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Letting Out Calculator — Seam Allowance Check
Check seam allowances and calculate letting-out possibilities.
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
You can only let out as much as the existing seam allowance allows. Most ready-to-wear garments have 1-1.5cm seam allowances. You must leave at least 0.5cm seam allowance after letting out for the seam to hold.
Turn the garment inside out and measure from the stitch line to the raw edge. This is the available seam allowance. Check at multiple points as it may vary along the seam.
Options include: adding a gusset (fabric insert) at side seams, adding a panel at centre back, using decorative tape over the seam, or adding side panels. These require additional fabric.
Often yes, especially on dark fabrics. Press with steam and a cloth. For stubborn marks, try a vinegar solution or commercial fabric eraser. Some fabrics (silk, velvet) may show permanent marks.
Related Calculators
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Hem Shortening Calculator
Calculate new hem position and fabric to remove when shortening.
Taking In Calculator
Calculate how much to take in at seams for a smaller fit.
Shoulder Adjustment Calculator
Calculate shoulder width and slope adjustments.
Crotch Depth Calculator
Calculate crotch depth adjustments for trousers.
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Last updated: February 2026
All calculations are estimates. Always verify quantities before cutting or purchasing fabric.