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Converters Tools

Length converter

Pick two length units and type a number: the answer, the formula and the steps appear at once.

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  • Sources checked Oct 2026
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The answer updates as you type.

1 centimeter =

0.393701in

Also written as about 3/8 in on a tape measure

Formula: in = cm ÷ 2.54

Show the steps
  1. Definition: 1 cm = 0.01 m (SI prefix centi); 1 in = 2.54 cm exactly
  2. 1 cm ÷ 2.54 = 0.393701 in

Definitions used: 1 cm = 0.01 m (SI prefix centi); 1 in = 2.54 cm exactly.

Source: NIST SP 811, Appendix B.8, checked on .

Converting a whole column? Paste it all at once

Copy a column of centimeters from Excel or Google Sheets, paste it on the left and copy the inches on the right back into your sheet. One result per line, in the same order.

5 values converted.

Pasted numbers like 1,234.5, 1.234,5 and 1 234,5 are read correctly whatever the option above; it only changes how the results are written. If you paste several columns, the first one is used. Everything runs in your browser; nothing you paste is sent anywhere.

1 centimeter in every length unit

1 centimeters converted to each unit of length
UnitValue
Millimeters (mm)10
Meters (m)0.01
Kilometers (km)0.00001
Inches (in)0.393701
Feet (ft)0.0328084
Yards (yd)0.0109361
Miles (mi)0.00000621371
Nautical miles (nmi)0.00000539957

The table follows the amount and the “From” unit you set in the converter above.

Popular length conversions

How each length unit is defined

These are the definitions the converter uses, as written in the source next to each one. Nothing is rounded before the calculation.

Definitions of length units
UnitDefinitionIn meters
Millimeter (mm)1 mm = 0.001 m (SI prefix milli)0.001
Centimeter (cm)1 cm = 0.01 m (SI prefix centi)0.01
Meter (m)SI base unit of length1
Kilometer (km)1 km = 1000 m (SI prefix kilo)1,000
Inch (in)1 in = 2.54 cm exactly0.0254
Foot (ft)1 ft = 0.3048 m exactly (international foot)0.3048
Yard (yd)1 yd = 0.9144 m exactly0.9144
Mile (mi)1 mi = 1609.344 m exactly (5280 ft)1,609.344
Nautical mile (nmi)1 nautical mile = 1852 m exactly1,852

Length conversion questions

What is the difference between metric and US length units?

Metric units (mm, cm, m, km) go up in powers of ten from the meter. US customary units are tied to it by definition: 1 inch is exactly 2.54 cm, 1 foot is 12 inches, 1 yard is 3 feet and 1 mile is 5,280 feet.

What is a nautical mile?

A nautical mile is exactly 1,852 meters, used at sea and in aviation. It is about 15% longer than the statute mile of 1,609.344 meters.

Are these factors exact?

Yes. Inch, foot, yard and mile are defined in terms of the meter, so converting between them involves no measured constant, only arithmetic. NIST SP 811 marks them as exact.

Can I convert a whole column of values at once?

Yes. Use the box under the converter: copy the column from Excel or Google Sheets, paste it on the left and copy the converted column from the right. Each result sits on the same line as its original value. A line that is not a number, such as a header, is left blank so the rows stay aligned. If you paste several columns, the first one is converted.

Other converters

Every category uses the same layout: type a number, pick two units.

Sources and limits

  • NIST SP 811, Appendix B.8

    NIST Special Publication 811, Guide for the Use of the SI, Appendix B.8: Factors for Units Listed Alphabetically (page updated August 18, 2025).

    National Institute of Standards and Technology. Edition or effective date: . Text in force when checked on .

This is a calculation aid, not an official measurement service. Results are rounded to 6 significant digits for display. For trade, engineering, medical dosing or legal documents, confirm the figure in the official source. Nothing you type leaves your browser.