Free tool
Stitch hole spacing calculator
Type the length of your seam and choose your pricking iron. The calculator works out how many stitching holes fit, the exact spacing, and how many presses of the iron it takes. It uses the same rules as PatinaCAD.
Why the holes don't come out even
A seam is rarely a whole number of iron spacings. A 200 mm seam with a 3.85 mm iron is 51.9 spacings long. Walk the iron along it and you end with a 3.65 mm gap where a full stitch should be, or a hole squeezed in at the end. On a wallet or a card holder that odd stitch often lands on a corner, where it shows most.
There are three ways to deal with it. The calculator does all three, so you can compare them before you pick up the iron.
Three ways to space the holes
Fixed spacing
Every stitch is exactly your iron's spacing. At the open end of a seam the holes stop at the last whole spacing, and the length left over gets no hole. That suits two edges that will be sewn together: start both at the same point and the holes match one for one.
Before a corner, a hole goes right on the corner. The odd length is shared over the last few stitches, so none of them is more than 10% longer or shorter than the iron's spacing, as long as the side has room. On a 40 mm side with a 3.85 mm iron, the last four stitches become 4.225 mm.
Adjusted spacing
The spacing closest to your iron's that fits each side exactly, with a hole at both ends. Divide the length by the iron's spacing, round to the nearest whole number of stitches (a half rounds up), then divide the length by that number. A 200 mm seam with a 3.85 mm iron gets 52 stitches of 3.846 mm: 0.004 mm less than the iron, far too little to see.
A set number of holes
Exactly the number of holes you ask for, evenly spaced. The spacing is the length divided by one less than the number of holes: 50 holes on 200 mm are 4.082 mm apart. Use it when two pieces of different length must carry the same number of holes, such as a panel and its gusset.
A hole on every corner
For a pocket or a card holder, type the length of each side separated by commas: 40, 85.6, 40 for a pocket stitched down one side, along the bottom and up the other. Each side is worked out on its own and a hole lands on every corner, so the thread turns the corner cleanly. When the stitching goes all the way round, such as on a coaster or a patch, tick “The sides go all the way round”.
Measure each side along the stitch line, from corner to corner. The stitch line sits a few millimetres in from the cut edge, so it is shorter than the edge: with the line 3.5 mm in, a 96 mm wide panel has an 89 mm stitch line along the bottom.
Reading the result
- Holes counts every hole in the seam, with each corner hole counted once. A seam has one stitch fewer than it has holes, or the same number when it goes all the way round.
- Spacing is the distance between neighbouring holes, centre to centre, and how far it is from your iron's. With several sides, the table shows each side.
- Left at the end is the length after the last hole with fixed spacing. Trim it off, start the seam a little further along, or switch to adjusted spacing.
- Presses is how many times you strike the iron. After the first press the first prong goes back into the last hole, so each press adds one hole fewer than the iron has prongs. Each side starts again at its corner.
Print the hole strip
The strip under the result shows every hole at actual size, with the corners marked. Print it at 100% (“Actual size” in the print dialog) and check the 100 mm line with a steel rule. Cut the rows out, lay them along the stitch line, and mark each hole with an awl or set the iron's prongs on the marks. If the line doesn't measure 100 mm, the printer scale test page shows how to correct it.
Tips
- Choose the spacing before you cut. Smaller spacing suits thin leather and fine thread; the pricking iron size chart lists common sizes in mm and stitches per inch.
- Use the same iron and the same mode for pieces that are sewn together, and start both from the same corner.
- The calculator works on straight sides. For rounded corners and curves, PatinaCAD measures the stitch line for you and spaces the holes along the curve.
Related pages
Free to use
Do it automatically in PatinaCAD.
PatinaCAD lays out the holes with these same rules as you click along the stitch line, on straight sides and curves, then prints the pattern at actual size.