Samantha Nicole1 inch is equal to 25.4 millimetres.
The inch and millimetre are both units used for measuring length or distance. Because 1 inch is internationally defined as exactly 25.4 millimetres, the conversion between these two units is direct and precise, making it easy to switch between imperial and metric measurements.
Conversion Tool
Result in millimetres:
Conversion Formula
The conversion from inch to millimetres uses a fixed ratio. Exactly, 1 inch equals 25.4 millimetres. This comes from international agreement, ensuring consistency across measurements worldwide. To convert inches to millimetres, multiply the inch value by 25.4.
Formula:
Millimetres = Inches × 25.4
Example calculation:
For 1 inch, multiply 1 × 25.4 = 25.4 millimetres. This means every inch has 25.4 millimetres inside it.
Conversion Example
- Convert 3 inches to millimetres:
- Multiply 3 by 25.4
- 3 × 25.4 = 76.2 millimetres
- So, 3 inches equals 76.2 millimetres.
- Convert 0.5 inches to millimetres:
- Multiply 0.5 by 25.4
- 0.5 × 25.4 = 12.7 millimetres
- Therefore, 0.5 inch equals 12.7 millimetres.
- Convert 7.25 inches to millimetres:
- Multiply 7.25 by 25.4
- 7.25 × 25.4 = 184.15 millimetres
- This means 7.25 inches equals 184.15 millimetres.
- Convert 10 inches to millimetres:
- Multiply 10 by 25.4
- 10 × 25.4 = 254 millimetres
- So, 10 inches is equal to 254 millimetres.
Conversion Chart
This chart shows values from -24.0 to 26.0 inches, converted into millimetres. To find the millimetre equivalent, multiply the inch value by 25.4. Negative values represent lengths measured in the opposite direction or below a reference point.
| Inches | Millimetres |
|---|---|
| -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 |
| 4.0 | 101.6 |
| 6.0 | 152.4 |
| 8.0 | 203.2 |
| 10.0 | 254.0 |
| 12.0 | 304.8 |
| 14.0 | 355.6 |
| 16.0 | 406.4 |
| 18.0 | 457.2 |
| 20.0 | 508.0 |
| 22.0 | 558.8 |
| 24.0 | 609.6 |
| 26.0 | 660.4 |
Related Conversion Questions
- How many millimetres are in 1 inch exactly?
- Is 1 inch always equal to 25.4 millimetres?
- What is the formula to convert 1 inch into millimetres?
- Can I convert 1 inch to millimetres without a calculator?
- Why does 1 inch equal 25.4 millimetres and not another number?
- How precise is the conversion from 1 inch to millimetres?
- What is 1 inch in millimetres rounded to two decimal places?
Conversion Definitions
Inch: An inch is a unit of length in the imperial system, used mainly in the United States, Canada, and the UK. It equals exactly 2.54 centimetres or 25.4 millimetres. Inches are subdivided into fractions like halves, quarters, and eighths for finer measurements.
Millimetres: The millimetre is a metric unit of length equal to one thousandth of a metre. It’s widely used around the world for precise measurements, especially in engineering, manufacturing, and science. One millimetre equals 0.03937 inches approximately.
Conversion FAQs
Why is the inch defined as exactly 25.4 millimetres?
The inch was standardized internationally in 1959 by several countries including the US and UK. Before that, inch definitions varied slightly. Fixing it at 25.4 millimetres ensures consistent measurement across different systems and industries, eliminating confusion and improving accuracy.
Can I use the conversion factor 25.4 for any length in inches?
Yes, the factor 25.4 applies to any length measured in inches, whether it’s very small or very large. Since the inch is defined exactly as 25.4 millimetres, multiplying by this factor always gives the correct millimetre equivalent, no matter the size.
What causes small errors in inch to millimetre conversion?
Errors arise mainly from rounding off decimal places or using approximated values instead of the exact 25.4. Also, measuring tools may introduce inaccuracies. Using the exact factor and precise instruments minimizes these mistakes, producing accurate results.
Are there other units related between inch and millimetre?
Yes, inches relate to centimetres (1 inch = 2.54 cm) and micrometres (1 inch = 25400 micrometres). Millimetres fit into this metric chain, making conversion between units straightforward when needed.
How do I convert millimetres back to inches?
To convert millimetres to inches, divide the millimetre value by 25.4. For example, 50.8 millimetres divided by 25.4 equals 2 inches. This reverses the inch to millimetre conversion accurately.
