Drill bit size chart, every size, printable.

A drill bit size chart lists every standard drill with its diameter in decimal inches and millimetres. This one covers the four systems you meet: fractional drills from 1/64 to 63/64 inch, number drills from #80 to #1, letter drills from A to Z, and metric drills. Filter by system, type any size in inches or millimetres to find the nearest drill in each, and print the chart or save it as a CSV file.

How to use the drill bit size chart

1. Scroll the table, or press Fractional, Number, Letter or Metric under Show to see one system. All lists every size from smallest to largest.
2. To find a drill for a size, type it in Find nearest drill and choose Inches or Millimetres. A fraction such as 7/64 works.
3. Four cards show the nearest drill in each system and whether it is larger or smaller, and by how much. The best match is highlighted in the table too.
4. Press Print or save as PDF to print the table you are looking at, or Download CSV to open it in a spreadsheet.

The four systems

Fractional drills go up in steps of 1/64 inch, so every size is a number of 64ths: 1/64 is 0.0156 inch, 1/8 is 0.125 inch (3.175 mm), 1/4 is 0.25 inch (6.35 mm) and 1/2 is 0.5 inch (12.7 mm). The decimals here are exact.

Number drills run from #80, the smallest, at 0.0135 inch (0.343 mm) up to #1 at 0.228 inch (5.791 mm). The larger the number, the smaller the drill. #30 is 0.1285 inch, which is 3.264 mm.

Letter drills run from A at 0.234 inch (5.944 mm) to Z at 0.413 inch (10.490 mm). Here the later the letter, the bigger the drill. F is 0.257 inch, or 6.528 mm. The letter E is the same as 1/4 inch, 0.250.

Metric drills are named by their diameter in millimetres, so no table is needed to know a size. This chart lists 0.5 mm steps from 0.5 mm to 13 mm as a convenient set. Which metric sizes are stocked varies, and no official list was read for this page.

Finding the nearest drill, with examples

6 mm. That is 0.2362 inch. The metric 6.0 mm drill matches it exactly. Among the inch drills, 15/64 (0.2344 inch) is 0.0018 inch smaller and letter B (0.238 inch) is 0.0018 inch larger.

0.2 inch. The nearest number drill is #7 at 0.201 inch, only 0.001 inch larger. #8 at 0.199 is just as close on the other side, and when two are equally close this chart shows the larger one. The nearest fractional drill is 13/64 at 0.2031 inch.

3.5 mm. That is 0.1378 inch. The metric 3.5 mm drill is exact. The nearest number drill is #29 at 0.136 inch, 0.0018 inch smaller, and the nearest fraction is 9/64 at 0.1406 inch, 0.0028 inch larger.

Where the numbers come from

The decimal inch sizes of the number and letter drills are copied from the table in AND10387 Rev 6, an Air Force-Navy Aeronautical Design Standard for drill sizes and drilled hole tolerances (reactivated 16 Sep 1974). It is a scan, and the EverySpec site that hosts it lists its status as cancelled. The ASME standard for twist drills, B94.11M (1993 edition), is sold for a fee and was not read, so this page does not claim it says the same. The fractional sizes are exact 64ths, and millimetres are the inch value times 25.4, the exact definition of the inch.

Tap drill sizes, which depend on a thread table, are not given here because no official thread table was read for this page. Check the thread standard or the tap's packaging.

Common problems

• The size you need falls between two drills. Choose by what the hole is for. The cards show the gap in thousandths of an inch and in millimetres.
• A number drill looks backwards. #10 (0.1935 inch) is smaller than #9 (0.196 inch). The larger the number, the smaller the hole.
• Your chart from a shop shows a slightly different decimal. Charts round differently and some give three places where others give four.

To change a fraction of an inch into millimetres, try , and for other lengths the inches to cm converter.