How many inches are in 1 millimeter?

1 mm equals 0.03937007874 in. This is an exact conversion factor defined by NIST.

How do I convert millimeters to inches?

Multiply the value in mm by the conversion factor. For example, 10 mm = 0.3937007874 in. Use our calculator above for instant results.

Is the millimeters to inches conversion exact?

Yes, this conversion is mathematically exact based on the international definition of these units (NIST SP 811).

Can I convert millimeters to inches offline?

Yes! OmniConvert runs entirely in your browser — no internet connection needed after the page loads. Your data never leaves your device, ensuring complete privacy.

What is the difference between millimeters and inches?

Millimeters (mm) and Inches (in) are both units of length but belong to different measurement systems. 1 mm = 0.03937007874 in. Use the converter above to switch between them instantly.

Millimeters to Inches (mm → in) — Free Online Converter

mm → in Reference Table

mm	in
0.001 mm	0.00003937007874 in
0.002 mm	0.00007874015748 in
0.003 mm	0.0001181102362 in
0.004 mm	0.000157480315 in
0.005 mm	0.0001968503937 in
0.006 mm	0.0002362204724 in
0.007 mm	0.0002755905512 in
0.008 mm	0.0003149606299 in
0.009 mm	0.0003543307087 in
0.01 mm	0.0003937007874 in
0.02 mm	0.0007874015748 in
0.03 mm	0.001181102362 in
0.04 mm	0.00157480315 in
0.05 mm	0.001968503937 in
0.06 mm	0.002362204724 in
0.07 mm	0.002755905512 in
0.08 mm	0.003149606299 in
0.09 mm	0.003543307087 in
0.1 mm	0.003937007874 in
0.2 mm	0.007874015748 in
0.3 mm	0.01181102362 in
0.4 mm	0.0157480315 in
0.5 mm	0.01968503937 in
0.6 mm	0.02362204724 in
0.7 mm	0.02755905512 in
0.8 mm	0.03149606299 in
0.9 mm	0.03543307087 in
1 mm	0.03937007874 in
1.5 mm	0.05905511811 in
2 mm	0.07874015748 in
2.5 mm	0.09842519685 in
3 mm	0.1181102362 in
3.5 mm	0.1377952756 in
4 mm	0.157480315 in
4.5 mm	0.1771653543 in
5 mm	0.1968503937 in
5.5 mm	0.2165354331 in
6 mm	0.2362204724 in
6.5 mm	0.2559055118 in
7 mm	0.2755905512 in
7.5 mm	0.2952755906 in
8 mm	0.3149606299 in
8.5 mm	0.3346456693 in
9 mm	0.3543307087 in
9.5 mm	0.374015748 in
10 mm	0.3937007874 in
11 mm	0.4330708661 in
12 mm	0.4724409449 in
13 mm	0.5118110236 in
14 mm	0.5511811024 in
15 mm	0.5905511811 in
16 mm	0.6299212598 in
17 mm	0.6692913386 in
18 mm	0.7086614173 in
19 mm	0.7480314961 in
20 mm	0.7874015748 in
25 mm	0.9842519685 in
30 mm	1.181102362 in
35 mm	1.377952756 in
40 mm	1.57480315 in
45 mm	1.771653543 in
50 mm	1.968503937 in
55 mm	2.165354331 in
60 mm	2.362204724 in
65 mm	2.559055118 in
70 mm	2.755905512 in
75 mm	2.952755906 in
80 mm	3.149606299 in
85 mm	3.346456693 in
90 mm	3.543307087 in
95 mm	3.74015748 in
100 mm	3.937007874 in
120 mm	4.724409449 in
125 mm	4.921259843 in
130 mm	5.118110236 in
140 mm	5.511811024 in
150 mm	5.905511811 in
160 mm	6.299212598 in
175 mm	6.88976378 in
180 mm	7.086614173 in
200 mm	7.874015748 in
225 mm	8.858267717 in
250 mm	9.842519685 in
275 mm	10.82677165 in
300 mm	11.81102362 in
350 mm	13.77952756 in
400 mm	15.7480315 in
450 mm	17.71653543 in
500 mm	19.68503937 in
600 mm	23.62204724 in
700 mm	27.55905512 in
750 mm	29.52755906 in
800 mm	31.49606299 in
900 mm	35.43307087 in
1000 mm	39.37007874 in
1200 mm	47.24409449 in
1250 mm	49.21259843 in
1500 mm	59.05511811 in
1750 mm	68.8976378 in
2000 mm	78.74015748 in
2500 mm	98.42519685 in
3000 mm	118.1102362 in
4000 mm	157.480315 in
4500 mm	177.1653543 in
5000 mm	196.8503937 in
6000 mm	236.2204724 in
7000 mm	275.5905512 in
7500 mm	295.2755906 in
8000 mm	314.9606299 in
9000 mm	354.3307087 in
10000 mm	393.7007874 in
15000 mm	590.5511811 in
20000 mm	787.4015748 in
25000 mm	984.2519685 in
50000 mm	1968.503937 in
75000 mm	2952.755906 in
100000 mm	3937.007874 in

