Millimetres to inches as a decimal and as a fraction.
How to turn millimetres into inches and then into the nearest eighth, sixteenth or sixty-fourth of an inch, with how far off each fraction is.
By Suraj Kumar3 min read
Drawings and parts are often in millimetres while tools and timber are marked in fractions of an inch. Here is how to go between them.
First, the decimal.
An inch is exactly 25.4 mm, so 10 mm is 10 ÷ 25.4 = about 0.3937 inches.
Then the nearest fraction.
Multiply by the bottom you want and round: 0.3937 × 16 = 6.3, so the nearest sixteenth is 6/16, which is 3/8 inch, under by 0.019 inch. In sixty-fourths it is 25/64, much closer. The converter does this for you and lets you choose eighths to sixty-fourths under More options.
Fractions of an inch to millimetres.
Type the fraction as you would read it: 5/8 in to mm gives exactly 15.875 mm, and 1 3/16 in is exactly 30.1625 mm.
Further reading
Topics: mm to inches · mm to inches fraction · millimeters to inches · inches to mm · decimal to inch fraction · drill size conversion
A little less theory. A little more doing.
Try it on your own terms, with a free browser tool.
Try the tool