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Inch ↔ mm Converter
To convert inches to millimeters, multiply by 25.4. To convert millimeters to inches, divide by 25.4.
Interactive Converter (Cron-style options layout)
Pick a mode, then enter a value
Rounding decimals
Result
Mode
inch → mm
Expression
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Quick Conversion Formula
Same content, Cron-like box
millimeters = inches × 25.4
inches = millimeters ÷ 25.4
1 inch = 25.4 mm (internationally agreed conversion factor).
Common Inch to mm Conversions
Reference table
| Inches (in) | Millimeters (mm) |
|---|---|
| 1/16 | 1.5875 |
| 1/8 | 3.1750 |
| 1/4 | 6.3500 |
| 1/2 | 12.7000 |
| 1 | 25.4000 |
| 2 | 50.8000 |
Tip: 1 inch = 25.4 mm, so 4 inches ≈ 101.6 mm.
Real-World Examples
Practical understanding
- A 1/2 inch screw diameter is about 12.7 mm.
- A 2-inch pipe is about 50.8 mm.
- 1 inch is exactly 25.4 mm (common in tools/hardware).
Common Mistakes
Avoid errors
Most common mistake: dividing by 25.4 when converting inches → mm (you should multiply).
FAQ
Quick answers
Is 1 mm equal to 1 inch? No. 1 inch equals 25.4 mm.
Why 25.4? It is the internationally agreed conversion factor.
How many mm is 3 inches? 3 × 25.4 = 76.2 mm.
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