mm to Inches Converter
Convert small lengths between millimetres and inches, with a fraction for tape measures. Type in either side.
About this tool
Uses the exact definition 1 inch = 25.4 mm. The fraction is rounded to the nearest sixteenth of an inch, as marked on most imperial tape measures.
Screw sizes, screen bezels, rainfall and jewellery are measured in millimetres in most of the world but in inches in many product specs and tools. Type a length in millimetres to see inches, centimetres and the nearest tape-measure fraction, or type inches to get millimetres. Both boxes update as you type.
How to use the mm to Inches Converter
- Type a length in millimetres, for example 50.
- Read the inches next to it, and the fraction below.
- Or type inches instead, and the millimetres update.
- Use the fraction to find the mark on an imperial tape measure.
Converting 50 mm and 3/4 inch
50 ÷ 25.4 = 1.969 inches, which is closest to 1 15/16 in on a tape measure. Going the other way, a 3/4-inch pipe is 0.75 × 25.4 = 19.05 mm.
The exact inch
Since 1959 the inch has been exactly 25.4 mm. Divide millimetres by 25.4 to get inches, or multiply inches by 25.4 to get millimetres. Imperial tape measures mark inches in halves, quarters, eighths and sixteenths, so the converter also rounds to the nearest sixteenth (1/16 inch is about 1.59 mm).
Frequently asked questions
How many mm is an inch?
Exactly 25.4 mm.
How many inches is 10 mm?
About 0.394 inches, a little over 3/8 in.
What is 1/8 inch in mm?
3.175 mm.
Is a 6 mm drill bit the same as 1/4 inch?
Close but not the same: 1/4 inch is 6.35 mm.