Last updated: September 2026
Length conversion
Millimeters to Inches
Useful for hardware, machining, 3D printing, and technical drawings where small metric dimensions need inch values.
Answer
Millimeters to Inches
1 millimeter equals 0.0393700787402 inches. 1 inch equals 25.4 millimeters, so in = mm ÷ 25.4.
in = mm ÷ 25.4
| Millimeters | Inches |
|---|---|
| 1 mm | 0.0393700787402 in |
| 2 mm | 0.0787401574803 in |
| 5 mm | 0.196850393701 in |
| 10 mm | 0.393700787402 in |
| 25 mm | 0.984251968504 in |
| 100 mm | 3.93700787402 in |
Common questions
How many inches are in 1 millimeter?
1 millimeter equals 0.0393700787402 inches. Divide millimeters by 25.4. The formula is in = mm ÷ 25.4.
What is 0.0393700787402 inches in millimeters?
0.0393700787402 inches equals 1 millimeter. 1 inch equals 25.4 millimeters, and 1 ÷ 25.4 inches is 1 millimeter, shown to 12 significant digits.
Calculated from OmniUnit's stored unit factors and shown to 12 significant digits.
1 mm
0.0393700787402 in
in = mm ÷ 25.4
The formula
How to convert millimeters to inches
Apply in = mm ÷ 25.4. For example, 1 mm equals 0.0393700787402 in.
Precision
Accurate constants, readable results
OmniUnit calculates with the full stored conversion factor, then displays up to 12 significant digits.
Common millimeters conversions
| Millimeters | Inches |
|---|---|
| 1 mm | 0.0393700787402 in |
| 2 mm | 0.0787401574803 in |
| 5 mm | 0.196850393701 in |
| 10 mm | 0.393700787402 in |
| 25 mm | 0.984251968504 in |
| 100 mm | 3.93700787402 in |
Related length conversions
Frequently asked questions
How many inches are in 1 millimeter?
One millimeter equals 0.0393700787402 inches. The inch is defined as exactly 25.4 millimeters, so one millimeter is 1 ÷ 25.4 inches, which is 0.0393700787402.
How many millimeters are in 1 inch?
One inch equals exactly 25.4 millimeters, by international definition. To convert inches back to millimeters, use the inches-to-millimeters page, which shows the exact formula and a quick calculator.
How do I convert millimeters to inches without a calculator?
Multiply the millimeters by 0.0394 for a quick estimate — for example, 100 mm is about 3.94 inches. For precise results, use the calculator above or divide the millimeters by 25.4.
Is the millimeter-to-inch conversion exact?
Yes. The inch is defined as exactly 25.4 millimeters, so 1 mm = 0.0393700787402 in is a fixed definition, not a measurement. OmniUnit calculates with the full stored factor for maximum precision.