Drill Size Converter
Enter a drill size in whatever system you have it in, and get the closest equivalent in every other system back — no scrolling a chart.
How the match is found
This tool converts whatever you enter to a decimal inch size, then scans the full number, letter, and 64ths-fraction drill index to find the closest match in each of the other systems — the same underlying dataset as the full Drill Bit Size Chart, just returned as a single lookup instead of a table to scroll.
When the "closest match" isn't exact
Number, letter, and fractional drill sizes don't line up with each other on a clean grid — a number or letter drill's decimal size rarely lands exactly on a 64th, and vice versa. If the closest match shown is more than a couple thousandths off from your input, that's expected: it means there isn't a size in that system that matches closely, not a calculation error.
Verify before cutting anything critical
These decimal equivalents follow standard ANSI B94.11M number, letter, and fractional drill sizes. Cross-check against your own drill index or a manufacturer's chart before committing to a tolerance-critical hole.