Quilt Block Size Calculator — Cut Size from Finished Size
Enter the finished (sewn-in) size of your block and your seam allowance (0.25″ is the quilting standard). The calculator returns the cut size — the size to cut the piece before sewing — and explains the math.
What this calculator determines
It calculates the cut size of a block from its finished size and seam allowance — cut size equals finished size plus two seam allowances.
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Quilt Size Calculator
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Yardage needed to cut a quantity of same-size pieces from fabric of any width
Sashing Calculator
Sashing fabric yardage from block layout, sashing width, and fabric width
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Border fabric yardage for straight borders, single or multiple
Examples
6″ finished block
6″ finished, 0.25″ seam allowance
Calculation
- Cut size = 6 + 2 × 0.25 = 6 + 0.5 = 6.5″
Cut size 6.5″ × 6.5″
5″ finished, ⅜″ seam
5″ finished, 0.375″ seam allowance
Calculation
- Cut size = 5 + 2 × 0.375 = 5 + 0.75 = 5.75″
Cut size 5.75″ × 5.75″
Assumptions & Conventions
- Seam allowance
- The default seam allowance is ¼″ (the quilting standard) and can be changed to match your pattern.
- One seam per side
- One seam allowance is consumed on each of two opposite edges, so 2 × seam allowance is added per dimension.
- Square blocks
- The calculation is for a square block; for a rectangle, add 2 × seam allowance to each dimension independently.