Inches to Centimeters Converter
Convert length between inches, centimeters, millimeters, meters, feet, and yards. Shows fractional inches and all unit conversions.
Inches to Centimeters Converter
Calculator
Adjust values & calculateEnter your values below. Every result is computed in your browser — no data is sent to any server.
Formula: cm = in x 2.54 | in = cm / 2.54 | 1 ft = 12 in | 1 yd = 3 ft
Worked example — 55 in = 139.7 cm = 4 ft 7 in = 1.397 m
Formula
cm = in x 2.54 | in = cm / 2.54 | 1 ft = 12 in | 1 yd = 3 ft
All length conversions use millimeters as the base unit. One inch is exactly 25.4 mm (2.54 cm) by international agreement since 1959. One foot is 12 inches (304.8 mm), and one yard is 3 feet (914.4 mm). Metric units scale by powers of 10: 1 m = 100 cm = 1000 mm.
Worked Examples
Example 1: TV Screen Size
Problem:Convert a 55-inch TV diagonal to centimeters.
Solution:cm = inches x 2.54 cm = 55 x 2.54 = 139.7 cm Also: 55 in = 4 ft 7 in = 1.397 m
Result:55 in = 139.7 cm = 4 ft 7 in = 1.397 m
Example 2: Height Conversion
Problem:Convert a height of 175 cm to feet and inches.
Solution:Inches = 175 / 2.54 = 68.8976 in Feet = 68.8976 / 12 = 5 ft remainder 8.8976 in Fractional: 5 ft 8 7/8 in Meters: 1.75 m
Result:175 cm = 68.9 in = 5 ft 8 7/8 in
Frequently Asked Questions
How do I convert inches to centimeters?
To convert inches to centimeters, multiply the length in inches by 2.54. This is an exact conversion factor — 1 inch is defined as exactly 2.54 centimeters. For example, 12 inches = 12 x 2.54 = 30.48 cm. For a quick mental estimate, multiply inches by 2.5. So 8 inches is approximately 8 x 2.5 = 20 cm (actual: 20.32 cm). This conversion is commonly used in construction, tailoring, and international product specifications.
What are fractional inches and how are they used?
Fractional inches express measurements as fractions (1/2, 1/4, 1/8, 1/16, 1/32, 1/64) rather than decimals. They're standard in US construction, woodworking, plumbing, and hardware. A tape measure is typically marked in 1/16" increments. To convert decimal inches to fractions: multiply the decimal by 16, round to the nearest whole number, and express as that number over 16, then simplify. For example, 0.375" = 0.375 x 16 = 6/16 = 3/8". This converter shows the nearest 1/16" fraction.
How do I convert between feet and meters?
1 foot equals exactly 0.3048 meters (or 30.48 cm). To convert feet to meters, multiply by 0.3048. To convert meters to feet, multiply by 3.2808. For example, 6 feet = 6 x 0.3048 = 1.8288 meters. A useful approximation: 1 meter is about 3 feet 3 inches. For height: 5'10" (70 inches) = 1.778 m. Feet and meters are the most commonly cross-referenced length units in international construction, aviation, and athletics.
Why is an inch exactly 2.54 centimeters?
In 1959, the international yard was officially defined as exactly 0.9144 meters by agreement among six English-speaking nations (US, UK, Canada, Australia, New Zealand, and South Africa). Since 1 yard = 36 inches and 1 yard = 0.9144 m, this makes 1 inch = 0.9144/36 = 0.0254 meters = 2.54 centimeters exactly. Before this standardization, the inch varied slightly between countries. This definition ties the imperial/US customary system directly to the metric system.
How do you convert square inches and cubic inches to metric?
Area and volume factors are the linear factor raised to a power, not the linear factor itself. Since 1 inch is exactly 2.54 centimetres, 1 square inch is 2.54 squared, or 6.4516 square centimetres, and 1 cubic inch is 2.54 cubed, or 16.387064 cubic centimetres, which is also 16.387064 millilitres. So a 300 cubic inch engine displaces 300 x 16.387064 = 4,916 cubic centimetres, about 4.9 litres. Forgetting to square or cube the factor produces an answer wrong by a factor of 2.54 or 6.45, and it is the most frequent conversion mistake.
What is the difference between the international inch and the US survey inch?
