a costed offer with the matching drawing, usually within 24 hours.
Frequently asked questions
How do I know what size caster I need?
Measure the old caster: wheel diameter, tread width, overall height and the mounting dimensions, then match the load rating. If there is no sample — new build or lost original — work from the frame: the overall height it allows, the mounting type it takes, and the load per caster.
How do you measure a caster wheel diameter?
Measure straight across the centre of the wheel from tread edge to tread edge, with the wheel still on the caster. Lay a ruler flat across the wheel face or use calipers, and record millimetres — inch labels are nominal.
What size caster wheels do trolleys use?
Light and medium-duty trolleys most commonly use 75–100 mm (3–4 in) wheels. Hospital beds and platform trucks run larger — 125 mm and up — to keep push effort low; our hospital bed caster guide covers that class in detail.
How do you convert caster wheel sizes between mm and inch?
1 inch = 25.4 mm. Common pairs: 50 mm = 2", 75 mm ≈ 3", 100 mm ≈ 4", 125 mm = 5". The inch figure is a nominal label — always confirm the millimetre value on the drawing before ordering.
Is a bigger caster wheel better?
Only up to the frame. Larger wheels roll more easily and handle thresholds better, but they raise the overall height and do not increase the load rating by themselves — that comes from the tread, bracket and bearings. Let the mounting height the frame allows decide the wheel size.
Zehong Dong — Technical sales manager, JIELISHI
Handles OEM and distribution enquiries for casters — load and mounting selection, sample approval, custom tooling and the production follow-up in between.