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Imperial to Metric Conversion Guide

Date Posted:17 July 2022 

Don’t you just hate having to convert pattern and design directions from imperial to metric, and vice versa? 
Don’t worry, we at Echidna have made it easy! We’ve created a handy print-out chart of the most common sewing and quilting size conversions for you to refer to. 

Seam Allowances

The term “seam allowance” refers to the area between the stitching and the raw edge of the fabric. Most patterns call for a specific size allowance. Without it, your fabric pieces may not line up correctly, or you may find you don’t have enough fabric. 

¼" 6mm
⅜" 10mm
½" 12mm
⅝" 16mm
¾" 19mm
seam allowance examples

Pre-Cut Fabric Sizes

You’ve heard of “Fat Quarters”, just one example of pre-cut fabric, but what size is it? Pre-cut fabric comes in all different shapes and sizes depending on the requirements of your project.

Fat Quarter (AU) 19" x 21" 50cm x 55cm
Fat Quarter (USA) 18" x 22" 45cm x 55cm
Fat Eighth 9" x 22" 22.5cm x 55cm
Layer Cakes 10" x 10" 25.4cm x 25.4cm
Jelly Roll 2.5" x 44" 6.35cm x 112cm
Charm 5" x 5" 12.75cm x 12.75cm
Pre-cut fabric sizes

Inches to Millimeters/Centimeter

⅛" 3mm
¼" 6mm
⅓" 8mm
⅜" 10mm
½" 12mm
⅝" 16mm
⅔" 17mm
¾" 19mm
1" 2.5cm
1¼" 3.2cm
1½" 3.8cm
1¾" 4.4cm
2" 5.1cm
2¼" 5.7cm
2½" 6.4cm
2¾" 7.0cm
3" 7.6cm
3¼" 8.25cm
3½" 8.9cm
4" 10.2cm
4½" 11.4cm
5" 12.7cm
5½" 14cm
6" 15.2cm
7" 17.8cm
8" 20.3cm
9" 22.9cm
10" 25.4cm
11" 28cm
12" 30.5cm

Yards to Centimeter

⅛ yard 11.4cm
¼ yard 22.9cm
⅓ yard 30.5cm
⅜ yard 34.3cm
½ yard 45.7cm
⅝ yard 57.2cm
⅔ yard 61cm
¾ yard 68.6cm
1 yard 91.4cm
1¼ yard 114.3cm
1½ yard 137.2cm
1¾ yard 160cm
2 yards 182.9cm
2¼ yards 205.7cm
2½ yards 228.6cm
2¾ yards 251.5cm
3 yards 274.3cm
3½ yards 320cm
4 yards 365.8cm