Inch Fraction Calculator
Tape-measure fractions to decimal and millimeters, or any measurement back to the nearest fraction.
Common fractions, decimals and millimeters
1/16 = 0.0625" = 1.588 mm. 1/8 = 0.125" = 3.175 mm. 1/4 = 0.25" = 6.35 mm. 3/8 = 0.375" = 9.525 mm. 1/2 = 0.5" = 12.7 mm. 5/8 = 0.625" = 15.875 mm. 3/4 = 0.75" = 19.05 mm. 7/8 = 0.875" = 22.225 mm. One full inch is exactly 25.4 mm.
Working between systems
Most tape measures resolve to 1/16 inch, which is about 1.6 mm, so converting a metric plan to sixteenths can be off by up to 0.8 mm on every mark. The rounding error output shows exactly how much you're giving up; switch to 1/32 precision when it matters, or keep the whole job in one system when it really matters.