Choosing leather for a watch strap

The strap is stiff as a board and won't bend round the spring bar. Or it bends fine, then cracks or stretches a month later. The wrong leather can make a strap harder to make, or mean it doesn't last as long as hoped. Two choices matter: how thick it is, and how it was tanned.

Start with thickness

Leather thickness is measured in ounces in the US and in millimeters in most other countries¹. The word is confusing, because an ounce here has nothing to do with how heavy the leather feels. In leathercraft, an ounce is a measurement of thickness¹.

So what does that mean in millimeters? A 4 oz piece is about 1/16 inch, or 1.6 mm, thick¹.

Tandy lists thin leathers of 1 to 3 oz as great for lining, watch straps and wallet interiors¹. That's the range to shop in. The same page warns that when leather is too thick, it might be hard to sew or fold¹. A watch strap does both, in a very small space.

Lined straps add up

If you plan to glue a lining under the outer leather, think about the two layers together. The source says that for items with multiple layers, the combined thickness matters as much as the individual layer¹. One maker's watch strap tutorial glues a liner to the outer leather to make a continuous strip². A thin liner and a thin outer can still add up to something thick at the fold. Check the pair, not each piece alone.

Full-grain or top-grain

Grain describes the outer surface of the hide. Tandy describes full-grain leather as strong and durable, one that develops a patina over time³. Top-grain is slightly sanded and finished for a more uniform look³.

The source doesn't rank one above the other for watch straps. How the leather was tanned tells you more about how it will bend, and the next section covers that.

Tanning: firm or soft

Tanning is the treatment that turns raw hide into leather. Tandy's guide separates the main types.

Think about the trouble you're trying to avoid. If a strap feels like a plank, a softer leather may help. If you want a strap that holds a firm shape, vegetable-tanned leather may suit. The table doesn't tell you which one lasts longer on a wrist, so I won't claim that.

A word on exotic leathers

Shell cordovan comes up in strap tutorials. It's one of the most expensive leathers in the world². That price alone is a reason to leave it until you've made a strap or two from something cheaper.

Buying for a small project

You don't need a whole hide. Tandy says that for small projects like wallets or watch straps, pre-cuts are easier and cheaper³. A pre-cut piece also lets you try a thickness without committing to a big purchase.

Whatever you buy, the wrong type can make the project harder to make, or mean it doesn't last as long as you'd hoped³. Once you've picked, gather your tools.