Inches to cm and mm for screens, waists and tools

Formula: cm = in × 2.54.

Multiply the inches by 2.54. Because the inch is defined as exactly 25.4 mm, there is nothing to round in the factor. Worked example for a 15.6-inch laptop screen: 15.6 × 2.54 = 39.624 cm across the diagonal.

For a fraction such as 3/8 in, divide first: 3 ÷ 8 = 0.375 in, then 0.375 × 2.54 = 0.9525 cm, or 9.525 mm. Multiplying by 25.4 instead gives millimetres directly, which is what engineering drawings and bolt sizes use.

• Centimetres to inches: the reverse direction, in = cm × 0.393700787402

Each row is computed with the same exact factor as the converter above and rounded only for display.

• The diagonal of a 6.1-inch phone screen: 6.1 in = 15.49 cm.
• A 27-inch monitor, measured corner to corner: 27 in = 68.58 cm.
• A 32-inch waist on US jeans: 32 in = 81.28 cm.
• A 12-inch pizza or a 1-foot ruler: 12 in = 30.48 cm.
• A half-inch wrench or pipe fitting: 0.5 in = 1.27 cm.

1. Type the value in the first box; the converted value appears in the second box as you type.
2. Or type in the second box to convert the other way.
3. Use the Decimals menu to round, and the quick-reference table for common values.