What Leather Thickness Do You Actually Need? oz to mm, by Project

Most hand sewn leather projects use leather between 2 oz and 10 oz. As a quick rule, wallets want 2 to 4 oz, bags want 4 to 7 oz, belts want 8 to 10 oz, and one ounce equals roughly 0.4 mm of thickness.

That one conversion unlocks every supplier listing you will ever read. Here is how to apply it to your next project.

How leather weight actually works

Leather thickness is sold by weight in ounces. One ounce equals one 64th of an inch, which works out to roughly 0.4 mm, so 4 oz leather is about 1.6 mm thick and 8 oz is about 3.2 mm. Hides are never perfectly even, which is why suppliers sell ranges such as 4 to 5 oz rather than a single number. European tanneries usually list millimetres directly, so keep the 0.4 mm rule in your head and you can shop anywhere.

What each project needs

• Wallets and card holders: 2 to 4 oz (0.8 to 1.6 mm). Use the heavier end for the exterior and the lighter end for the card pockets, or the fold gets bulky fast.

• Bags and backpacks: 4 to 7 oz (1.6 to 2.8 mm). Lighter gives a soft, slouchy bag. Heavier gives structure that stands on its own.

• Belts and straps: 8 to 10 oz (3.2 to 4 mm). Heavy duty belts go up to 12 oz.

• Linings and garment leather: 1 to 2 oz (0.4 to 0.8 mm). Too thin to hold a shape on its own, perfect over a firmer layer.

• Soles and heavy saddlery: 10 to 14 oz (4 to 5.6 mm). Hard work to cut and punch, so keep it for the parts that truly need it.

A worked example from a real pattern

Our Bat Bag crossbody uses two weights in one build: 3.5 square feet of 6 to 7 oz chrome tan for the body and wings, and 1.5 square feet of 4 to 5 oz veg tan for the details. The heavier chrome tan gives the bag its shape while staying soft enough to sew by hand, and the lighter veg tan keeps the layered parts thin enough to stitch through. Every pattern in our shop comes with a materials list like this, so you never have to guess the weight before you buy leather.

If your leather feels wrong

• Wallet too bulky when folded: the exterior is too heavy. Drop to 3 oz or skive the fold line thinner.

• Bag will not hold its shape: go one step heavier, or add a stiffener between the layers.

• Cannot punch through a seam: too many heavy layers stacked. Skive the edges before you stitch.

• Supplier only lists millimetres: divide by 0.4 to get the weight in ounces.

Still not sure? Start small and test a weight on an offcut before you commit to a full hide. Grab something from our free patterns and tools, then find your next build in all patterns.