How to Measure Wire Mesh
Last reviewed on October 3, 2026
If you need to replace a screen, match an existing filter or check a delivery against the order, you can identify most stainless steel mesh with a ruler, a magnifier and a micrometer. This guide shows how to measure mesh count, wire diameter and opening size for woven mesh, how to measure welded mesh, expanded metal and perforated sheet, and what you can and cannot tell about the grade.
Tools
- Steel rule with an inch scale (mesh count is defined per inch) — a mm rule works too if you convert.
- 10× loupe or magnifier — essential above about 30 mesh. A phone camera in macro mode next to a rule also works.
- Micrometer for wire diameter (a digital caliper is fine for wire thicker than about 0.5 mm).
- For very fine mesh: a measuring microscope or a scanner image at known resolution.
Step 1: Count the Mesh
Mesh count is the number of openings (equivalently, wires) per linear inch.
- Lay the rule along one wire so the zero mark sits on the centre of a cross wire.
- Count the openings until you reach the 1-inch mark. That number is the mesh count in that direction.
- Turn the rule 90° and repeat. If the counts differ (for example 18 and 16), the mesh is rectangular and is written 18 × 16.
Fine mesh: counting 100+ openings by eye is error-prone. Count across 1/4 inch and multiply by 4, or count across 10 mm and multiply by 2.54 (10 mm × 2.54 = 25.4 mm = 1 inch). Counting over a longer distance and dividing gives a more accurate answer than counting a short distance and multiplying.
Metric listings: some European suppliers give "openings per cm". Multiply by 2.54 to get mesh per inch.
Step 2: Measure the Wire Diameter
- Pull a single wire from a cut edge, or measure on the cloth at a straight section between crossings.
- Use light, consistent micrometer pressure; fine wire flattens easily under caliper jaws.
- Cross-check: unflattened plain-weave cloth is roughly twice the wire diameter thick, because the wires lie on top of each other at each crossing. Calendered (rolled-flat) cloth will be thinner.
Wire may be listed in decimal inches, millimetres or a gauge number; the wire gauge chart converts between them.
Step 3: Calculate (and Check) the Opening
For square-weave mesh: opening (mm) = 25.4 ÷ mesh − wire (mm). You can then confirm with the loupe against a fine scale, or measure the opening directly on a scanned or microscope image.
Worked example: you count 30 openings per inch in both directions and measure the wire at 0.30 mm. Opening = 25.4 ÷ 30 − 0.30 = 0.547 mm (547 µm), open area ≈ 42%. Look it up or check other combinations in the mesh size chart and calculator.
Step 4: Identify the Weave
| What You See Under Magnification | Weave |
|---|---|
| Square openings; each wire goes over one, under one | Plain weave |
| Square openings with visible diagonal lines; wires go over two, under two | Twill weave |
| Heavy wires in one direction, fine wires packed tightly side by side in the other; no square holes visible when you look straight through | Dutch weave (plain or twilled) |
| Wires with regular waves or bends formed before weaving, usually coarse | Crimped mesh |
A Dutch weave cannot be identified by mesh count alone — record both counts (for example 24 × 110) and ask the supplier for the tested micron rating. See woven wire mesh for more on weaves.
Step 5: Identify the Grade (304 or 316?)
You cannot tell 304 from 316 by eye, and the magnet test is unreliable: cold work from drawing and weaving can make both grades slightly magnetic, while some non-stainless coatings are not. Reliable options are:
- The mill test certificate supplied with the material.
- A handheld XRF analyser (many metal stockists and scrap yards have one).
- A molybdenum spot-test kit, which distinguishes molybdenum-bearing 316 from 304.
If the mesh will see salt or chlorides and you cannot confirm the grade, assume 304 and replace it with certified 316. Background in 304 vs 316 stainless mesh.
Measuring Welded Mesh
- Spacing: measure centre to centre across several openings (for example across 10 openings and divide by 10) in both directions.
- Wire: measure with a caliper and convert to gauge if needed.
- Clear opening: spacing minus wire diameter. A "1/2″" mesh with 0.041″ wire has a clear opening of about 0.46″ (11.7 mm).
Measuring Expanded Metal and Perforated Sheet
- Expanded metal: measure the short way of the diamond (SWD) and long way of the diamond (LWD) from the centre of one bond (joint) to the centre of the next, plus strand width and sheet thickness. See expanded metal mesh.
- Perforated sheet: record hole diameter, pitch (centre to centre), pattern and thickness. For round holes on a 60° staggered pattern, open area ≈ 90.7 × (hole ÷ pitch)² %; on a straight (square) pattern, ≈ 78.5 × (hole ÷ pitch)² %. See perforated sheet.
Recording What You Measured
A complete description lets any supplier quote the same material: "304 stainless woven wire cloth, plain weave, 30 × 30 mesh, 0.30 mm wire (≈0.55 mm opening), 1 m wide roll." For screens, add the frame size and how the mesh is fixed; for filters, the required micron rating and the fluid.