inches to mm conversion
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Common Inches to MM Conversions
| Inches | Fraction | Millimeters |
|---|---|---|
| 0.25 | 1/4 | 6.35 mm |
| 0.5 | 1/2 | 12.7 mm |
| 0.75 | 3/4 | 19.05 mm |
| 1 | 1 | 25.4 mm |
| 1.25 | 1 1/4 | 31.75 mm |
| 1.5 | 1 1/2 | 38.1 mm |
| 1.75 | 1 3/4 | 44.45 mm |
| 2 | 2 | 50.8 mm |
| 2.25 | 2 1/4 | 57.15 mm |
| 2.5 | 2 1/2 | 63.5 mm |
| 2.75 | 2 3/4 | 69.85 mm |
| 3 | 3 | 76.2 mm |
| 3.5 | 3 1/2 | 88.9 mm |
| 4 | 4 | 101.6 mm |
| 4.5 | 4 1/2 | 114.3 mm |
| 5 | 5 | 127 mm |
| 5.5 | 5 1/2 | 139.7 mm |
| 6 | 6 | 152.4 mm |
How to Convert Inches to Millimeters
Converting inches to millimeters is straightforward once you understand the basic relationship between these two units of measurement. Whether you're working on engineering projects, crafting, or simply need precise measurements, this guide will help you master inches to mm conversion.
The Golden Rule
1 inch = 25.4 millimeters (exactly)
This conversion factor is precise and universally accepted worldwide.
Step-by-Step Conversion Process
Method 1: Simple Multiplication
- Step 1: Take your measurement in inches
- Step 2: Multiply by 25.4
- Step 3: The result is in millimeters
Method 2: Using Fractions
- Step 1: Convert fraction to decimal
- Step 2: Multiply by 25.4
- Step 3: Round to desired precision
Common Conversion Examples
1/8 inch to mm:
0.125 × 25.4 = 3.175 mm
1/4 inch to mm:
0.25 × 25.4 = 6.35 mm
3/8 inch to mm:
0.375 × 25.4 = 9.525 mm
1/2 inch to mm:
0.5 × 25.4 = 12.7 mm
3/4 inch to mm:
0.75 × 25.4 = 19.05 mm
1 inch to mm:
1 × 25.4 = 25.4 mm
Why Use Inches to MM Conversion?
Imperial System (Inches)
- • Common in the United States
- • Used in construction and carpentry
- • Traditional measurement system
- • Based on 12 inches = 1 foot
Metric System (Millimeters)
- • Used worldwide as standard
- • Preferred in engineering and science
- • Decimal-based for easy calculations
- • More precise for small measurements
Tips for Accurate Conversion
- Always use 25.4 as the exact conversion factor - this is the internationally accepted standard
- Round appropriately - for most applications, 2-3 decimal places is sufficient
- Double-check your calculations - especially for critical measurements
- Consider your measurement tools - ensure they match the precision you need
- Use our calculator above for instant, accurate conversions
Practical Applications
Engineering
Precise measurements for mechanical parts, blueprints, and technical drawings
Crafting
Converting pattern measurements, jewelry making, and detailed craft work
Construction
Material specifications, hardware sizing, and architectural measurements
Frequently Asked Questions
To convert 2.5 inches to mm, multiply 2.5 by 25.4. The result is 63.5 millimeters. This is one of the most common conversions used in various applications.
The exact conversion factor is 1 inch = 25.4 millimeters. This is defined by international standards and is precise, not an approximation.
Our converter uses the exact conversion factor of 25.4 and provides results accurate to 4 decimal places, which is suitable for most professional and personal applications.
Yes! First convert the fraction to a decimal (e.g., 3/4 = 0.75), then multiply by 25.4. For example, 3/4 inch = 0.75 × 25.4 = 19.05 mm.
For quick estimates, you can multiply inches by 25. This gives you a close approximation. For example, 2 inches ≈ 50 mm (actual: 50.8 mm). For precision work, always use the exact factor of 25.4.