🧵 Stitching Spacing Calculator
Enter your total seam length and desired stitch spacing (matching your pricking iron or overstitch wheel) to see how many stitches you'll need.
Seam length divided by the pitch of your iron
The count is one division, rounded to the nearest whole stitch:
stitches = round(seam length / stitch spacing)
400 mm / 4 mm = 100 stitches
holes on an open seam = stitches + 1 = 101What comes back is the number of 4 mm steps along the seam, so punching from one end you will make 101 holes: the first one, then 100 more. On a closed loop, a bracelet or a bag gusset that meets itself, holes and stitches are equal. Rounding means a seam that does not divide evenly is absorbed: 400 mm at 3.85 mm returns 104 stitches, which really sit at 3.846 mm apart.
Matching pitch to the project
| Pitch | Stitches per inch | Suits |
|---|---|---|
| 2.0 mm | 12.7 | Watch straps, fine card cases |
| 2.7 mm | 9.4 | Wallets, small goods |
| 3.0 mm | 8.5 | Wallets, light bags |
| 3.85 mm | 6.6 | Bags, belts, sheaths |
| 4.5 mm | 5.6 | Heavy straps, tack, saddlery |
Irons are sold either way, and the two scales convert with
SPI = 25.4 / pitch in mm. Coarser pitch suits thicker leather: a
2.7 mm stitch on an 8 oz belt reads as a perforation, while 4.5 mm on a wallet
looks agricultural. Whatever you choose, the thread has to fill the hole, so a
3 mm pitch wants 0.45 mm thread and 3.85 mm wants 0.6 mm.
Frequently asked questions
How many stitches per inch is a 4 mm pricking iron?
6.35, which makers round to 6 SPI. Divide 25.4 by the millimetre pitch to convert any iron.
What stitch spacing should I use for a leather wallet?
2.7 to 3.0 mm. It keeps the stitch line in proportion on 2–4 oz leather and still leaves room for 0.45 mm thread to seat without cutting the grain.
Do I count the last hole as a stitch?
No. The figure here is the gaps between holes, so an open seam needs one more hole than the stitch count. Cast off at the last hole and back-stitch two.