Inches ↔ Millimeters (mm) Converter
Convert between inches and millimeters instantly
📚 Inches ↔ Millimeters Conversion Details
Inches to Millimeters Formula
To convert inches to millimeters, multiply the inches by 25.4.
Millimeters to Inches Formula
To convert millimeters to inches, divide the millimeters by 25.4.
Conversion Factor
1 inch = 25.4 millimeters exactly
1 millimeter = 0.0393701 inches
This conversion factor is exact and internationally standardized.
Common Uses
- Engineering drawings
- Machinery parts
- Electronic components
- Jewelry measurements
- Precision tools
📏 How This Converter Works
This is a bidirectional converter that works in real-time:
- Inches → Millimeters: When you type in the inches field, the millimeters field automatically updates
- Millimeters → Inches: When you type in the millimeters field, the inches field automatically updates
- No swapping needed: Both conversions happen simultaneously
- Real-time: Updates happen as you type, no button clicks required
mm = inches × 25.4
inches = mm ÷ 25.4
// Example 1: Type "2" in inches
mm = 2 × 25.4 = 50.8
// Example 2: Type "100" in millimeters
inches = 100 ÷ 25.4 = 3.93701
📊 Conversion Table
| Inches | Millimeters | Common Fraction |
|---|---|---|
| 1/16" | 1.5875 mm | 0.0625" |
| 1/8" | 3.175 mm | 0.125" |
| 1/4" | 6.35 mm | 0.25" |
| 1/2" | 12.7 mm | 0.5" |
| 1" | 25.4 mm | 1.0" |
| 2" | 50.8 mm | 2.0" |
❓ Frequently Asked Questions
A: There are exactly 25.4 millimeters in one inch.
A: This conversion factor was internationally standardized in 1959. 1 inch is defined as exactly 25.4 millimeters.
A: This converter provides exact calculations using the exact conversion factor of 25.4.
A: Common uses include engineering, machining, electronics, woodworking, and any precision work where metric measurements are required.