01 inch equals 25.4 millimeters (mm).
An inch is converted to millimeters by multiplying the inch value by 25.4, because 1 inch is exactly 25.4 mm by international agreement. This conversion allows for easy switching between the imperial and metric measuring systems.
Conversion Tool
Result in mm:
Conversion Formula
The formula to convert inches to millimeters is simple: multiply the inch value by 25.4. This works because one inch is agreed to be exactly 25.4 millimeters in length.
Mathematically, it looks like this:
millimeters = inches × 25.4
For example, for 1 inch:
- millimeters = 1 × 25.4
- millimeters = 25.4 mm
This calculation converts a length measured in inches directly to millimeters, which is a metric unit.
Conversion Example
- Convert 5 inches to mm:
- Multiply 5 by 25.4
- 5 × 25.4 = 127 mm
- So 5 inches equals 127 millimeters
- Convert 0.5 inches to mm:
- Multiply 0.5 by 25.4
- 0.5 × 25.4 = 12.7 mm
- Therefore, 0.5 inches equals 12.7 millimeters
- Convert 12.75 inches to mm:
- Multiply 12.75 by 25.4
- 12.75 × 25.4 = 323.85 mm
- Thus, 12.75 inches equals 323.85 millimeters
Conversion Chart
The chart below shows conversion from inches to millimeters, covering values from -24.0 to 26.0 inches. To use it, find the inch value in the left column and read across to see the equivalent millimeter value.
| Inches | Millimeters (mm) |
|---|---|
| -24.0 | -609.60 |
| -20.0 | -508.00 |
| -16.0 | -406.40 |
| -12.0 | -304.80 |
| -8.0 | -203.20 |
| -4.0 | -101.60 |
| 0.0 | 0.00 |
| 4.0 | 101.60 |
| 8.0 | 203.20 |
| 12.0 | 304.80 |
| 16.0 | 406.40 |
| 20.0 | 508.00 |
| 24.0 | 609.60 |
| 26.0 | 660.40 |
Related Conversion Questions
- How many millimeters are in 1 inch exactly?
- What is the precise conversion factor from inch to mm for 1 inch?
- Can I convert 1 inch to millimeters without rounding?
- What is 1 inch in mm for engineering measurements?
- How do I convert 1 inch to millimeters in JavaScript?
- Is 1 inch always equal to 25.4 mm in all countries?
- Why is 1 inch defined as 25.4 millimeters?
Conversion Definitions
Inch: An inch is a unit of length in the imperial and US customary systems, equal to 1/12 of a foot or 1/36 of a yard. It is defined exactly as 25.4 millimeters by international agreement. Inches are used mainly in the United States, Canada, and the UK for measuring small distances.
Millimeter (mm): A millimeter is a metric unit of length equal to one thousandth of a meter (0.001 m). It is used globally for precise measurements in engineering, manufacturing, and everyday measurements. Millimeters provide a finer scale than centimeters or meters for small lengths.
Conversion FAQs
Is the inch to millimeter conversion exact or approximate?
The conversion from inch to millimeter is exact. By international agreement, one inch equals exactly 25.4 millimeters. This standard has been used since 1959 and ensures consistent measurements worldwide.
Why is 1 inch defined as 25.4 millimeters?
The inch was standardized as 25.4 millimeters to harmonize measurements between imperial and metric systems. Before this, inches varied in length depending on country or context. This exact value was agreed on for engineering and trade consistency.
Can millimeters be used instead of inches in all cases?
Millimeters can replace inches for many measurements, but not always. In countries using the imperial system or for legacy tools, inches remain standard. However, scientific and international settings often prefer millimeters for precision and metric compatibility.
How to convert fractions of an inch to millimeters?
Fractions of an inch are first converted to decimals, then multiplied by 25.4. For example, 1/2 inch equals 0.5 inches, so 0.5 × 25.4 = 12.7 mm. This method works for any fractional inch measurement.
Does temperature affect inch to mm conversion?
The inch to millimeter conversion itself does not change with temperature, because it is a fixed mathematical ratio. However, physical materials can expand or contract with temperature, so actual lengths may vary slightly in practice.