SewnCake Sewing Tool
Seam Allowance Converter
No more wondering what ⅜" is in millimeters. Tap a common sewing fraction or enter any custom measurement and get the conversion instantly.
Quick convert
Common seam allowances
9.5 mm
⅜" = 0.375" = 9.525 mm = 0.953 cm
Custom measurement
9.525 mm
0.953 cm · ⅜"
SewnCake tip: Sewing patterns often round metric equivalents for convenience. For example, ⅜" is exactly 9.525 mm, but you’ll often see it written as 10 mm.
Quick sewing reference
| Inches | Decimal | Millimeters | Centimeters |
|---|---|---|---|
| ⅛" | 0.125" | 3.175 mm | 0.318 cm |
| ¼" | 0.250" | 6.350 mm | 0.635 cm |
| ⅜" | 0.375" | 9.525 mm | 0.953 cm |
| ½" | 0.500" | 12.700 mm | 1.270 cm |
| ⅝" | 0.625" | 15.875 mm | 1.588 cm |
| ¾" | 0.750" | 19.050 mm | 1.905 cm |
| ⅞" | 0.875" | 22.225 mm | 2.223 cm |
| 1" | 1.000" | 25.400 mm | 2.540 cm |
Exact conversions are shown above. Your pattern instructions may use rounded metric values.