Stitch spacing calculator for leather
Enter the length of the seam and the spacing of your chisel, pricking iron or wheel. You get the number of holes, whether the last hole lands on the corner, and the small adjustment that makes it land there. Works in millimetres or stitches per inch.
Doing this on a whole pattern? EasyPatt places the holes for you on every edge, shows the count per side, and prints the pattern to scale — free, in your browser.
How the calculator works
The number of gaps between holes is the seam length divided by the spacing. A 120 mm seam at 4 mm gives 30 gaps and 31 holes, and the last hole lands exactly on the corner. Most seams are not that tidy. At 125 mm you get 31.25 gaps, and you have to choose.
Land on both corners (balancing)
Round the gaps to a whole number, 31, and divide the length by it: 4.03 mm per stitch. The difference from 4 mm is invisible, and the seam starts and ends on a hole. This is the default here and in EasyPatt, and it is the right choice for anything with visible corners: wallets, card holders, bag flaps.
Keep exact spacing (walking)
Keep 4 mm exactly, get 31 gaps, and leave the 1 mm remainder at the end. This matches what a pricking iron does when you walk it along an edge from one corner. Fine for a long edge whose end is hidden or trimmed later, or when the remainder is under a third of the spacing.
With irons, the practical trick for balancing is to mark from both corners toward the middle, so the adjustment ends up mid-seam where nobody looks. Read more in the saddle stitch spacing guide.
SPI to mm conversion
Stitches per inch is the American convention; millimetres the European one. The conversion is 25.4 ÷ SPI.
| SPI | Spacing | Typical use |
|---|---|---|
| 4 | 6.35 mm | Heavy belts, holsters |
| 5 | 5.08 mm | Belts, heavy bags |
| 6 | 4.23 mm | Bags, sheaths |
| 7 | 3.63 mm | Wallets, straps |
| 8 | 3.18 mm | Fine wallets, watch straps |
| 9 | 2.82 mm | Thin lining leather |
| 10 | 2.54 mm | Very fine work |
Chisels sold in millimetres rarely match a whole SPI: a 3.38 mm chisel is 7.5 SPI, a 3.85 mm chisel is 6.6 SPI. Type the number on the chisel into the calculator and it shows the SPI.
Charts for common spacings
Each page has the calculator pre-set to that spacing and a hole chart for common seam lengths.
2.7 mm 3 mm 3.38 mm 3.85 mm 4 mm 5 mm 6 mm 4 SPI 5 SPI 6 SPI 7 SPI 8 SPI 9 SPI 10 SPI
Common questions
How do I convert stitches per inch to millimetres?
Divide 25.4 by the SPI. 8 SPI is 25.4 ÷ 8 = 3.18 mm between holes; 6 SPI is 4.23 mm. To go the other way, divide 25.4 by the spacing in millimetres: a 4 mm chisel is 6.35 SPI.
How many stitch holes fit on my seam?
Divide the seam length by the spacing and add one for the hole at the start. A 100 mm seam at 4 mm has 25 gaps, so 26 holes. If the length is not an exact multiple, either keep the exact spacing and accept a short gap at the end (walking), or stretch or squeeze the spacing a little so a hole lands on both ends (balancing).
How do I make stitch holes land exactly on the corners?
Round the number of gaps to a whole number and divide the seam length by it. A 101 mm seam at 4 mm has 25 gaps of 4.04 mm; nobody can see the 0.04 mm, but the last hole sits exactly on the corner. This is what the Balancing option does. With pricking irons, mark the seam from both corners toward the middle so the small difference ends up mid-seam.
What stitch spacing should I use for leather?
Thicker leather takes wider spacing. Roughly: 2.5 to 3 mm (8 to 9 SPI) for thin lining leather, 3 to 4 mm (6 to 8 SPI) for wallets and watch straps, 4 to 5 mm (5 to 6 SPI) for small bags and sheaths, 5 to 6 mm (4 to 5 SPI) for belts and heavy bags.
The calculator uses the same code that places stitch holes in the EasyPatt editor, so the numbers here match what you will see on a printed pattern.