Letting Out Calculator — Seam Allowance Check
Check seam allowances and calculate letting-out possibilities.
Enter the current measurement
Enter the desired measurement
Measure inside the garment
Seam allowance measurement
How We Calculate This
The calculator checks whether your seam allowance is sufficient to let out the garment by the desired amount. A minimum of 0.5cm seam allowance must remain.
The formula
Total increase = Desired - Current measurement
Per side = Total increase ÷ Seams ÷ 2
New seam allowance = Original SA - Per side
Possible if new SA ≥ 0.5cm
Frequently Asked Questions
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Last updated: February 2026
All calculations are estimates. Always verify quantities before cutting or purchasing fabric.