What is tapering in alterations?

Tapering is gradually changing the seam width along a seam. For example, taking in more at the waist and less at the hip creates a smooth transition. A tapered seam blends naturally into the original seam line.

How do I mark a tapered seam?

Mark the adjustment amount at the start and end points. Connect with a smooth curved line using a curved ruler or French curve. The line should blend gradually — avoid sharp angles which create puckers.

Should I taper from the original seam line?

Always start and end tapering from the original stitch line. At the point where no adjustment is needed, your new stitch line should merge exactly with the old one. Sew a few stitches on the original line before the taper starts.

How long should the taper be?

A general rule is to taper 3-4 times the adjustment amount. If taking in 2cm at the waist, the taper should be at least 6-8cm long. Longer tapers give smoother results.

SewCalcs

Tapering Calculator — Gradual Seam Adjustments

Calculate tapering amounts for gradual seam adjustments.

Start Point Reduction

Total reduction at starting point

End Point Reduction

Total reduction at ending point

Seam Length

Length of tapered section

Number of Seams

How We Calculate This

Tapering calculations show the seam adjustment at the start and end points, distributed across seams. The taper rate shows how quickly the adjustment changes per centimetre of seam.

The formula

Per side at start = Start reduction ÷ Seams ÷ 2

Per side at end = End reduction ÷ Seams ÷ 2

Taper rate = (End - Start) per side ÷ Seam length

Frequently Asked Questions

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Last updated: February 2026

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