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Shoulder Adjustment Calculator — Width & Slope
Calculate shoulder width and slope adjustments.
How We Calculate This
Across-back width spans both shoulder seams, so the total change is divided equally between them — each bodice piece (cut on the fold) takes half. Width is moved at the armhole end of the shoulder seam; slope raises or lowers the shoulder point at that same end.
A width move kept under about 2 cm per shoulder reshapes only to the armhole seamline, leaving the armscye length — and the sleeve — unchanged. The slope change is what alters armscye height, so the indicative sleeve-cap figure keys off the slope adjustment; lower (or raise) the armhole by the same amount to keep the armscye length, then re-true the sleeve cap.
The formula
Width adjustment = Desired - Current width
Per shoulder = Width adjustment ÷ 2
Slope adjustment = Desired slope - Current slope
Sleeve cap (indicative) = |Slope adjustment| × factor
Frequently Asked Questions
The shoulder seam should sit at the point of your shoulder (the bony bump). If the seam sits on your arm, the shoulders are too wide. If it digs into the top of your arm, they are too narrow.
Shoulder slope is adjusted at the armhole end of the shoulder seam. For sloping shoulders, lower the shoulder point. For square shoulders, raise it. This also affects the armhole and may need a corresponding sleeve adjustment.
Yes, by taking a deeper seam at the shoulder point and tapering to nothing at the neckline. This narrows the shoulder while maintaining the neckline position. You may need to adjust the sleeve head to match.
Changing the shoulder width or slope changes the armhole shape and size. The sleeve cap may need adjusting to fit the new armhole. Check the sleeve ease (usually 2-4cm) after adjusting the bodice shoulders.
Related Calculators
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Crotch Depth Calculator
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Armscye Calculator
Calculate armscye (armhole) circumference and adjustments.
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.
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Last updated: February 2026
All calculations are estimates. Always verify quantities before cutting or purchasing fabric.