Why is 1 inch exactly 25.4 mm?

By international agreement (1959), 1 inch is defined as exactly 25.4 mm. This standardizes conversions between imperial (US/UK) and metric systems.

I have a US print spec with 0.75 inch margins. What's that in millimeters?

0.75 inch × 25.4 = 19.05 mm. Use this when applying US print templates to metric international print specs.

My international client needs specifications in centimeters. How do I convert?

Divide mm by 10. Example: 25.4 mm = 2.54 cm (1 inch). This makes it easy to work with metric systems.

Is the conversion always 25.4?

Yes, exactly. Unlike some historical variations, the inch-to-millimeter conversion is legally standardized at 25.4 mm per inch since 1959.

Inch to Millimeter Converter

Enter a value to instantly convert between typography units.

From

Precision4 dp

1 Inch = 25.4 Millimeter

Key Formulas

Point → Pica

pc = pt × 0.0833333

Point → Inch

in = pt × 0.0138889

Pica → Inch

in = pc × 0.166667

Inches are imperial units used primarily in North America; millimeters are metric units used internationally. The exact conversion is 1 inch = 25.4 mm. This is critical for designers and printers working with global clients, translating US print specs to metric international standards.

Last reviewed: 2026-06-11 · see our methodology

Frequently Asked Questions

Real-World Examples

0.5 inch = 12.7 mm. Standard margin width in US documents; translates to just over 1 centimeter in metric.

0.5 in = 12.7 mm

1 inch = 25.4 mm. Full-inch measurements are the metric standard's nearest equivalent for international communication.

1 in = 25.4 mm

2 inches = 50.8 mm. Standard print column width (US trade publishing) equals about 5 centimeters metric.

2 in = 50.8 mm

8.5 inches (US Letter width) = 215.9 mm. Standard paper size conversion for international document preparation.

8.5 in = 215.9 mm

points to picas points to type inches picas to type inches points to mm pixels to points ems to rems

Inch to Millimeter Converter

Key Formulas

Frequently Asked Questions

Real-World Examples

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