How to Convert Inches to Millimeters
Converting inches to millimeters multiplies by 25.4 exactly — this is an internationally defined relationship (1 inch = 25.4 mm since 1959). One of the most precise and widely used conversions in engineering and manufacturing.
1.00 Inches = 25.4000 Millimeters
Multiply by 25.4 to get your result.
Step-by-Step
- Start with your value: 1.00 inches
- Multiply by 25.4
- Result: 25.4000 millimeters
Formula: Millimeters = Inches × 25.4
💡 Memory Tip: 1 inch = exactly 25.4 mm. This is one of the few exact, defined conversions. Multiply by 25.4.
Inches to Millimeters Quick Reference
| Inches | Millimeters | Reference |
|---|---|---|
| 1 | 25.4 | 1 inch exactly |
| 0.5 | 12.7 | Half inch |
| 12 | 304.8 | 1 foot |
| 6 | 152.4 | 6 inches |
| 36 | 914.4 | 1 yard |
Understanding Inches and Millimeters
What is a Inches?
An inch (in) is an imperial unit of length equal to exactly 2.54 centimeters, or 1/12 of a foot. Used for screen sizes, pipe diameters, and small-scale measurements.
What is a Millimeters?
A millimeter (mm) is 1/1000 of a meter, or about 0.0394 inches. It is the standard unit for precision measurements in engineering, manufacturing, and medicine.
Learn more about Inches on Wikipedia →
Real-World Applications
Metric and imperial tools use this constantly. A 10mm socket wrench is 0.394 inches, close to 3/8 inch. Pipe fittings, drill bits, and fasteners are specified in both units in hardware stores. Screen bezels are measured in mm; diagonal screen size in inches.
Key Conversion Facts
- 1 inch = 25.4 mm exactly (defined in 1959)
- 1/4 inch = 6.35 mm
- 1/8 inch = 3.175 mm
- 12 inches = 304.8 mm = 1 foot
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Frequently Asked Questions
1 inches equals 25.4000 millimeters.
Millimeters = Inches × 25.4
For 1 inches: 1 gives 25.4000 millimeters.
1 inches = 2.5400 cm.
1 inches = 25.4000 millimeters. This is a standard measurement used in many practical applications including construction, science, and everyday life.
In 1959, English-speaking nations (US, UK, Canada, Australia) redefined the yard as exactly 0.9144 meters, making 1 inch = 0.0254 m = 25.4 mm. This international yard eliminated small discrepancies between national standards.