Leather thickness converter
An American guide says "4–5 oz leather" and you're stuck holding calipers wondering what that means. We know. Enter the ounces (a range works too) and instantly see millimetres, and which leather to buy.
Convert oz to mm
Leather is a natural material, so allow for a ±0.2 mm tolerance within a single hide.
Not sure about the thickness? Pick what you're making
We'll recommend a range in ounces and millimetres, plus matching leather in stock.
Complete leather thickness table
1 oz = 0.396875 mm · rounded to 0.1 mm| oz | mm | Typical use | In stock |
|---|---|---|---|
| 1–2 oz | 0.4–0.8 mm | Linings, interior padding, fine details | Thin (0.8–1.5 mm) → |
| 2–3 oz | 0.8–1.2 mm | Small pouches, fine leather goods | Thin (0.8–1.5 mm) → |
| 3–4 oz | 1.2–1.6 mm | Wallets, card holders, light bags | Thin (0.8–1.5 mm) → |
| 4–5 oz | 1.6–2.0 mm | Wallet exteriors, handbags, notebook covers, reinforced belts | Medium (1.6–2.5 mm) → |
| 5–6 oz | 2.0–2.4 mm | Soft bags, handbags, small dog collars | Medium (1.6–2.5 mm) → |
| 6–7 oz | 2.4–2.8 mm | Collars, leashes, lighter belts | Strong (2.6–4.0 mm) → |
| 7–8 oz | 2.8–3.2 mm | Belts, large dog collars, bag straps | Strong (2.6–4.0 mm) → |
| 8–9 oz | 3.2–3.6 mm | Sturdy belts, leashes, heavy-duty bags | Strong (2.6–4.0 mm) → |
| 9–10 oz | 3.6–4.0 mm | Sheaths/holsters, harness straps | Strong (2.6–4.0 mm) → |
| 10–12 oz | 4.0–4.8 mm | Saddles, harnesses, heavy sheaths | Extra strong (4.1 mm+) → |
| 12–14 oz | 4.8–5.6 mm | Soles, extreme-wear parts | Extra strong (4.1 mm+) → |
Why is leather thickness measured in ounces?
In the US, leather thickness isn't weighed. It's measured in ounces. The history is simple: 1 oz is the thickness at which one square foot of leather weighs exactly one ounce. In practice, remember one number: 1 oz = 0.4 mm. Four ounces? Roughly 1.6 mm. Done.
And why is it sold in ranges like "4–5 oz"? Because leather is a natural material. A hide isn't the same thickness everywhere: the back is thicker than the flanks. A 4–5 oz range means the splitting produced 1.6–2.0 mm, and within a single hide you should expect a ±0.2 mm tolerance. Not a defect. Leather.
Measure thickness with callipers at several spots; it tends to be thinner near the edge. If you're measuring with a micrometer, don't press: leather compresses and will read thinner than it really is.
Our catalog stocks leather from 0.8 to 5.2 mm, filtered by exactly the same ranges as this converter: thin, medium, strong and extra strong. Whatever we recommend, we actually have on the shelf.
Frequently asked questions
Exactly 0.396875 mm. In practice, count on 1 oz ≈ 0.4 mm — you won't notice the difference on a finished piece.
7–9 oz (2.8–3.6 mm) for most belts — enough body to hold its shape and take a buckle, while still being easy to skive and stitch.
The recommended thickness depends on the size of the dog:
Small dogs: 5–6 oz (2.0–2.4 mm).
Large dogs: 7–9 oz (2.8–3.6 mm).
Extra-large, powerful breeds (mastiffs, Rottweilers): 9–10 oz (3.6–4.0 mm), or a two-layer construction.
Thickness alone isn't enough, though: at the buckle the leather has to bend, and even a fairly thin strap can crack on the top side unless you skive (thin down) the flesh side at the fold first.
The top-grain layer is the strongest part of the hide, but it still has a limit to how far it stretches. If the flesh side isn't thinned at the fold, the outer surface has to travel a much longer path than the inner side when bent — and it cracks, sometimes just fine surface cracking, sometimes right through.
The fix: skiving the flesh side down to roughly half the original thickness at the fold releases that tension so the bend can flex without damage.
It's the same as “4–5 oz”: a range, not a fraction.
Leather is a natural material and splitting to an exact single weight isn't realistic, so it's sold in ranges instead.
6–8 oz (2.4–3.2 mm) works for most leashes — strong enough for a dog's pull and still comfortable to fold and stitch.