12 inches is equal to 304.8 millimeters.
To convert inches to millimeters, you multiply the inch value by 25.4 because one inch equals exactly 25.4 millimeters. So, 12 inches times 25.4 gives the result in millimeters.
Conversion Tool
Result in mm:
Conversion Formula
The formula to convert inches to millimeters is:
millimeters = inches × 25.4
This works because one inch is internationally defined as exactly 25.4 millimeters. Multiplying the number of inches by 25.4 scales the length to millimeters.
For example, converting 12 inches:
- Take the inch value: 12
- Multiply by 25.4: 12 × 25.4 = 304.8
- The result is 304.8 millimeters
Conversion Example
- Convert 5 inches to mm:
- Start with 5 inches
- Multiply by 25.4: 5 × 25.4 = 127
- 5 inches equals 127 millimeters
- Convert 0.75 inches to mm:
- Begin with 0.75 inches
- Multiply by 25.4: 0.75 × 25.4 = 19.05
- Result: 19.05 millimeters
- Convert 20 inches to mm:
- Value is 20 inches
- Multiply by 25.4: 20 × 25.4 = 508
- 20 inches equals 508 millimeters
- Convert 3.5 inches to mm:
- Start with 3.5 inches
- Multiply by 25.4: 3.5 × 25.4 = 88.9
- Equals 88.9 millimeters
Conversion Chart
| Inches | Millimeters (mm) |
|---|---|
| -13.0 | -330.2 |
| -9.0 | -228.6 |
| -5.0 | -127.0 |
| -1.0 | -25.4 |
| 0.0 | 0.0 |
| 4.0 | 101.6 |
| 8.0 | 203.2 |
| 12.0 | 304.8 |
| 16.0 | 406.4 |
| 20.0 | 508.0 |
| 24.0 | 609.6 |
| 28.0 | 711.2 |
| 32.0 | 812.8 |
| 37.0 | 939.8 |
This chart shows a list of inch values in the left column and their equivalent millimeter values in the right column. Use the chart to quickly look up conversions without calculating manually.
Related Conversion Questions
- How many millimeters are 12 inches exactly?
- What is the mm equivalent for 12 inches in construction measurements?
- Is 12 inches equal to 300 mm or more?
- How do I convert 12 inches to millimeters quickly?
- What’s the difference between 12 inches and 12 inches in mm?
- Can 12 inches be accurately converted to millimeters without rounding?
- Why does 12 inches equal 304.8 mm and not 300 mm?
Conversion Definitions
Inches: An inch is a unit of length in the imperial and US customary systems, equal to 1/12 of a foot or 2.54 centimeters. It is commonly used in the United States, Canada, and the UK for measuring small distances or objects like screen sizes, paper dimensions, and body measurements.
Millimeters: A millimeter is a metric unit of length equal to one-thousandth of a meter. It is used worldwide for precise measurements in engineering, manufacturing, and everyday measurements where small distances matter, such as thickness, height, and width of objects.
Conversion FAQs
Can I convert 12 inches to millimeters using a simple calculator?
Yes, converting 12 inches to millimeters is straightforward. Multiply 12 by 25.4, the exact millimeter length of one inch. Simple calculators, smartphones, or online tools can perform this multiplication fast, giving you 304.8 mm.
Why is one inch equal to 25.4 millimeters?
One inch equals 25.4 millimeters because in 1959, an international agreement fixed the inch definition to exactly 25.4 mm to standardize measurements worldwide. This prevents discrepancies between imperial and metric systems, ensuring consistency in manufacturing and science.
Is the conversion from inches to millimeters exact or approximate?
The conversion from inches to millimeters is exact because one inch is defined as exactly 25.4 mm. There is no approximation involved, so any conversion using this factor will be precise as long as calculations are done properly.
How does temperature affect the inch to millimeter conversion?
Temperature can cause materials to expand or contract, slightly changing actual lengths measured in inches or millimeters. However, the conversion factor itself (25.4 mm per inch) remains constant and unaffected by temperature changes since it’s a defined standard.
Are there devices that measure inches and millimeters simultaneously?
Yes, many measuring tools like calipers and rulers have dual scales showing both inches and millimeters. These devices allow quick visual conversions and measurements without calculation, useful in workshops and engineering fields.