Drill bit size converter
Enter a size in any system — millimetres, a decimal inch, a fraction, or a number or letter bit — and get the nearest actual drill bit, with its equivalents across every system.
Entering a size in
Enter millimetres — e.g. 6, 6.5, 10.
Nearest drill bit
You entered 6 mm = 0.2362" · 6 mm
No bit matches exactly — the two closest are:
Nearest larger
B
0.238"6.05 mmLetter
≈ 15/64" fraction
+0.05 mm vs. enteredNearest smaller
15/64"
0.2344"5.95 mmFraction
−0.05 mm vs. enteredFor a hole a screw or part must pass through, the nearest larger bit is usually the safer pick. Going into wood for grip, smaller holds tighter. Your call.
How to read it
Pick the system you have a size in, type the value, and the converter finds the nearest real drill bit. Every bit is shown with its decimal inch and millimetre equivalents, and number/letter bits also name the closest fraction — so you can move between systems at a glance.
When nothing matches exactly (most metric and decimal values), it shows the nearest bit just above and just below, so you can pick a slightly bigger or smaller hole.
The four drill-bit systems
- Fractional — sized in 64ths of an inch, 1/64" up to 1" and beyond (the common home set).
- Number / wire gauge — #1 (0.228") down to #80 (0.0135"), for small precise holes.
- Letter — A (0.234") up to Z (0.413"), filling the gaps between fractions in the mid range.
- Metric — straight millimetres; shown here as the mm equivalent of every bit.
Common questions
What drill bit is closest to 6mm?
No inch-system bit is exactly 6 mm, but the closest are 15/64" (0.234", 5.95 mm — just under) and, if you have letter bits, letter B (0.238", 6.05 mm — just over); the nearest fraction over 6 mm is 1/4" (0.25", 6.35 mm). If you own metric bits, a 6 mm bit is of course exact. For a hole something must pass through, pick the slightly larger size.
How do I convert mm to a drill bit size?
Divide the millimetre value by 25.4 to get the size in decimal inches, then match that to the nearest fractional, number (#1–#80) or letter (A–Z) drill bit. The converter does it for you — enter the millimetres and it returns the nearest bit at or above and below, with the decimal-inch and fraction equivalents.
What is 0.472 inches as a drill bit?
0.472" is almost exactly 12 mm. The nearest standard inch bits are 15/32" (0.469", 11.91 mm — just under) and 31/64" (0.484", 12.3 mm — just over). So for a 0.472" hole, a 15/32" bit is the closest single size, or a 12 mm metric bit if you have one.
Get the gear
As an Amazon Associate, WhatDrillBit earns from qualifying purchases.
Drill bit decimal and millimetre equivalents are fixed industry-standard values. Bit diameters are nominal; a real bit and hole can vary slightly with the bit and material — for precision work, measure the bit.