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Washer gauge to mm sizing chart

Washers are sized by gauge (Standard Wire Gauge, SWG) which measures the thickness of the washer — not the diameter. Lower gauge = thicker washer. A 10g washer is thicker than a 22g washer. The chart below covers every standard washer gauge from 8g to 24g with the matching thickness in millimetres and inches.

Gauge	Thickness (mm)	Thickness (inch)
8g	4.06 mm	0.160"
10g	3.25 mm	0.128"
11g	2.95 mm	0.116"
12g	2.64 mm	0.104"
13g	2.34 mm	0.092"
14g	2.03 mm	0.080"
15g	1.83 mm	0.072"
16g	1.63 mm	0.064"
17g	1.42 mm	0.056"
18g	1.22 mm	0.048"
19g	1.02 mm	0.040"
20g	0.91 mm	0.036"
21g	0.81 mm	0.032"
22g	0.71 mm	0.028"
23g	0.61 mm	0.024"
24g	0.56 mm	0.022"

Quick tips

Lower gauge = thicker washer. 10g is a heavy structural washer; 22g is a thin spacer.
Washer gauge measures thickness, not diameter. The hole size and outside diameter are separate specs — both shown on every BNA washer product page.
Pairing with bolts: typical flat washers for M8–M10 bolts are 14g; for M10–M12 use 13g or thicker.

Browse our washers — Find the right thickness, hole size and finish in our full washer range. Flat, mudguard, spring, lock and more.

Not sure which washer thickness to pick? Tell us what you're bolting and what type of washer (flat, mudguard, spring, lock) — we'll match the right gauge. Contact us or call 07 3192 9800.

Thicknesses based on Standard Wire Gauge (SWG). Information sourced from various suppliers and provided as a guide only.