Sold by area, cut by shape
This is the whole problem in one line. A tannery measures a hide by tracing its outline and reporting the area inside, which is an honest measurement of a piece of leather that happens to be shaped like an animal. Your cutting list is rectangles. The gap between those two facts is the number this page calls the usable share, and it is the only figure on the form that decides whether a job is comfortable or short.
It moves enormously with what you are cutting. Card pockets three inches square will nest into the belly, around a scar, along the neck — almost everything is usable, and people who cut small goods all day report figures near the top of the range. A pair of 44 inch belt straps has to come off the back, in a strip of even thickness and firm temper, running along the backbone. Half a side is simply not eligible for that piece regardless of how good it looks.
So do not carry one number between jobs. The default here is a middling figure for mixed small work, and the moment your list has a long strap in it that figure is optimistic.
The check that is not about area at all
The straight-run test at the bottom of the results catches the failure that square footage cannot see. If your longest piece is 44 inches and the clean run in the hide is 40, no amount of footage saves you. Two hides give you two 40 inch runs, not one 80 inch run.
This is why belt makers buy strips and backs rather than sides. A strip is cut from the back before the hide is split into sides, so it is long, narrow, even in thickness, and priced accordingly. Buying a side because the square footage per dollar looks better, then discovering it will not yield a belt, is a mistake that gets made once.
Thickness, and why it is measured in ounces
Leather thickness is quoted in ounces, where one ounce is one sixty-fourth of an inch. Eight ounce leather is 8/64, or an eighth of an inch. It is called ounces because it once referred to the weight of a square foot at that thickness, and that origin explains nothing useful about the leather in front of you, so treat it as a length unit and move on.
| Weight | Thickness | Where it usually turns up |
|---|---|---|
| 2-3 oz | 0.031-0.047 in | Linings, light bag panels |
| 4-5 oz | 0.063-0.078 in | Wallets, small goods, folded work |
| 6-7 oz | 0.094-0.109 in | Light belts, straps, knife sheaths |
| 8-10 oz | 0.125-0.156 in | Belts, holsters, heavy straps |
A hide is not one thickness across its area. It runs thicker along the back and thinner into the belly, and a tannery that sells leather as 8-9 oz is stating a range because the range is real. If a project needs a consistent thickness across every piece, the usable share drops again, because the belly is out even for pieces that would otherwise nest there.
What this page deliberately does not do
It does not nest your pieces. There is no attempt to lay rectangles onto a shape, because the shape is different on every hide and the decisions are made with a pattern and a marker, not arithmetic. What it gives you is the footage to buy, which is the question you have to answer before the hide arrives.
For rectangular stock where nesting genuinely is arithmetic — plywood, sheet steel, acrylic — the sheet nesting calculator does the real thing with kerf and orientation. For the stitching that follows the cutting, the saddle stitch calculator gives hole counts and thread. If the job is a belt, the belt blank length calculator settles how long the strap has to be before you check it against the run in the hide.
Head knives and round knives are pushed away from the body through material that resists until it suddenly does not. Rotary cutters and strap cutters are worse, because they feel safe.
Questions people ask
What usable share should I put in?
Whatever your own offcut bin says. If you have never measured it: small goods cut from a side, where pieces are a few inches on a side and can be nested anywhere, come out much higher than long straps that can only come from the back. The default of 65% is a middling figure for a mixed list. The way to replace it with something real is to cut one hide for a job you have done before, weigh or trace what you kept against what you bought, and use that ratio next time. It will be specific to your patterns and your tannery, which is exactly what you want.
Why divide by the usable share instead of adding a waste percentage?
Because they are different quantities and the arithmetic differs. A cutting allowance is extra leather consumed by the job — trim between pieces, a strip cut twice — so it multiplies the parts area. The usable share is the fraction of a purchased hide that can be cut at all, so the purchase has to be divided by it. At 65% usable, 1 square foot of parts needs 1.54 square feet of tag footage, not 1.35. Adding 35% instead of dividing by 0.65 leaves you about 12% short here, and short by far more at lower yields. The figure the calculator reports for hide footage per square foot of parts is higher again — 1.69 on the defaults — because it has the 10% cutting allowance in it as well.
Is a side the same as a hide?
A side is half a hide, cut down the backbone, and it is what most suppliers sell to individual makers because a whole hide is unwieldy. A double shoulder, a single bend, a strip and a belly are all smaller cuts taken from specific regions, and they differ in temper and thickness as well as size. Put whatever the supplier lists on the tag into the hide size field, and use the straight-run field to record how long a clean strip that particular cut will actually give you.
Does the calculator account for scars and brands?
Only through the usable share you enter, and that is the honest place for it. Range hides carry barbed wire scars, brands, insect damage and healed cuts, and where they fall is random. A supplier grade tells you roughly how much to expect but not where it lands, so on any single hide you may lose a critical strip or nothing at all. If you are cutting something where a mark is unacceptable, lower the usable share substantially rather than trusting an average.
Can I use this for vegetable tanned and chrome tanned equally?
The arithmetic does not care, but the yields differ in practice. Vegetable tanned leather is generally firmer and more consistent through the back, which suits straps and holsters, while the belly is noticeably softer and often unusable for structural pieces. Chrome tanned garment and upholstery leather is softer throughout and stretches more, so pieces that must hold a dimension have to be cut with the grain direction in mind and the effective yield falls for a different reason. Either way the number to change is the usable share.