Free Inches to Cm Converter
Published: 14 November 2026 · Updated: 14 November 2026
Type a length in inches and the exact value in centimetres appears instantly. US and UK listings — screens, luggage, clothing, bike parts — usually quote inches, while European shops and workshops use centimetres, so this converter bridges the two. It starts with 12 inches, which is exactly 30.48 cm. For the reverse direction, use the Free Cm to Inches Converter.
1 inch is exactly 2.54 cm, so multiply any inch value by 2.54. That makes 12 inches exactly 30.48 cm — one foot, with no rounding at all. The factor is a definition agreed in 1959, not a measured estimate, so a 27-inch screen is exactly 68.58 cm across the diagonal.
Researched by MixKhazana Team · Last updated 14 November 2026 · Data: NIST SP 811; BIPM SI Brochure; International Yard and Pound Agreement 1959
What is an inch?
An inch (in) is a unit of length in the imperial and US customary systems, equal to exactly 25.4 millimetres. There are 12 inches in a foot and 36 inches in a yard.
Before 1959 the inch differed slightly between countries; the International Yard and Pound Agreement fixed it at 25.4 mm everywhere, which is why inch-to-centimetre conversion today is exact. Inches remain standard for screen sizes, wheel diameters, fasteners and heights in the United States, and are still widely used in the United Kingdom.
What is a centimetre?
A centimetre (cm) is one hundredth of a metre: 1 cm = 0.01 m, and 1 cm = 10 mm. It is the standard everyday metric unit across Europe for heights, clothing sizes, furniture and paper.
Centimetres are used wherever metres would need awkward decimals: a person is 178 cm rather than 1.78 m, and a shelf is 60 cm deep rather than 0.6 m. The American spelling is centimeter; the unit is identical.
How to use this converter
- Type your length in the inches box — the centimetre value appears as you type.
- Fractions are fine as decimals: type 5.5 for 5 1/2 in, or 3.25 for 3 1/4 in.
- To convert the other way, type in the centimetres box, or press Swap direction to flip the converter and carry the converted value over.
- The result line shows the exact conversion plus the reverse rate, 1 cm = 0.3937 in.
Inches to centimetres formula
Let Lin be the length in inches and Lcm be the same length in centimetres:
- Centimetres from inches: Lcm = Lin × 2.54
- Inches from centimetres: Lin = Lcm ÷ 2.54
Because 2.54 is exact, multiplying and then dividing returns the original number — try it with the Swap button. Our metric vs imperial conversion guide for Europe explains where each system is used and why both survive.
Worked example
A laptop is advertised with a 15.6-inch screen, and you want the diagonal in centimetres:
- Multiply by the exact factor: 15.6 × 2.54
- Split it up: 15 × 2.54 = 38.10, and 0.6 × 2.54 = 1.524
- Add the parts: 38.10 + 1.524 = 39.624 cm, about 39.62 cm
- Check: 39.624 ÷ 2.54 = 15.6 in, back where we started
So the screen measures 39.62 cm diagonally — before adding the bezel. Try 15.6 in the converter above.
Inches to centimetres conversion table
| Inches (in) | Centimetres (cm) |
| 1 | 2.54 |
| 2 | 5.08 |
| 3 | 7.62 |
| 4 | 10.16 |
| 5 | 12.7 |
| 6 | 15.24 |
| 8 | 20.32 |
| 9 | 22.86 |
| 10 | 25.4 |
| 12 | 30.48 |
| 15 | 38.1 |
| 18 | 45.72 |
| 24 | 60.96 |
| 36 | 91.44 |
| 48 | 121.92 |
| 60 | 152.4 |
Centimetres are shown to four decimal places; whole-inch values convert to exact two-decimal centimetre values.
Everyday benchmarks: inch sizes you meet in centimetres
These inch sizes appear in shops and listings every day — here they are in centimetres:
- 12-inch ruler — 30.48 cm. The classic school ruler is just over 30 cm long.
- 27-inch monitor — 68.58 cm. The diagonal of a popular desk monitor, measured corner to corner.
- 6-foot person — 72 in = 182.88 cm. Six feet is 183 cm rounded, a height given in feet and inches in the UK and US.
- 10-inch tablet — 25.4 cm. A 10-inch screen diagonal is exactly 25.4 cm.
- 12-inch pizza — 30.48 cm. A medium pizza is about 30 cm across.
- US Letter paper — 8.5 × 11 in = 21.59 × 27.94 cm. Slightly shorter and wider than A4 (21 × 29.7 cm).
- 20-inch bike wheel — 50.8 cm. A common folding-bike and BMX wheel size.
Need another unit? The Free Unit Converter covers more units — including feet, metres, miles, weight and temperature — in a single tool.
Frequently asked questions
How do you convert inches to cm?
Multiply the inch value by 2.54. For example, 8 in × 2.54 = 20.32 cm. The factor is exact, because the inch has been defined as 25.4 mm since 1959.
What is 12 inches in cm?
12 inches is exactly 30.48 cm. Twelve inches make one foot, so one foot is 30.48 cm by definition — a figure worth remembering when reading US height and room measurements.
How many cm is 5 feet 7 inches?
5 feet 7 inches is 67 inches in total (5 × 12 + 7), and 67 × 2.54 = 170.18 cm. So 5 ft 7 in is about 170 cm.
What is 1 inch in cm?
1 inch is exactly 2.54 cm. This is a definition agreed in 1959, not a rounded measurement, so it applies everywhere and never changes.
Is the inch a metric or imperial unit?
The inch is an imperial and US customary unit, but it is defined in metric terms: exactly 25.4 millimetres. That definition is what makes inch-to-centimetre conversion exact instead of approximate.
How do I convert inches with fractions, like 5 1/2 in?
Turn the fraction into a decimal first, then multiply by 2.54. For 5 1/2 in, type 5.5: 5.5 × 2.54 = 13.97 cm. Common fractions: 1/4 = 0.25, 1/2 = 0.5, 3/4 = 0.75.
Why do European shops list TV sizes in inches?
Screen sizes follow an industry convention that stayed in inches worldwide, even in metric countries. A 55-inch TV is 55 × 2.54 = 139.7 cm across the diagonal, and a 65-inch TV is 165.1 cm.
Can this converter handle decimal inches?
Yes. Type any decimal, such as 3.25 in, and the converter multiplies it by 2.54 straight away: 3.25 in = 8.255 cm. Fractions must be typed as decimals, for example 0.5 for one half.
Sources
- NIST Special Publication 811 — Guide for the Use of the International System of Units (SI), conversion factors for the inch, foot and yard.
- BIPM SI Brochure — the International System of Units, definitions of the metre, centimetre and millimetre.
- International Yard and Pound Agreement, 1959 — 1 yard = 0.9144 m exactly, giving 1 in = 25.4 mm and 1 ft = 0.3048 m exactly.
Disclaimer: conversions use the exact defined factor (1 in = 2.54 cm); for buying screens or furniture, also check the full product dimensions.