This converter turns millimeters into inches instantly, using the exact factor 1 millimeter = 0.03937007874 inches. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
One thousandth of a metre — the finest gradation on a standard ruler. Exactly 25.4 millimetres since the 1959 international yard agreement.
Because the relationship is a simple proportion, one multiplication does the whole job. The table further down gives pre-computed values for the amounts people look up most often, and the result panel also reports the reverse conversion so you can check the figure both ways.
The formula
millimeters- The amount you are converting, measured in millimeters
0.03937007874- The exact number of inches in one millimeter
inches- The converted result
How it works, step by step
- Enter the number of millimeters you want to convert.
- The value is multiplied by 0.03937007874, the exact conversion factor.
- The result is displayed in inches, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 millimeters
Multiply 5 by 0.039370079. That gives 0.19685 inches. A quick sanity check: one millimeter is smaller than one inch, so the number should get smaller — and it does.
Converting 72 millimeters
72 × 0.039370079 = 2.8346 inches. Working backwards, 2.8346 ÷ 0.039370079 returns 72 millimeters, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many inches are in one millimeter?
Exactly 0.03937007874. Every conversion on this page is that single number multiplied by your input, so the result carries no rounding error beyond what is shown.
What is the formula to convert millimeters to inches?
Inches = millimeters × 0.03937007874. To reverse it, divide instead: millimeters = inches ÷ 0.03937007874, which is the same as multiplying by 25.4.
Is the millimeter bigger than the inch?
No. One millimeter is only 0.0393701 of a inch, so the inch is the larger unit.
Why does my answer differ slightly from other mm to inches converters?
Most differences come from rounding the factor too early. This tool keeps full double precision through the calculation and only rounds at the final display step, and it also shows the unrounded value so you can see exactly where any difference appears.
What is a millimeter?
One thousandth of a metre — the finest gradation on a standard ruler.
What is a inch?
Exactly 25.4 millimetres since the 1959 international yard agreement.
Millimeters to inches reference table
| Millimeters | Inches |
|---|---|
| 0.5 mm | 0.019685 in |
| 1 mm | 0.03937 in |
| 2 mm | 0.07874 in |
| 3 mm | 0.11811 in |
| 5 mm | 0.19685 in |
| 10 mm | 0.393701 in |
| 15 mm | 0.590551 in |
| 20 mm | 0.787402 in |
| 25 mm | 0.984252 in |
| 50 mm | 1.9685 in |
| 75 mm | 2.9528 in |
| 100 mm | 3.937 in |
| 250 mm | 9.8425 in |
| 500 mm | 19.685 in |
| 1000 mm | 39.3701 in |
Exact factor: 1 millimeter = 0.03937007874 inches. Values rounded for display.