Millimeters (mm) and inches are two of the most widely used measurement units globally. While the metric system (mm) is standard in most countries, inches remain prevalent in the United States, Canada, and the UK—especially in construction, woodworking, and manufacturing.
Our mm to inches ruler tool helps you:
- Convert measurements instantly
- Understand the exact fraction/decimal equivalents
- Save time on manual calculations
Quick Fact:
*1 inch = 25.4 millimeters exactly* (international standard since 1959).
MM to Inches Converter
MM to Inches Conversion Chart
| Millimeters (mm) | Inches (Decimal) | Inches (Fraction) |
|---|---|---|
| 1 mm | 0.0394" | 1/32" |
| 5 mm | 0.1969" | 13/64" |
| 10 mm | 0.3937" | 25/64" |
| 25.4 mm | 1.0000" | 1" |
| 50 mm | 1.9685" | 2" |
| 100 mm | 3.9370" | 4" |
| 300 mm | 11.8110" | 11 13/16" |
Note: Fractional inches are rounded to nearest 1/64"
How to Convert Manually
Millimeters → Inches
Divide by 25.4
Example: 50 mm ÷ 25.4 = 1.9685 inches
Inches → Millimeters
Multiply by 25.4
Example: 2 inches × 25.4 = 50.8 mm
Why 25.4?
The international yard and pound agreement (1959) standardized 1 inch as exactly 25.4 millimeters.
How big is 4mm
4 millimeters is approximately 0.1575 inches in decimal form, or just over 5/32 inches in fractional form. It’s slightly thicker than a standard pencil lead or about the thickness of two stacked credit cards.
11 mm to inches
11 millimeters is approximately 0.4331 inches in decimal form, or just under 7/16 inches in fractional form. It’s about the width of a common AAA battery or slightly wider than the short side of a USB plug.
3mm in inches
3 millimeters is approximately 0.1181 inches in decimal form, or just under 1/8 inch in fractional terms. It’s about the thickness of two stacked U.S. pennies.
How big is 4mm on a ruler
4 millimeters (mm) is the fourth small mark on a metric ruler, just before 0.5 cm. On an inch ruler, it’s about 0.157 inches, a bit more than 5/32″.
14 mm to inches
14 millimeters is about 0.551 inches, which is just over 9/16 of an inch.
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