Inches to MM Converter — Inch to Millimeter Calculator
Convert inches to millimeters (mm) and mm to inches instantly. Each inch equivalent to 25.4 mm — for engineering, 3D printing, woodworking, and metric ↔ imperial projects in the USA, UK, and Canada.
Convert Inches to Millimeters
Live conversion as you type. 1 in × 25.4 = 25.4 mm (exact international inch)
Inches to Millimeters Conversion Chart
Common inch values with mm and cm. Click a row to load the converter.
| Inches (in) | Millimeters (mm) | Centimeters (cm) | Notes |
|---|
Fractional Inches to Millimeters
Standard US fractional inch sizes used in woodworking, pipes, and wrenches.
| Fraction | Decimal (in) | Millimeters (mm) |
|---|
Everyday Measurements in Inches & MM
Screens, paper, bolts, and common objects — useful for USA, UK & Canada.
| Item | Inches | Millimeters |
|---|
Batch Inches to Millimeters
Enter inch or mm values — one per line or comma-separated.
Convert to All Length Units
From inches or millimeters to cm, feet, yards, and meters.
Length Conversion Formulas
NIST international inch — exact factors used by this calculator.
How to Convert Inches to Millimeters
The international inch is defined as exactly 25.4 millimeters (since 1959, NIST standard). To convert inches to mm, multiply by 25.4: 2 in × 25.4 = 50.8 mm. To convert millimeters to inches, divide by 25.4: 50.8 mm ÷ 25.4 = 2 in.
In the United States, blueprints, lumber, and screen sizes often use inches while metric tools read millimeters. The UK and Canada officially use metric, but imperial inches still appear on imports, fasteners, and DIY guides. This converter bridges both systems for machining tolerances, 3D printer settings, and tape-measure readings.
Inches to millimeters chart
| Inches | Millimeters | Common use |
|---|---|---|
| ⅛ in (0.125) | 3.175 mm | Small drill bit |
| ¼ in (0.25) | 6.35 mm | Hardware, fittings |
| ½ in (0.5) | 12.7 mm | Pipes, lumber thickness |
| 1 in | 25.4 mm | Base inch unit |
| 6 in | 152.4 mm | Phone / tablet screen |
| 12 in | 304.8 mm | One foot |
| 36 in | 914.4 mm | One yard |
Inches vs millimeters — USA, UK & Canada
- USA: Tape measures show inches and feet; CNC and 3D printing often need mm input.
- UK: Road signs use metric; home improvement still mixes imperial inches with mm wrenches.
- Canada: Building codes are metric; US lumber and tools may list inches only.
Related length converters
Inches to MM FAQ
How many millimeters are in 1 inch?
1 inch is equivalent to 25.4 millimeters. This is the international standard inch definition.
How do I convert 2 inches to mm?
You have to multiply 2 in and 25.4. And the result is 50.8 mm. Multiply any inch value by 25.4 for millimeters.
How many inches is 100 mm?
100 mm ÷ 25.4 ≈ 3.937 in. Use the swap button on this page for instant reverse conversion.
What is ¼ inch in millimeters?
¼ inch = 6.35 mm (0.25 × 25.4). See the Fractions tab for more standard sizes.
Is the inch to mm conversion exact?
Yes. Since 1959, 1 in = 25.4 mm by definition — not an approximation. Rounding only affects how many decimal places you display.
How many mm is 12 inches?
12 in × 25.4 = 304.8 mm — the same as one foot.
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2026-06-05 11:00:37
Taylor Bennett