Leather Thickness Converter (oz ↔ mm)
Convert leather weight between ounces and millimeters and see the typical use for that thickness range.
| Weight | Typical use |
|---|---|
| 1–2 oz | Linings, wallet interiors |
| 2–3 oz | Wallets |
| 4–5 oz | Bags, small goods |
| 6–7 oz | Knife sheaths |
| 8–10 oz | Belts |
| 10–12 oz | Holsters, heavy straps |
Hides vary across their own area, which is why weights are sold as ranges (like "4/5 oz") rather than one exact number.
How it works
Leather in the US is sold by weight in ounces, where each ounce equals 1/64 inch, or 0.4 mm, of thickness. Enter a number in either ounces or millimeters and the calculator converts it to the other unit, then matches it against the common use ranges leatherworkers actually shop by, from thin lining leather up to heavy holster-grade hide.
Worked example: 5 oz leather. Multiply by 0.4 mm and you get 2 mm thick, which lands in the 4 to 5 oz range used for bags and small goods. Go the other direction and 1.6 mm of leather divides back out to 4 oz, right at the edge of that same range, which is why 4/5 oz leather is the standard pick for a lot of beginner bag and pouch projects.
FAQ
Why is leather measured in ounces instead of just millimeters?
It's a holdover from how tanneries have historically graded hide, and the ounce system stuck because most suppliers, patterns, and stitching charts still list weight in oz. Once you know the 0.4 mm-per-ounce conversion, you can work comfortably in whichever unit your calipers or your supplier uses.
Why does my supplier list a range like "8/9 oz" instead of one number?
A single hide isn't uniform thickness across its whole surface, the belly and edges run thinner than the back and shoulder. Tanneries split leather to a target range rather than an exact figure, so "8/9 oz" means you can expect thickness anywhere in that band.
Can I combine two thinner weights to build up a project?
Yes, gluing two pieces together (called laminating) is a common way to get a custom thickness, for example two pieces of 4 oz glued face to back give you roughly an 8 oz feel with a finished front and back surface on both sides.
What thickness should a first project use?
For something like a card holder or simple wallet, 2 to 3 oz is forgiving to cut and fold by hand. Save the 8 oz and up weights for belts and structural pieces once your stitching and edge work are more consistent.
For choosing a hide and reading these weights on a supplier's cut, see leather weights and thicknesses explained, choosing your first hide, and full grain, top grain, and genuine leather grades explained.