1 inch is equal to 25.4 millimeters.
To convert inches to millimeters, you multiply the inch value by 25.4, because there are exactly 25.4 millimeters in an inch. This makes it easy to switch between these units of length.
Conversion Tool
Result in mm:
Conversion Formula
The formula to convert inches to millimeters is:
millimeters = inches × 25.4
This works because one inch exactly equals 25.4 millimeters. So multiplying any inch value by 25.4 gives the equivalent length in millimeters.
For example, to convert 1 inch to millimeters:
- Start with the inch value: 1
- Multiply by 25.4: 1 × 25.4 = 25.4
- The result: 25.4 mm
Conversion Example
- Convert 5 inches to mm:
- Multiply 5 × 25.4
- 5 × 25.4 = 127 mm
- So, 5 inches equals 127 millimeters
- Convert 0.75 inches to mm:
- Multiply 0.75 × 25.4
- 0.75 × 25.4 = 19.05 mm
- Therefore, 0.75 inches is 19.05 millimeters
- Convert 12.5 inches to mm:
- Multiply 12.5 × 25.4
- 12.5 × 25.4 = 317.5 mm
- Hence, 12.5 inches equals 317.5 millimeters
- Convert -3 inches to mm:
- Multiply -3 × 25.4
- -3 × 25.4 = -76.2 mm
- Negative length means direction or position, so -3 inches equals -76.2 millimeters
Conversion Chart
| Inches | Millimeters (mm) |
|---|---|
| -24.0 | -609.6 |
| -20.0 | -508.0 |
| -16.0 | -406.4 |
| -12.0 | -304.8 |
| -8.0 | -203.2 |
| -4.0 | -101.6 |
| 0.0 | 0.0 |
| 2.0 | 50.8 |
| 6.0 | 152.4 |
| 10.0 | 254.0 |
| 14.0 | 355.6 |
| 18.0 | 457.2 |
| 22.0 | 558.8 |
| 26.0 | 660.4 |
This chart helps you quickly see equivalent millimeter values for different inch lengths. Find your inch value on the left, then read across to find the millimeter conversion on the right. Negative values show lengths or distances in opposite direction.
Related Conversion Questions
- How many millimeters equal 1 inch exactly?
- What is the precise millimeter value for one inch conversion?
- Can I convert 1 inch to millimeters without a calculator?
- Is 1 inch more or less than 25 millimeters?
- How does 1 inch compare to 1 millimeter in size?
- How to convert 1 inch to mm in a quick way?
- Why does 1 inch equal 25.4 millimeters?
Conversion Definitions
Inches: An inch is a unit of length used in the United States customary and British imperial systems. Defined as exactly 25.4 millimeters, inches are divided into smaller parts like halves, quarters, and eighths, commonly used in measuring length, height, and width in everyday objects.
Millimeters (mm): A millimeter is a metric unit of length, equal to one thousandth of a meter. It is commonly used worldwide in measuring small distances, thickness, or diameters. Millimeters are part of the metric system, which uses base 10, making conversions easy between units like centimeters and meters.
Conversion FAQs
Is the conversion factor between inches and millimeters exact?
Yes, the conversion factor is exact. One inch is defined as exactly 25.4 millimeters by international agreement. This fixed value ensures consistent conversions worldwide without approximation errors in the base factor.
Why do some tools give slightly different mm values for inches?
Some tools round conversion results differently, or use approximations for the factor 25.4, causing small discrepancies. Others might truncate decimal digits or use less precise calculations. Using the exact 25.4 factor avoids these issues.
Can I use this conversion for very small or very large measurements?
Yes, you can convert inches to millimeters for any size length, whether very small fractions or very large distances. Since both units measure linear distance, the multiplication by 25.4 applies the same way regardless of scale.
Are inches and millimeters used together in measurements?
Sometimes, especially in countries with mixed measurement systems, both units appear on tools or blueprints. This dual usage requires clear conversion between inches and millimeters to avoid errors in manufacturing or construction.
Does negative inch value conversion make sense?
Negative inch values can represent direction or position relative to a reference point. When converting, negative inches convert to negative millimeters, keeping the directional meaning intact in the metric system.