Inches to CM converter, inches to centimeters, fractions too.

To convert inches to cm, multiply the inches by 2.54. So 1 inch is 2.54 cm, 12 inches is 30.48 cm and 36 inches is 91.44 cm. There is no rounding in that sum: 2.54 is exact, so an inch value written as a decimal, or as a fraction with a power of two below the line, gives a short answer that ends. The type box accepts fractions, so a measurement read off a tape such as 5 3/8 goes straight in.

How to use the converter

1. Type a length in the Inches (in) box. Whole numbers, decimals and fractions such as 5 3/8, 3/16 or ½ all work.
2. The big result shows centimeters. The cards under it show the same length in millimeters, feet and inches and meters.
3. Use the Up and Down arrow keys to nudge the number by 1. Hold Shift for 10 or Alt for 0.1.
4. Choose Decimals to fix the places, for example 1 for clothing or 2 for a part.
5. Click a row in Common values to load it, or press Print chart for a sheet of sizes to pin up.

The definition: exactly 2.54

The international inch is exactly 2.54 centimeters, which is 25.4 millimeters or 0.0254 meters. NIST Handbook 44 (2026), Appendix C states "1 inch (in) 2.54 centimeters (exactly)" and gives 1 foot as 0.3048 meter exactly. NIST Special Publication 811, Appendix B.8 lists the inch to centimeter factor as 2.54 and marks it exact. Both were checked 18 Oct 2026. In practice this means an inches to cm answer ends: 5 3/8 inches is 13.6525 cm, with no digits dropped.

Mental shortcut and its error

Multiply by 2.5, then add about 2 percent. For 8 inches: 8 × 2.5 = 20, and 2 percent of 20 is 0.4, so 20.4 cm. The exact answer is 20.32 cm. Without the correction, 8 × 2.5 = 20 is 1.57 percent low, which is 0.32 cm short on 8 inches. For fast checking, remember 4 inches is 10.16 cm and 10 inches is 25.4 cm.

Worked examples

• A 15.6 inch laptop screen. 15.6 × 2.54 = 39.624 cm measured along the diagonal.
• A 5 3/8 inch board width. 5 3/8 is 5.375. 5.375 × 2.54 = 13.6525 cm, or 136.525 mm.
• A waist of 32 inches. 32 × 2.54 = 81.28 cm. A 30 inch waist is 76.2 cm.
• A person 5 ft 10 in tall. That is 5 × 12 + 10 = 70 inches. 70 × 2.54 = 177.8 cm, or 1.778 m.
• A 1/16 inch gap. 1/16 is 0.0625. 0.0625 × 2.54 = 0.15875 cm, which is 1.5875 mm.

A mistake to watch: the fraction read wrong

The typical error with inches is the tape, not the sum. 5/16 is not 0.516. It is 5 ÷ 16 = 0.3125. A reading of 2 5/16 inches is therefore 2.3125 inches, or 5.87375 cm. Type the fraction as it is and let the converter do the division. The second slip is mixing up inch marks: the double tick (") means inches and the single tick (') means feet. 5'10" is 70 inches, not 5.10.

Screen sizes in inches and centimeters

Screens, TVs and tablets are sold by their diagonal in inches. The table gives the diagonal in centimeters, exact to one place. It is the diagonal only. The width and height depend on the aspect ratio.

If you need the pixel density of a screen from its diagonal, the same factor is used inside the PPI calculator, which divides the diagonal in pixels by the diagonal in inches.

Rounding for the job

For clothing, round to the nearest half centimeter. For furniture, round up when you check that something fits and down when you check that a space is big enough. For machine parts, keep at least two decimals, and use millimeters instead: 1 inch is 25.4 mm, so a quarter inch is 6.35 mm, an eighth is 3.175 mm and a sixteenth is 1.5875 mm. Those three are all exact. The calculator shows what it rounds, so you see 5 3/8 inches as 13.6525 cm and not a shorter guess.

Who uses inches to cm

Anyone with a US size and a metric need: ordering clothes or shoes from abroad, checking a monitor or TV size, fitting a bike frame, reading a furniture spec or a pipe size, passing a measurement to a supplier in another country. Wood and metal work often needs millimeters, so the cards give them as well. If you work in whole millimeters, go straight to the Inch to MM converter.

For the other direction, use the CM to inches converter.