Converting inches to millimeters should be simple. Enter the inch value—decimal or fraction—and get the result in mm instantly. This is a free online tool, no sign‑up needed, easy to use on mobile or desktop. Perfect for students, builders, and everyday measurements.
Inches ⟷ Millimeters
Editable on both sides. Left accepts decimal or fraction inches.
Inch ↔ MM Converter
Inches (decimal or fraction)
Millimeters (mm)
Other Converted Values
How to convert inches to millimeters (Inches to mm)
- Core formula: mm = inches × 25.4
- Why 25.4? By definition, 1 inch equals exactly 25.4 millimeters.
Examples:
- 1 inch in mm = 25.4 mm
- 3 inch in mm = 76.2 mm
- 4 inch in mm = 101.6 mm
- 6 inch in mm = 152.4 mm
Tip: When starting from a fraction (e.g., 3/8″), first convert to decimal (3 ÷ 8 = 0.375) or let the calculator accept the fraction directly, then multiply by 25.4.
Quick reference table
| Inches | Millimeters |
|---|---|
| 1″ | 25.4 mm |
| 1/2″ | 12.7 mm |
| 3/4″ | 19.05 mm |
| 1 1/4″ | 31.75 mm |
| 2″ | 50.8 mm |
| 3″ | 76.2 mm |
| 4″ | 101.6 mm |
| 5″ | 127 mm |
| 6″ | 152.4 mm |
Use the converter above for any value—decimals or mixed fractions.
Common inches in mm conversions users search
- 1 inch in mm = 25.4 mm
- 3 inch in mm = 76.2 mm
- 4 inch in mm = 101.6 mm
- 6 inches in mm = 152.4 mm
- 1/2 inch to mm conversion = 12.7 mm
- 1 1/4 inch to mm = 31.75 mm
- 3 3/8 inch to mm = 85.725 mm
- 5 5/8 inches to mm = 142.875 mm
- 8 5/8 to mm = 219.075 mm
- 38 inches in mm = 965.2 mm
Note: Fraction results are exact to 3 decimal places here; the calculator shows higher precision when needed.
Reverse: millimeters to inches
Need inch in mm and mm back to inches? Use the inverse:
- inches = mm ÷ 25.4
The calculator also shows a fraction approximation (nearest 1/64″) for tape‑friendly results.
When to use decimal vs fraction
- Decimal inches and mm are best for CAD, CNC, 3D printing, and manufacturing specs.
- Fraction inches are better for on‑site measuring with a tape or ruler.
The converter handles both: type 1.75 or 1 3/4 and get clean millimeters.
FAQ: Inches to MM
1 inch = 25.4 millimeters (exact).
Multiply by 25.4. Example: 2.5″ × 25.4 = 63.5 mm.
Yes. Enter 5/8, 1 3/4, or even negatives like -2 1/8; the tool parses them and converts to mm.
12.7 mm.
31.75 mm.
85.725 mm.
142.875 mm.
219.075 mm.
Why this converter?
- Accepts both decimal and fraction inches
- Outputs precise millimeters instantly
- Also shows helpful context (cm, m, feet, yards) without clutter
- Clean layout that mirrors how builders, makers, and engineers work
Bookmark this page for the next time inch and mm need to meet fast.