Leather Thickness Converterv1.0.0

The same hide gets described three different ways depending on who is selling it. US tanneries quote ounces, most of the rest of the world quotes millimeters, and shoemakers still work in irons. Thickness is usually the first thing you pin down on a project, because it decides how the piece folds, whether it holds a shape, and how much work the edges will take. Temper and tannage matter alongside it: a firm veg-tan and a soft chrome-tan at the same thickness behave nothing alike under a stitching chisel.

Thin and happy to fold. Good for wallet interiors, watch straps, journal covers, light pouches, and garment panels. Seams stay slim, edges finish fast, and topstitching sits flat.

The all-rounder, and where most first projects land. Wallet exteriors, handbags, fashion belts, upholstery panels, and structured cases. Firm enough to take tooling and hold hardware, soft enough to still shape by hand.

Getting stiff. Work aprons, chaps, bag bottoms, saddle seats, moccasins, and holster bodies. Expect to skive anywhere layers overlap, or the seams get bulky quickly.

Belts, holsters, knife sheaths, tack, and heavy straps. Burnishes to a hard edge and keeps its shape under load. Hand stitching at this weight wants a proper awl and harness needles.

1. Pick the unit you have: ounces, millimeters, inches, or irons.
2. Type the thickness: decimals and fractions both work, so 4, 1.6, and 1/16 are all fine.
3. Pick the unit you want: results update as you type, so the Convert button is there only if you would rather click.
4. Read down the panel: the conversion comes first, then the weight class that thickness falls into with the projects and tools that go with it.
5. Come back later: your units and last value stay saved in this browser. Reset clears them.

Conversion reference

• 1 oz ≈ 1/64 in ≈ 0.4 mm
• 1 iron ≈ 1/48 in ≈ 0.53 mm
• 1 in = 25.4 mm

• Wallets and cardholders: check that your lining and your exterior add up to a seam you can actually stitch through.
• Straps and handles: size belts, bag straps, and watch bands so they feel right in the hand and fit the buckle or spring bar you bought.
• Holsters and sheaths: work out welt thickness and total stack before cutting, since retention depends on it.

• Spec sheets: turn a supplier's ounces into the millimeters or irons your own documentation uses.
• Process planning: check thickness against your skiving, stitching, and hardware steps before a run rather than after.
• Sourcing: compare quotes from tanneries that publish in different units without doing the math by hand each time.

• Ounces to millimeters: 5 oz converts to roughly 2.0 mm, a common belt blank thickness before any skiving at the buckle fold.
• Millimeters to ounces: a 1.2 mm lining works out near 3 oz, which is what to ask for when the shop you are buying from quotes in ounces.
• Inches to irons: 1/8 in comes out around 6 irons, the unit shoemakers and some European vendors still quote in.

Is leather thickness the same as weight? No, despite the name. An ounce here is a thickness, roughly 1/64 inch or 0.4 mm. It has nothing to do with what the hide weighs on a scale.

What is an iron? A shoemaking unit, 1/48 of an inch or about 0.53 mm. It shows up most often in sole and welt specs.

Why do I get a range instead of one number? The conversion itself is exact. The range below it is the weight class that value falls into, which is what you order by, since tanneries split to a nominal thickness and real hides drift either side of it.

My measurement sits between two classes. Which do I pick? Go by what the piece has to do. Thinner if it folds, wraps, or turns an edge. Thicker if it carries load or takes abrasion.

Can I enter fractions? Yes. Simple fractions like 1/16 and mixed numbers like 1 1/2 both work, alongside plain decimals.