ManyConvert mm to inches
1 millimeter = 0.03937008 inches. Type a value below for an instant mm to inches conversion, or use the table for common values.
| Millimeters | Inches |
|---|---|
| 1 mm | 0.03937008 in |
| 2 mm | 0.07874016 in |
| 3 mm | 0.1181102 in |
| 4 mm | 0.1574803 in |
| 5 mm | 0.1968504 in |
| 10 mm | 0.3937008 in |
| 15 mm | 0.5905512 in |
| 20 mm | 0.7874016 in |
| 25 mm | 0.984252 in |
| 30 mm | 1.181102 in |
| 40 mm | 1.574803 in |
| 50 mm | 1.968504 in |
| 75 mm | 2.952756 in |
| 100 mm | 3.937008 in |
How millimetres convert to inches
There are exactly 25.4 millimetres in an inch, so inches = mm ÷ 25.4.
In your head: divide by 100 and multiply by 4. For 50 mm that gives 2 inches; the true figure is 1.97.
Matching millimetres to fractional inches
Inch-based tools and fasteners come in fractions, not decimals, so the useful question is usually “which fraction is this close to?”
| Fraction of an inch | Decimal inches | Millimetres |
|---|---|---|
| 1/16 | 0.0625 | 1.59 |
| 1/8 | 0.125 | 3.18 |
| 1/4 | 0.25 | 6.35 |
| 3/8 | 0.375 | 9.53 |
| 1/2 | 0.5 | 12.70 |
| 5/8 | 0.625 | 15.88 |
| 3/4 | 0.75 | 19.05 |
| 1 | 1 | 25.40 |
Near matches are not matches
A 10 mm bolt is 0.394 in, close to 3/8 in at 0.375 — but a 3/8 spanner will not fit a 10 mm head, and a 10 mm one will round off a 3/8. The same goes for drill bits and pipe fittings. Where parts have to fit, use the size that was specified rather than its nearest equivalent. Of the common sizes only a few pairs are near enough to swap in a pinch, such as 19 mm and 3/4 in.
Where millimetres turn up
Engineering drawings, plywood and glass thickness, jewellery, camera lens focal lengths, rainfall, and screws and bolts are all quoted in millimetres. Thin sheet and wire are sometimes given in thousandths of an inch, called “thou” or “mil”: 1 mm is 39.37 thou, which has nothing to do with a millimetre despite the name.
Convert mm to inches quickly and accurately with this free tool. 1 millimeter = 0.03937008 inches. For every other unit, use the full ManyHand Unit Converter.
How do I convert mm to inches?
Multiply the number of millimeters by 0.03937008. For example, 10 mm = 0.3937008 in. You can also type any value in the converter above.
What is 1 millimeter in inches?
1 millimeter equals 0.03937008 inches. Conversely, 1 inch equals 25.4 millimeters.
Is this mm to inches converter free?
Yes. It's free with no sign-up, works on phone and desktop, and runs entirely in your browser.