Convert Inches to Millimeters
Converting inches to millimeters helps when you read a US measurement but need a metric value.
It is useful for tools, product sizes, engineering drawings, and 3D printing.
Quick Answer
1 inch = 25.4 millimeters
Example 1: 2 inches = 2 × 25.4 = 50.8 mm
Example 2: 10 inches = 10 × 25.4 = 254 mm
Conversion Formula
Formula: millimeters = inches × 25.4
This means you multiply the number of inches by 25.4 to get the same length in millimeters.
- Write down the inches value.
- Multiply it by 25.4.
- The result is the length in millimeters.
What Is Inch
An inch is a length unit used mainly in the United States and a few other places.
It is commonly used for everyday measuring and product dimensions.
- Measuring screens like TVs and phones
- DIY projects with rulers and tape measures
- Pipe and bolt sizes in some systems
- Furniture sizes and room planning
- Paper and printing sizes in some regions
What Is Millimeters?
A millimeter is a metric length unit that equals one thousandth of a meter.
It is used worldwide for precise measurements.
- Engineering and mechanical drawings
- 3D printing and model making
- Measuring thickness of materials like metal or plastic
- Small parts like screws, drill bits, and washers
- Medicine and lab measurements for small distances
Real Life Examples
Here are common situations where you may need to convert inches to millimeters.
- A 6 inch phone screen width measurement is 6 × 25.4 = 152.4 mm
- A 1/2 inch drill bit is 0.5 × 25.4 = 12.7 mm
- A 3 inch pipe section length is 3 × 25.4 = 76.2 mm
- A 12 inch ruler is 12 × 25.4 = 304.8 mm
- A 0.25 inch material thickness is 0.25 × 25.4 = 6.35 mm
- A 15 inch laptop screen size is 15 × 25.4 = 381 mm
- A 2.75 inch part on a drawing is 2.75 × 25.4 = 69.85 mm
Quick Tips
- Remember the exact rule, 1 inch = 25.4 mm.
- For a fast estimate, use 1 inch ≈ 25 mm, then adjust a little higher.
- To estimate quickly, multiply by 25, then add 0.4 times the inches.
- If you have a fraction, convert it to decimal first, like 1/8 = 0.125.
- Keep extra decimals for precision, then round at the end.
- Double check units, mm is much smaller than inches, so the number should get bigger.