Leather thickness for shoe uppers: what to spec in mm
Every shoemaking blog gives you a number. No blog tells you that a tannery sells a range, that the range has a tolerance, or that the belly of the hide will not hold it. Here is how substance is actually specified and bought.
A guide by TL San Martín, a tannery of origin in Elda (Alicante, Spain) since 1995, LWG Gold certified under the Leather Manufacturer standard.
Upper leather for footwear runs between 1.0 and 2.2 mm, and you never order a single number — you order a range, called the substance: 1.2–1.4 mm, 1.4–1.6 mm, 1.6–1.8 mm. Sneakers sit at the thin end, unlined boots at the thick end, and linings are a separate order at 0.6–1.0 mm. Getting this wrong is the most expensive cheap mistake in a first collection.
Why does the tannery quote a range instead of a thickness?
Because a hide is not a sheet of plastic. Thickness is not uniform across one animal, and it is not identical between two animals in the same lot.
A hide is thickest and tightest on the butt (the back and rump), thinner and looser on the belly and flanks, and thinner again on the neck, where the fibre is also more open. When we split and shave a hide to 1.4–1.6 mm, that range is what the usable cutting area holds. The belly will not hold it the same way — which is exactly why your factory's cutting plan discards it or sends it to non-visible parts. That is a normal feature of the material, not a defect, and it is covered in defect or normal factory flaw.
Two things follow:
- A tolerance of about ±0.1 mm inside the batch is normal and industry-standard. If a supplier promises you an exact 1.5 mm with no range, they are either not measuring or not making the leather.
- Thickness is measured to a standard, not by eye: ISO 2589 (leather — physical and mechanical tests — determination of thickness), with a gauge at a defined pressure. Ask where on the hide the measurement was taken. "1.6 mm" measured on the butt and "1.6 mm" as a lot average are two different pieces of leather.
What thickness for which shoe?
| Construction | Upper substance | Why |
|---|---|---|
| Sneaker / trainer, lined | 1.0–1.2 mm | Must fold cleanly over a soft last and take stitching through several layers without bulk |
| Dress shoe / derby / loafer, lined | 1.2–1.4 mm | Classic calf range. Body enough to hold the last, thin enough for a clean edge and folded seams |
| Goodyear-welted shoe | 1.4–1.6 mm | Has to survive lasting tension and, eventually, being re-lasted at resoling |
| Boot, lined | 1.6–1.8 mm | Shaft needs standing body; the toe area takes the abuse |
| Unlined boot / work boot | 1.8–2.2 mm | The upper is also the lining — it must be comfortable directly against the foot |
| Sandal upper (unlined strap) | 1.8–2.2 mm | Nothing behind it; a thinner edge would curl |
| Barefoot / minimalist, lined | 1.0–1.4 mm | Flexibility is the product. See leather for barefoot shoes |
| Lining (goat, sheep) | 0.6–0.8 mm | Must not steal volume inside the shoe |
| Lining (veg calf, welted) | 1.0–1.2 mm | Firmer footbed side, moulds to the foot |
Two zones of the same shoe can carry different substances. It is common to spec the vamp and quarters at 1.4–1.6 mm and the tongue or a folded collar thinner, because a folded edge has to skive down to almost nothing. Tell the factory at pattern stage, not after the first prototype comes back bulky at the collar.
How do you convert ounces to millimetres without getting burned?
If your reference is American — and most online shoemaking content is — the spec arrives in ounces. This trips up almost every founder once.
1 oz = 1/64 inch ≈ 0.4 mm.
| Ounces | Millimetres | Typical use |
|---|---|---|
| 2–3 oz | 0.8–1.2 mm | Lining |
| 3–4 oz | 1.2–1.6 mm | Dress shoe and sneaker upper |
| 4–5 oz | 1.6–2.0 mm | Boot upper |
| 5–6 oz | 2.0–2.4 mm | Unlined or heavy boot, sandal strap |
The trap: ounces are a weight per unit area converted to thickness by convention, and suppliers round them differently. "5 oz" from one source is 1.8 mm and from another 2.0 mm. When you place a real order, write the millimetre range. Nobody in a European tannery cuts to ounces.
