Decimal Equivalent Chart

Every inch fraction from 1/64" to 1", paired with its exact decimal value and millimeter equivalent. This is the master reference behind most of the calculators on this site: read across any row to move between fraction, decimal, and metric, or scan the decimal column to find the closest fraction to a measurement you already have.

The table below uses the same 64ths progression as a standard machinist scale, so every row corresponds to a mark you can actually find on a ruler, a fractional drill index, or a stock rack label.

Start from whichever column you already have. If you know the fraction (say, a bit stamped "3/8\""), read across to get 0.375" and 9.525 mm. If you know a decimal measurement from a caliper or a drawing, scan the decimal column for the closest value and read left to the matching fraction. If you have a millimeter spec, scan the mm column instead.

For an interactive version that accepts any decimal value, not just the rows shown here, use the decimal to inches calculator on the homepage. To convert a single inch fraction to millimeters, use the Inch Fraction to MM Converter. For drill bit sizing specifically, see the drill size chart.

Looking up a single value instead of the whole table? Each common inch fraction and decimal below has its own quick-answer page with a mini calculator and worked example.