Metric and imperial quilt conversions
Updated 2026-07-06
The two numbers to remember: 1 inch is exactly 2.54 cm, and 1 yard is exactly 0.9144 m. To convert, you multiply. Inches times 2.54 gives centimeters; yards times 0.9144 gives meters. The one rule that saves you from cut mistakes is to never mix the two systems inside a single measurement. Pick one unit for a project and stay in it from the first cut to the last seam.
Why are quilting patterns usually in inches?
Most modern quilting grew up in the United States, so the pattern world, the rulers, and the rotary mats are built around inches. Fabric comes off the bolt at a width measured in inches, block sizes are quoted in inches, and seam allowances are written as fractions of an inch. If you quilt outside the US, you will still meet imperial patterns constantly, which is exactly why a clean conversion habit matters.
The conversion table you actually need
Here are the measurements that come up most often, converted once so you do not have to.
| Imperial | Metric | Notes |
|---|---|---|
| 1/4“ | 0.635 cm (about 6 mm) | The standard seam allowance |
| 1/2“ | 1.27 cm | Common for bags and heavier seams |
| 2.5“ | 6.35 cm | A jelly roll strip and a typical binding strip |
| 42“ (WOF) | 106.7 cm | Usable width off the bolt, before trimming selvages |
| 1 yard | 91.44 cm (0.9144 m) | The fabric-store unit |
Keep this near your cutting mat. If a pattern gives you inches and your ruler is metric, convert the whole cut list at the start, not one piece at a time.
Is a 1/4 inch seam really 6 mm?
Close, but not exact. A quarter inch is 6.35 mm, so 6 mm is a hair narrow and 7 mm is a hair wide. That gap sounds tiny, and on one seam it is. Across a block with a dozen seams it adds up, and a block that should finish at 12 inches can land a quarter inch small. If your pattern was written in inches, sew the imperial seam. If you have committed to metric, pick 6 mm or 7 mm and use it everywhere so the error is consistent instead of random.
How should I round metric cutting measurements?
Round to the nearest millimeter, and round consistently in one direction when a number lands between two marks. Cutting slightly generous is safer than cutting short, because you can trim a block down but you cannot add fabric back. For yardage, round up to a friendly amount at the shop. A conversion that gives you 2.74 m is fine to buy as 2.8 m or even 3 m if you want insurance for squaring up.
One thing not to do: convert an imperial cut to metric, round it, then convert back to imperial later. Every round trip nudges the number, and after a few passes your pieces no longer match. Convert once, at the start, and then live in that unit.
How Sashing handles it
Sashing keeps a whole project in one unit. You choose inches or centimeters, and every result, from the quilt backing calculator to your cut lists, comes back in that unit. The math runs in one system under the hood, so a stray conversion can never sneak a mixed measurement into your cutting plan. Set it once and the app remembers, which means no half-inch, half-centimeter surprises when you sit down to cut.
The takeaway
Convert by multiplying: inches times 2.54 for centimeters, yards times 0.9144 for meters. Do it once at the start of a project, round up rather than down, and stay in a single unit the whole way through. If you would rather not think about it at all, get the app and let it hold the unit for you.