MM to Inches Converter
Quick answer: To convert MM to inches, multiply by 0.03937008. For example, 10 mm is 0.3937008 in. One millimeter equals 0.03937008 in.
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Use the MM to Inches Converter
MM to Inches formula and what each symbol means
in = mm × 0.03937008
| Symbol | Meaning |
|---|---|
| mm | Millimeter |
| in | Inch |
MM to Inches examples
1 mm
1 mm × 0.03937008 = 0.03937008 in.
10 mm
10 mm × 0.03937008 = 0.3937008 in.
100 mm
100 mm × 0.03937008 = 3.937008 in.
MM compared with Inches
One in is 25.4 times as large as one mm, so your number gets smaller when you convert MM to inches and bigger when you convert back. If the answer is not smaller than what you typed, you multiplied instead of dividing.
About MM and inches
Millimeter (mm): One thousandth of a metre. Inch (in): The international inch, exactly 2.54 centimetres.
Where MM to inches conversions are used
Road distances and maps use kilometres or miles, while building plans use metres, millimetres or feet. Screen sizes, tyres and clothing are usually given in inches, and body measurements in centimetres or inches.
How to calculate MM to Inches step by step
- Enter the value in mm (the starting unit).
- Multiply by 0.03937008, because 1 mm = 0.03937008 in.
- The product is the value in in. To go back, divide by 0.03937008 or multiply by 25.4.
Popular length conversions
How to read your MM to Inches result
Quick estimate: multiply by about 0.04 to get inches from MM; this is within 1.6% of the exact factor. Metric lengths convert by powers of ten, so you only move the decimal point.
| MM | INCHES |
|---|---|
| 1 | 0.03937008 |
| 2 | 0.07874016 |
| 5 | 0.1968504 |
| 10 | 0.3937008 |
| 20 | 0.7874016 |
| 50 | 1.968504 |
| 100 | 3.937008 |
| 1,000 | 39.37008 |
Inches to MM: quick table
| INCHES | MM |
|---|---|
| 1 | 25.4 |
| 5 | 127 |
| 10 | 254 |
| 25 | 635 |
| 50 | 1,270 |
| 100 | 2,540 |
| 250 | 6,350 |
| 500 | 12,700 |
Common mistakes when calculating MM to Inches
- Mixing the international foot with the older US survey foot: the difference is about 2 parts per million and only matters in large land surveys.
- Dividing when you should multiply: from mm to in multiply by 0.03937008; from in to mm divide by 0.03937008.
MM to Inches FAQ
How many in are in 1 mm?
1 mm equals 0.03937008 in.
How many mm are in 1 in?
1 in equals 25.4 mm.
Is 1 mm = 0.03937008 in an exact conversion?
Yes. The millimeter and the inch are both defined exactly in SI terms, so the ratio has no measurement uncertainty; 0.03937008 is just that ratio shown to 7 significant figures.
What is a millimeter (mm)?
One thousandth of a metre.
How can I estimate MM to inches in my head?
Quick estimate: multiply by about 0.04 to get inches from MM; this is within 1.6% of the exact factor.
What is 0.5 mm in inches?
0.5 mm = 0.01968504 in (since 0.5 × 0.03937008).
What is 25 mm in inches?
25 mm = 0.984252 in (since 25 × 0.03937008).
What is 80 mm in inches?
80 mm = 3.149606 in (since 80 × 0.03937008).
How many decimals should I keep when converting mm to in?
Match the precision of your original measurement. For example, 0.3937008 in rounds to 0.394 in at 3 significant figures; keep more digits only for engineering or scientific work.
More in Length converters
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- Miles to Meters Converter
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Method, review and disclaimer
Edited by: Hemant Kumar and Anjita Rai, founders of ToolsVault (SEO and content professional, not a licensed adviser). Method: this tool runs in your browser using the formula shown on this page; the numbers you enter are not sent to our servers. Sources: NIST SP 811, Appendix B.8: conversion factors, BIPM: the SI base units