Journal · From the Bench
Leather thickness chart, oz to mm
Published 9 October 2026 · Gordon Mielke
Why leather is measured in ounces, a full oz-to-mm chart, and which thickness suits which piece at the bench.
If you've ever read a leather spec and seen "3–4 oz" next to a wallet, you might reasonably wonder why leather is weighed like coffee beans. It isn't, really. In leatherwork, "ounce" is a measure of thickness. This entry gives you a leather thickness chart in ounces, inches and millimetres, explains why weights always come as a range, and shows which thickness I use for which piece at the bench in East Vancouver.
What "ounce" means in leather
The convention used across North American leathercraft is that one ounce of leather weight equals about 1/64 of an inch of thickness. Tandy Leather's published weight chart states it as "1 oz = ~1/64 inch = ~0.4 mm", which means a 4 oz leather is about 1/16 inch, or 1.6 mm, thick.
The maths is simple: an inch is 25.4 mm, and 25.4 divided by 64 is just under 0.4 mm. So to convert, multiply ounces by 0.4 to get millimetres, or divide millimetres by 0.4 to get ounces. It's an approximation, but it's the one the whole trade uses.
Leather thickness chart: ounces to inches and millimetres
| Weight (oz) | Thickness (inches) | Thickness (mm) | Typical uses (Tandy Leather chart) |
|---|---|---|---|
| 1–2 oz | 1/64"–1/32" | 0.4–0.8 mm | Lining, book covers, small inlays |
| 2–3 oz | 1/32"–3/64" | 0.8–1.2 mm | Wallet interiors, watch straps |
| 3–4 oz | 3/64"–1/16" | 1.2–1.6 mm | Wallet exteriors, small bags |
| 4–5 oz | 1/16"–5/64" | 1.6–2.0 mm | Clutch bags, notebook covers |
| 5–6 oz | 5/64"–3/32" | 2.0–2.4 mm | Satchels, medium belts |
| 6–7 oz | 3/32"–7/64" | 2.4–2.8 mm | Tool pouches, sturdy belts |
| 7–8 oz | 7/64"–1/8" | 2.8–3.2 mm | Heavy belts, holsters |
| 8–9 oz | 1/8"–9/64" | 3.2–3.6 mm | Saddlery, sheaths |
| 9–10 oz | 9/64"–5/32" | 3.6–4.0 mm | Harness work, heavy straps |
| 10+ oz | 5/32"+ | 4.0+ mm | Very heavy-duty gear |
Keep this leather thickness chart handy when you're comparing specs between makers: once you translate ounces to millimetres, it's much easier to picture what you're getting.
Why leather weights always come as a range
You'll almost never see leather sold as exactly "4 oz". It's "3–4 oz" or "4–5 oz". That's because a hide is a piece of an animal, not a sheet of plastic. Tanneries run hides through a splitting machine to bring them to a target thickness, but as Tandy Leather's buying guide puts it, each animal is different and there is always a slight thickness variation throughout the hide. That's one reason I check every hide by hand before cutting and place pattern pieces according to where the leather is strongest; more on that in cutting leather from a full hide.
How thickness is measured
Leatherworkers use a thickness gauge: a spring-loaded dial or a slotted pocket gauge you slide the edge of the leather into. It's worth measuring in more than one spot on a hide, for exactly the reason above.
Which thickness I use for which piece
Thicker isn't automatically better. A wallet built from belt leather would be bulky in a pocket and wouldn't fold cleanly. The right thickness depends on what the piece has to do. Here's how it works out across the Rogue Artisan range, as described on each product page:
- Card holders: 2–3 oz. Slim enough not to feel bulky in a front jeans pocket, but still holds its shape. See card holders.
- Field notes covers: 3–4 oz (1.2–1.6 mm). Stiff enough to protect the pages, thin enough to bend with the notebook. See field notes covers.
- EDC trays: 4–5 oz. Enough body to hold the tray walls up.
- Belts: 8–10 oz veg-tan, or roughly 8 oz Chromexcel. A belt needs the body to hold a buckle without folding at the holes. See custom leather belts.
Thickness and the finished piece
The number on the hide isn't the number in your pocket. Folds, layers and pockets add up, which is why wallet interiors are often thinner leather than exteriors, and why I skive (thin) leather at folds and overlaps so the finished piece lies flat. That's covered in skiving and edge finishing. If you're choosing between a bifold, long wallet and card holder, the wallet sizing guide covers how thickness and layout affect pocket feel.
Thickness, break-in and how leather ages
Heavier veg-tan takes longer to break in. A 10 oz belt is a serious strap; it won't flop, and it takes some weeks of daily wear to soften. An 8 oz belt is more comfortable from day one but shows creases sooner. Lighter leathers soften quickly and pick up patina fast, since there's less material to change. None of that is good or bad; it's a choice about how you want a piece to feel now and in five years.
Not sure what thickness suits the piece you have in mind? Every Rogue Artisan piece is made to order, so thickness is part of the conversation. Call (250) 719-1332 or email rogueartisan@outlook.com.
Frequently asked questions
How thick is 1 oz leather?
About 1/64 of an inch, or roughly 0.4 mm. To convert, multiply ounces by 0.4 to get millimetres.
How thick is 4 oz leather in mm?
About 1.6 mm, or 1/16 of an inch. Tandy Leather's chart uses 4 oz leather as its own worked example.
Why is leather thickness given as a range like 3–4 oz?
Because hides vary naturally across their surface. Tanneries split hides to a target thickness, but there's always some variation, so weights are sold as a range.
What thickness leather is best for a wallet?
Wallet exteriors are commonly 3–4 oz and interiors 2–3 oz. Rogue Artisan card holders use 2–3 oz leather so they stay slim in a front pocket.
What thickness is a good leather belt?
Rogue Artisan belts use 8–10 oz full-grain vegetable-tanned leather, or roughly 8 oz Horween Chromexcel, so the strap holds a buckle without folding at the holes.