Inches to Millimeters Converter
Convert inches to millimeters. The formula used here is 1 inch = 25.4 millimeters. The formula is mm = in × 25.4; 1 in is 25.4 mm.
A US customary and imperial length unit equal to 1/12 of a foot.
A metric length unit equal to one thousandth of a meter.
Start with your value in inches, then apply the formula below. It stays visible so you can catch rounding mistakes instead of just copying the output.
When the converted length drives a cut, fit, clearance, or route estimate, decide whether to round to the nearest mark, round up for safety, or keep decimals for documentation.
Many length factors are exact by definition, but practical measurements still depend on rulers, survey tools, tolerances, and how the result will be used. This page displays converted values with up to 4 decimal places by default.
| Inches | Millimeters |
|---|---|
| 1 in | 25.4 mm |
| 6 in | 152.4 mm |
| 12 in | 304.8 mm |
| 24 in | 609.6 mm |
| 36 in | 914.4 mm |
Useful for checking construction and DIY measurements. Use the same formula with your exact input if the measurement needs to be documented.
Useful for travel, mapping, or athletics distances. Use the same formula with your exact input if the measurement needs to be documented.
Useful for product dimensions and classroom conversions. Use the same formula with your exact input if the measurement needs to be documented.
How do I convert inches to millimeters?
Enter the value in inches and apply mm = in × 25.4. Round the millimeters result after the conversion, not before.
What is 1 inch in millimeters?
1 in equals 25.4 mm with the current rounding setting. Keep more decimal places when the result feeds another calculation.
What is 6 in in mm?
6 in is 152.4 mm. It appears in the lookup table so you can compare it with nearby amounts.
Can I convert millimeters back to inches?
Yes. Use the reverse Millimeters to Inches converter if you need to go the other direction.
How accurate is this inches to millimeters conversion?
The calculator runs the formula in your browser and rounds results to 4 decimal places by default. Many length factors are exact by definition, but practical measurements still depend on rulers, survey tools, tolerances, and how the result will be used.