Calculate pattern piece sizes with seam allowance adjustments for garments and quilts.
Every edge of a pattern piece that will be stitched to another needs extra fabric between the stitching line and the cut edge. That extra width is the seam allowance, and this tool does the addition for you: enter the finished size of a piece and the allowance you sew with, and it returns the dimensions to cut. The move that trips most people is adding the allowance once instead of twice, because every seam has two edges. At the garment standard of 5/8 in, a 10 in finished panel needs 11 1/4 in cut, not 10 5/8 in. The same math holds for quilting's 1/4 in.
A concrete input and expected output from the current implementation.
Input
Finished size: 10 in x 12 in, seam allowance: 5/8 in
Expected output
Cut size: 11 1/4 in x 13 1/4 in
Each dimension carries two seams, so the allowance is doubled before adding: 5/8 in x 2 = 1 1/4 in. The 10 in side becomes 11 1/4 in and the 12 in side becomes 13 1/4 in.
Seam allowance is a per-edge value: a rectangle has two seams on each dimension, so the calculator doubles the allowance before it touches the finished size. A 10 in side at 5/8 in gains 1 1/4 in total, never 5/8 in. The number you enter must be the single-edge width, the distance from the stitching line to the cut edge.
The finished size is where the stitching lands, not the outer edge of a printed pattern. Commercial tissue already carries a built-in allowance, so its outer edge is a cut size and its seam line is the finished size. For a pattern with no allowance, the pattern dimension is the finished size and the calculator's answer becomes your cutting line. Entering the wrong one shifts every seam by the full allowance.
No. The pattern's outer edge is the cut size; the stitching line is the finished size. Enter the seam-line measurement, not the outer edge. Entering the outer edge as the finished size adds another 1 1/4 in per dimension, and the garment comes out too big. Only add allowance when the pattern genuinely has none.
That is a convention, not something the calculator decides: 5/8 in is the US garment standard, 1/4 in is the quilting standard, European patterns often use 1 cm, and knit or indie PDF patterns frequently call for 3/8 in. Use what the pattern specifies; the tool only adds the number you give it.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
Create customizable checklists with groups, due dates, and priorities for any project.
Design a printable daily planner with time blocks, goals, and priority sections.
Measure your typing speed in WPM and accuracy with real-time feedback and stats.
Pomodoro timer with built-in ambient noise (rain, cafe, forest) generated via Web Audio API oscillators.
Stay focused with a customizable Pomodoro timer featuring work and break intervals.
A precise stopwatch with lap tracking, split times, and exportable results.