What is a welt pocket?

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.

How wide should a welt be?

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.

Do I need interfacing?

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.

SewCalcs

Welt Pocket Calculator — Single & Double Welt

Calculate dimensions for single welt and double welt pockets including pocket bag and interfacing.

Pocket Opening Width

Finished opening — typically 12–15cm jacket breast, 13–16cm hip

Welt Height

Finished height of each welt lip, usually 0.6–1cm

Pocket Depth

Finished depth of the pocket bag, around 15–18cm

Pocket TypeDouble welt = two lips (jetted/besom); single = one lip

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

Related Calculators

Seam Allowance Calculator

Calculate seam allowance amounts and adjust pattern pieces accordingly.

Seam Allowance Fabric Calculator

Calculate total fabric needed for multiple pattern pieces with seam allowances added to every edge, including waste percentage and cutting layout.

Dart Calculator

Calculate dart dimensions for shaping bodices, skirts and trousers.

Pleat Calculator

Work out fabric needed for box pleats, knife pleats and inverted pleats.

Gather Calculator

Calculate fabric width needed for gathered sections based on fullness ratio.

Last updated: February 2026

All calculations are estimates. Always verify quantities before cutting or purchasing fabric.