The international inch, adopted in 1959, is exactly 2.54 centimetres. The older US survey inch derives from a survey foot defined as 1200/3937 metres, making it about 2 parts per million longer. The gap is invisible on a workbench, amounting to roughly 2 millimetres over a kilometre, but it accumulates in state plane coordinates and long survey lines, which is why legacy US land data specified which foot was intended. The survey foot has since been retired in favour of the international foot, so current work should use 2.54 exactly.
How do you convert millimetres to inches for machining tolerances?
Divide millimetres by 25.4, since an inch is exactly 25.4 millimetres. The useful landmark is that one thousandth of an inch, a thou or mil, equals 25.4 micrometres or 0.0254 millimetres. So a tolerance of plus or minus 0.01 mm is about 0.0004 inch, and 0.001 inch is about 0.025 mm. When converting a toleranced dimension, convert the upper and lower limits rather than the nominal and the tolerance separately, and never round the converted limits outward, since that quietly loosens the specification.
Why are screens and wheel rims still sized in inches in metric countries?
Because these are industry conventions rather than legal measurement requirements, and the tooling, part numbering and buyer expectations were all established in inches. A television is described by its diagonal in inches worldwide, and a wheel rim diameter is in inches even where every road sign is metric. Tyre markings show the hybrid plainly: in 205/55 R16 the section width is 205 millimetres and the aspect ratio is a percentage, but the 16 is the rim diameter in inches. Converting these designations to centimetres is arithmetically valid but will not match any catalogue.
How many decimal places should a converted inch value keep?
Keep only the precision the original measurement actually had. A board measured to the nearest sixteenth of an inch is known to about 1.6 millimetres, so writing the converted value as 121.4453125 mm implies an accuracy that does not exist; 121.4 mm is honest. As a rule of thumb, carry the same number of significant figures through the conversion, do any intermediate arithmetic at full precision, and round only once at the end so repeated rounding does not accumulate into a visible error.
Is a 30 cm ruler the same length as a one-foot rule?
Close, but not equal. A foot is 12 inches, which is 30.48 cm, so a 30 cm ruler falls 4.8 mm short of a foot, and 30 cm is about 11.81 inches. The difference is under two percent, which is why the two are used interchangeably in schools, but it is enough to matter when a 30 cm scale is used to step off repeated marks along a long run, because the shortfall multiplies with every repetition.
References
Background & Theory
1 inch = 2.54 centimetres exactly, and 1 centimetre = 0.393700787 inches. The inch is defined as exactly 25.4 millimetres, so inch-to-metric conversion is a definition rather than a measured ratio; only the reverse direction has to be rounded.
Conversion reference table
| Conversion | Equivalent | Exact or rounded? |
|---|---|---|
| 1 inch | 2.54 centimetres = 25.4 millimetres | Exact by definition |
| 1 centimetre | 0.393700787 inches | Derived, rounded |
| 1 foot (12 in) | 30.48 centimetres | Exact |
| 1 yard (36 in) | 0.9144 metres | Exact |
| 1 metre | 39.3700787 inches | Derived, rounded |
| 1 mil / thou | 25.4 micrometres | Exact |
| 1 point (DTP, 1/72 in) | 0.352777... millimetres | Exact fraction, non-terminating |
The 25.4 mm definition dates from the 1959 International Yard and Pound Agreement, which harmonised the slightly different British and American inches then in use. One legacy exception survived until recently: the US survey inch, based on a foot of 1200/3937 metres, ran about two parts per million longer and was retired at the end of 2022. Unless you are working with pre-2023 American land survey records, the 25.4 mm inch is the only one you need.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
Related Calculators
🧮Pixels to Inches Converter
Calculate pixelsto inches converter with inputs, formulas, and instant results.
🧮Height to Centimeters Converter
Calculate height to centimeters converter with inputs, formulas, and instant results.
🧮Square Feet to Square Meters Converter
Convert between square feet, square meters, square yards, and square inches.
🧮Cubic Yards to Cubic Feet Converter (yd³ to ft³)
Convert between cubic yards, cubic feet, cubic meters, and cubic inches.
🧮Paper Size Converter
Convert between A-series (A4, A3), US Letter, Legal, and other paper sizes in mm and inches.
🧮Nm to Kgf-Cm Converter
Convert torque between Newton-meters and kilogram-force centimeters.