Converter
Leather thickness converter, ounces to millimetres.
Leather is sold by weight in ounces, measured in millimetres and described in irons. Convert between all three and see what each thickness is used for.
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What each weight is for
| Weight | Thickness | Typical uses |
|---|---|---|
| 1 to 2 oz | 0.4 to 0.8 mm | Linings, bookbinding leather, the inside of a wallet |
| 2 to 3 oz | 0.8 to 1.2 mm | Wallet interiors, card slots, watch strap linings, light pouches |
| 3 to 4 oz | 1.2 to 1.6 mm | Wallets, cardholders, journal covers, small bags |
| 4 to 5 oz | 1.6 to 2.0 mm | Bags and totes, notebook covers, light straps, moccasins |
| 5 to 6 oz | 2.0 to 2.4 mm | Lighter belts, bag bodies, knife sheaths with a welt |
| 6 to 7 oz | 2.4 to 2.8 mm | Belts, straps, dog collars, guitar straps |
| 7 to 8 oz | 2.8 to 3.2 mm | Heavy belts, light holsters, carved and tooled pieces |
| 8 to 9 oz | 3.2 to 3.6 mm | Holsters, sheaths, heavy straps, armor pieces |
| 9 to 10 oz | 3.6 to 4.0 mm | Holsters, saddle parts, heavy tooling |
| 10 to 12 oz | 4.0 to 4.8 mm | Saddle skirting, heavy sheaths, shoe soles |
| 12 oz and up | 4.8 to 4.8+ mm | Soles, saddle trees, armor |
That is
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Millimetres-
Inches-
Irons-
Used for-
One ounce of leather weight is 1/64 of an inch, about 0.4 mm. A hide is never perfectly even, so leather is sold in a range, 5 to 6 oz, and a piece from it measures anywhere between.
Why leather is sold in ounces
Leather weight is an old trade measure: a square foot of leather one ounce in weight is about 1/64 inch thick, and the thickness kept the name. So oz × 0.397 = mm and oz / 64 = inches. A 5 oz hide is about 2 mm; an 8 oz hide, 3.2 mm. Because hides vary across their surface, suppliers quote a range, and the piece you cut may be at either end of it.
Soling leather and some European suppliers use irons, 1/48 inch each, so a 9 iron sole is a little under 5 mm. Many sellers now simply quote millimetres.
Choosing a weight
- Thinner is easier to cut and stitch and harder to make look good; thick leather forgives a wobbling knife and rewards a crisp edge.
- A first project in 4 to 5 oz vegetable-tanned leather, a cardholder or a simple belt pouch, teaches cutting, edging and the saddle stitch without the fight of 9 oz.
- Belts are the classic 8 to 9 oz project; the saddle stitch calculator tells you how much thread a belt keeper or a strap needs.
- Two thin layers glued and stitched behave like one thicker piece; bag makers build up weight this way for a lining and a face.
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