# Millimeter Converter URL: https://speedycalculator.com/calculators/conversion/millimeter-converter/ Last updated: 2026-10-25 > The millimeter converter converts length between centimetres, metres, inches, feet, micrometres, mils and more. Choose any “from” and “to” unit, type a number into any field and every other unit updates instantly; all conversion factors are exact definitions. ## Inputs - From (mm, m, km, cm, dm, µm, nm, Å, in, ft, yd, mi, nmi, mil, furlong, chain, rod, fathom, hand, league, AU, ly, pc, R☉, px (96 dpi), pt, gaj) ## Results - To - Metres - Inches - Feet - Micrometres - Mils ## Formula ``` 1 mm = 0.1 cm 1 mm = 0.001 m 1 mm = 0.039370079 in 1 mm = 0.0032808399 ft 1 mm = 1,000 µm ``` ## Explanation Millimetres are the unit of engineering drawings, rainfall, screen pitch and jewellery. One millimetre is 1,000 micrometres or about 0.03937 inches, so 25.4 mm is exactly one inch. ### How to use the Millimeter Converter - Pick the unit you are starting from in the **From** menu and type your value. - Pick the unit you want in the **To** menu. The heading changes to match – for example “Millimeters to Centimeters Converter”. - The most common length units are shown below at the same time, so you can compare them at a glance. - Type into any result to convert backwards, then use **Copy results** – the copied text starts with the heading for your chosen units. Results update as you type. Everything is calculated in your browser. ### How it works Every length unit is defined by an exact factor relative to the metre (the base unit). The calculator first turns the value you type into metres, then turns that into the unit you picked in the “To” menu and into each of the common units below it. This two-step method means any unit can be converted to any other – 27 units are available in each menu – and you can type into any field, including a result, to work in the other direction. Changing a unit menu keeps the quantity the same and just re-expresses it, and the page heading and copied results follow your choice. ### How to convert length units - Choose the unit you have in the **From** menu and type the value, for example **1 mm**. - Choose the unit you want in the **To** menu, for example centimetres. The page heading changes to “Millimeters to Centimeters Converter”. - The calculator multiplies by the metre factor of the “from” unit and divides by the factor of the “to” unit: 1 mm × 0.001 ÷ 0.01 = **0.1 cm**. ### 1 millimetre in common units UnitValueCentimetres (cm)0.1Metres (m)0.001Inches (in)0.039370079Feet (ft)0.0032808399Micrometres (µm)1,000Mils (mil)39.370079 ### Millimetres conversion table Millimetrescmminft0.50.050.00050.0196850390.001640419910.10.0010.0393700790.003280839920.20.0020.0787401570.006561679850.50.0050.196850390.0164041991010.010.393700790.03280839925.42.540.025410.083333333100100.13.93700790.32808399 ### What is a millimetre? A millimetre is one thousandth of a metre. Engineering drawings, construction plans, rainfall, screws, bolts and jewellery are all dimensioned in millimetres. ### What is a centimetre? A centimetre is one hundredth of a metre (10 mm). It is the everyday metric unit for body height, clothing, furniture and school rulers. ### What is a metre? The metre is the SI base unit of length. Since 1983 it has been defined as the distance light travels in a vacuum in 1/299,792,458 of a second, which ties it to a fundamental constant rather than a physical bar of metal. ### Common mistakes to avoid Mixing the international foot (0.3048 m) with the old u.s. survey foot, confusing nautical and statute miles, and writing decimal feet such as 5.5 ft as “5 ft 5 in” (it is 5 ft 6 in). ## Worked example Inputs — From: 1 mm. Results — **To = 0.1 cm**; Metres = 0.001 m; Inches = 0.03937008 in; Feet = 0.00328084 ft; Micrometres = 1,000 µm; Mils = 39.37007874 mil. ## FAQ **How many mm in an inch?** 25.4. **How many mm in a metre?** 1,000. **How thick is 1 mm?** About the thickness of a credit card’s edge (0.76 mm) plus a bit. **How do I change the units?** Pick any unit in the From and To menus. The value is converted in place, and the heading changes to show your conversion, for example “Millimeters to Centimeters Converter”. **Can I type into any field?** Yes. Every field is editable, so you can start from whichever unit you have. **How many units can I convert between?** 27 length units, from the everyday to the specialised. **Which units are exact?** All factors here are exact by definition except astronomical and similar reference values, which use internationally agreed constants. **What formula does the Millimeter Converter use?** 1 mm = 0.1 cm. ## Sources - [NIST Special Publication 811 – Guide for the Use of the International System of Units](https://www.nist.gov/pml/special-publication-811) - [NIST Handbook 44 Appendix C – General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)