Values based on NIST SP 811 conversion factors

Why Convert Millimeters to Inches?

Converting between millimeters (mm) and inches (in) is one of the most common length conversions. Whether for engineering, cooking, travel, or science, knowing how to quickly convert mm to in saves time and prevents errors.

Length conversions between mm and in are fundamental in construction, manufacturing, and international trade. Architects rely on precise conversions when adapting building plans between metric and imperial standards — a 1% error on a 30-meter wall translates to 30 cm of misalignment. Travelers frequently convert between kilometers and miles for road trips, while online shoppers need length conversions to verify clothing sizes, furniture dimensions, and screen diagonals across international retailers. In athletics, track distances (100m, 1500m, marathon) must be precisely converted for record comparisons across different measurement traditions.

How to Convert Millimeters to Inches

To convert millimeters to inches, use the following formula:

in = mm × 0.03937007874

Example: 1 mm = 0.03937007874 in

For example, 5 mm = 0.1968503937 in, 10 mm = 0.3937007874 in, and 100 mm = 3.937007874 in. For larger values, 1000 mm = 39.37007874 in. Conversely, 1 in = 25.4 mm. Our calculator above performs this conversion instantly with full precision — no rounding errors.

Common Use Cases

iPhone 15 Pro thickness (8.25 mm): 8.3 mm = 0.3267716535 in
Thickness of two stacked coins: 3 mm = 0.1181102362 in
Width of a smartphone screen: 150 mm = 5.905511811 in
Typical screw diameter (M4.5): 4.5 mm = 0.1771653543 in

Common Mistakes to Avoid

Confusing similar units: confusing nautical miles with regular miles, or yards with meters.
Decimal errors: moving the decimal point the wrong way (e.g., 100 cm = 1 m, not 10 m).
Approximation: assuming an inch is exactly 2.5 cm (it's 2.54 cm).

Pro Tips

Use 'approx' for mental math: 1 km is roughly 0.6 miles (or 2/3 for quick estimates).
Visualize: A meter is about a guitar length; an inch is a thumb width.
Ruler check: Most rulers show cm and inches together—great for quick checks.

What is a Millimeter?

The millimeter (mm) is a metric unit of length equal to one-thousandth of a meter (0.001 m). It is a standard unit in the International System of Units (SI).

Millimeters are used for precision engineering, manufacturing dimensions, rainfall measurement, and paper sizes (ISO 216). It represents small scale accuracy.

What is a Inch?

The inch (in) is a unit of length in the Imperial and US customary systems. Historically defined as the width of a thumb or three barleycorns, it is now exactly defined as 25.4 millimeters (0.0254 meters) since 1959.

Inches are widely used in the US, UK, and Canada for short lengths. Common uses include screen sizes (TVs, monitors), pipe diameters, and paper sizes.

Millimeters → Inches

Millimeters to Inches Formula