Does a thicker upper cost more?
Not the way founders expect, and this is the part the rest of the internet gets wrong.
Leather is sold by area — square feet or square metres — not by weight. Going from 1.2–1.4 mm to 1.6–1.8 mm does not, on its own, change the price per square foot at most tanneries. What it changes is this:
- The raw selection. A heavier substance has to come off a heavier raw hide. That can move you into a different raw price band, and it usually reduces how many hides in a lot can serve your article at all.
- The yield of the split. A thick upper leaves less usable split underneath; a thin one leaves more. That economics sits with the tannery, but it shows up in which articles are offered in which substances.
- Your consumption per pair. Not because of the millimetres, but because thicker leather is less forgiving in the cutting plan: it tolerates less stretch correction, so pieces must be placed more strictly with the direction of stretch. Run the numbers in how much leather you need for a pair of shoes, and the price side in leather price per square foot.
- Your factory's time. Thicker uppers are harder to last and harder to skive. Some factories quote a higher making charge above 1.8 mm.
So the honest answer: specify the thickness the shoe needs. Trying to save money by dropping 0.2 mm below what the construction wants buys you a shoe that breaks at the vamp crease in month three.
The failure you are actually trying to avoid
Under-specced upper leather on a roomy last is the classic first-collection failure. The leather is too thin to hold the volume the last created, so after a few weeks of wear the vamp develops deep, sharp creases instead of soft ones, the quarters collapse inward around the heel, and the shoe looks two years old. It is not a leather quality problem — it is a substance specification problem, and it cannot be fixed after production.
The reverse exists too and is cheaper to spot: too thick, and the shoe will not last cleanly, the toe puckers, and folded edges stay chunky no matter how well they are skived.
This is why substance goes on the technical sheet before the first prototype, and why you should request samples in two adjacent substances and have your factory last both. Two prototypes cost less than one wrong production run.
For the Spanish-language version of this decision across products beyond footwear — bags, belts, small leather goods — see espesor del cuero para tu producto. For every other material decision in a first collection, our hub: leather for shoes. And if you have not yet chosen a tanning route, that decision is in chrome-free leather for shoe brands.
Frequently asked questions
What thickness should I ask for if I don't know my construction yet?
Don't ask yet. Decide lined or unlined and pick your last first — those two choices set the substance. If you need a placeholder for a first sampling round, 1.4–1.6 mm covers the widest range of lined footwear.
Can the same article be supplied in different substances?
Usually yes, within limits. A given article is developed around a raw selection and a finish, and stretching it to a much heavier substance may not be possible from the same hides. Ask the tannery which substances that specific article is made in before you design around it.
Why did my second order feel different at the same millimetres?
Substance is not the same as firmness. Two leathers at 1.4–1.6 mm can feel completely different depending on tannage, fatliquor and finish. If handle matters — and for an upper it always does — approve a physical production reference, not just a number.
Does thickness change after finishing?
Slightly. Shaving sets the substance; finishing adds a few hundredths of a millimetre depending on the coating. The tannery's quoted range refers to the finished leather you receive, which is what you should be measuring on arrival.
Need a specific substance in a batch size you can absorb? Thin uppers and heavy unlined substances are the two ends nobody keeps in stock in every colour. The TL San Martín Business Board is our free, open B2B board for leather and footwear. Post under Materials with the article type, the substance range in mm, the colour and the quantity — tanneries and other brands read it, and a batch you can share is often one post away. If your problem is finding a factory that lasts heavy unlined uppers, post under Partners & factories instead.
TL San Martín tans and finishes leather in Elda, Alicante, since 1995: LWG Gold under the Leather Manufacturer standard — the only standard under which a Gold medal exists at all; a Trader tops out at "Approved". Request samples in the substance you intend to buy.