📏 Leather Thickness Converter

Leather thickness is traditionally measured in ounces, where 1 oz equals 1/64 inch. Enter a thickness in any unit to convert it.

Amount

Unit

The ounce is a thickness, not a weight

One ounce of leather means 1/64 of an inch of it. The name survives from the days when a square foot of hide at that thickness weighed about an ounce, and everything the converter does follows from the one constant:

1 oz = 1/64 in = 25.4 / 64 = 0.396875 mm
mm = oz × 0.396875      oz = mm / 0.396875
in = mm / 25.4            8 oz = 3.175 mm = 0.1250 in

Whichever unit you pick, the amount is converted to millimetres first and the other two are read back from that. The trade shorthand of 0.4 mm per ounce is fine for talking but overstates by 0.8 %: it turns 8 oz into 3.2 mm instead of 3.175, and by 12 oz the gap is a tenth of a millimetre.

What each weight is used for

Weight	Thickness	Typical use
2–3 oz	0.79–1.19 mm	Linings, wallet interiors, garment
4–5 oz	1.59–1.98 mm	Wallets, watch straps, small bags
6–7 oz	2.38–2.78 mm	Bags, sheaths, lined belts
8–9 oz	3.18–3.57 mm	Belts, holsters, dog collars
10–12 oz	3.97–4.76 mm	Heavy straps, tack, tooling blanks

Hides are sold as a range — 5–6 oz, not 5.5 oz — because thickness varies across one side by an ounce or more, thinning towards the belly. Measure the actual part with a gauge or calipers before you size a beveler, a punch or a snap.

Frequently asked questions

How many mm is 8 oz leather?

3.175 mm, which suppliers round to 3.2 mm. That is 1/8 in, the usual weight for a belt.

How thick is 4–5 oz leather?

1.59 to 1.98 mm, near enough 1/16 to 5/64 in. It is the standard range for wallets and watch straps: firm enough to hold a burnished edge, thin enough to fold without skiving.

How do I convert mm to ounces of leather?

Divide by 0.396875. A hide measuring 2.4 mm is 6.05 oz, so it would be sold as 5–6 oz or 6–7 oz stock.