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Welt Pocket Calculator — Single & Double Welt
Calculate dimensions for single welt and double welt pockets including pocket bag and interfacing.
How We Calculate This
Welt pocket pieces are calculated from the finished pocket opening plus the handling and seam allowances each construction step needs.
Cutting dimensions
- Welt strip: opening width + 5cm (2.5cm spare each end to wrap the corners) × welt height × 4 (the strip folds to frame the lip). Cut 2 strips for a double welt, 1 for a single.
- Pocket bag: opening width + 2 × seam allowance, by twice the finished depth + 2 × seam allowance (the bag folds at its base).
- Interfacing patch: opening width + 4cm × welt extent + 4cm — 2cm spare on every side to stabilise the opening.
Welt-strip rule follows the Itch to Stitch and So Sew Easy double-welt tutorials (strip cut ≈5cm longer than the opening and four times the finished welt width). The seam allowance defaults to the UK garment standard of 1.5cm (⅝in) and is adjustable under Advanced options.
Frequently Asked Questions
A welt pocket has a narrow fabric lip (welt) that covers the pocket opening. A single welt has one lip; a double welt (also called a jetted or besom pocket) has two lips that meet in the middle. They are common on tailored jackets and trousers.
Standard welt height is 0.6–1cm for each lip. The pocket opening width is typically 12–15cm for jacket breast pockets and 13–16cm for hip pockets.
Yes, always interface the garment fabric behind the welt opening. This stabilises the area and prevents stretching. Cut the interfacing piece 2cm larger than the pocket opening on all sides.
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Last updated: February 2026
All calculations are estimates. Always verify quantities before cutting or purchasing fabric.