CraftCRAFTNUMA EDITORIAL · ENGLISH
From pattern to tape measure
A pattern says 36 inches. Your tape is marked in centimetres. Before you cut, bring both measurements into the same unit—and check what the number describes.
1. Identify the measurement
A line on a pattern, a body measurement and the length of fabric on a bolt may all be lengths, but they answer different questions. Write down the label beside the number before converting it. A 36-inch measurement does not, on its own, tell you a clothing size or how much fabric to buy.
Look for unit abbreviations: mm means millimetres, cm means centimetres, m means metres, in means inches, ft means feet and yd means yards. A double prime (″) commonly represents inches; a single prime (′) commonly represents feet. Check the pattern’s own legend when a mark is unclear.
2. Convert before rounding
One international inch is exactly 2.54 centimetres. To convert inches to centimetres, multiply by 2.54. To go back, divide by 2.54. For example, 36 × 2.54 = 91.44 cm. One yard equals 36 inches, so that same length is exactly one yard.
Keep the full converted value until you decide how to mark it on your ruler. If you round a value and repeatedly convert it back and forth, the rounded value can drift. The length converter calculates using the unrounded conversion factors; only the displayed result is rounded.
3. Handle fractions deliberately
For a measurement of 2½ inches, enter 2.5. The decimal comes from 2 + (1 ÷ 2). Common fractions are ¼ = 0.25, ½ = 0.5 and ¾ = 0.75. The converter accepts decimal numbers, not fraction strings such as “2 1/2”. It accepts either a decimal point or a decimal comma, but no thousands grouping. Enter one thousand as 1000.
Try this check: 2.5 inches becomes 6.35 centimetres. Change the direction and enter 6.35 cm; the result should return to 2.5 inches. This check confirms the arithmetic, but it cannot confirm whether you copied the original pattern measurement correctly.
4. Keep conversion separate from cutting decisions
The converter does not add seam allowances, estimate shrinkage or compensate for stretch. Read whether the pattern already includes seam allowances before adding anything. When fabric quantity is involved, check the specified fabric width, grain direction, pattern layout and any matching requirements. A length conversion alone cannot estimate the quantity needed for a garment.
A body measurement also does not select a universal clothing size. Sizing varies between patterns and brands, and intended garment ease changes the relationship between body measurements and finished dimensions. Use the measurement chart supplied with the pattern or garment you are making.
A quick check before cutting
- Confirm the measurement label and original unit.
- Convert once, then mark the result with a suitable ruler.
- Check the pattern instructions for allowances and layout.
- Recheck the copied number before making an irreversible cut.
About the conversion standard
The international inch is exactly 25.4 millimetres; the international yard is exactly 0.9144 metres. These definitions are documented by NIST: SI Units – Length. CraftNuma uses international units, not historical or survey units.