Inches and centimeters explained
The inch and the centimeter meet at one exact number. This guide covers the formula, fractions, heights and how much to round.
Open the tool: Inches to cm converter
Why 2.54?
Before 1959 the US and UK inches were very slightly different. The international yard and pound agreement fixed the inch at exactly 25.4 mm, so 2.54 cm is an exact number, not a rounded one.
Converting fractions
Divide the top number by the bottom number and add the whole inches: 7 5/16 inches is 7 + 5 ÷ 16 = 7.3125 inches, or 18.574 cm. To go back, divide cm by 2.54 and multiply the decimal part by 16 to find the nearest sixteenth.
Heights in feet and inches
Multiply the feet by 12, add the inches, then multiply by 2.54. 6'2" is 74 inches, which is 187.96 cm. Most forms round heights to the nearest centimeter.
How much to round
- Sewing and crafts: the nearest millimeter or 1/8 inch.
- Woodworking: 1/16 inch, or 1/32 inch for fine joinery.
- Engineering drawings: keep the exact value and round only at the end.
- Body height and screen sizes: the nearest whole centimeter.