Every fractional, number (gauge), letter, and metric drill bit — with decimal-inch and millimetre equivalents in one sorted list. Enter any size and it finds the closest bit in every system, with the over/undersize gap so you know if it'll do.
"Oversize" means the bit cuts a hole bigger than your target; "undersize" cuts smaller. For a hole that must fit a pin or bolt, pick the closest bit that isn't oversize.
| Decimal inch ▲ | Size | Type | mm |
|---|
Sorted smallest to largest by default — tap any header to re-sort. Number and letter sizes are the ANSI/ASME B94.11M standard values; fractional and metric are exact conversions.
Beyond fractional bits (1/16", 1/8"…), machinists use two finer gauge systems. Number (or "wire gauge") bits run #1 (0.228") down to #80 (0.0135") — bigger number, smaller bit. Letter bits pick up above the numbers, A (0.234") through Z (0.413"). Together they fill the gaps between fractional sizes so you can hit almost any diameter.
5mm is 0.1969". The closest bit is a #9 (0.1960") at just 0.02 mm undersize, or a 13/64" (0.2031") at 0.16 mm oversize. Use the finder above for any size.
A #7 is 0.201" (5.11 mm). It's one of the most-used bits because it's the tap drill for a 1/4"-20 thread — see the tap & drill chart for the full set.
Usually yes for clearance holes, where a little play doesn't matter. For a press fit, dowel pin, or tap drill, the small differences do matter — check the gap in the finder and stay on the side (over or under) that your job needs.