Tap Drill Chart: Inch and Metric
All 45 threads in one printable chart: numbered screws, inch UNC and UNF, and metric coarse. Each row shows the drill for aluminum, steel and stainless.
| Thread | Series | Major diameter | Pitch | Aluminum, brass (75%) | Mild steel (60%) | Stainless, titanium (50%) |
|---|---|---|---|---|---|---|
| #0-80 | UNF | 0.0600 in (1.52 mm) | 80 TPI (0.318 mm) | 3/64 in 81% | 3/64 in 81% | #55 49% |
| #2-56 | UNC | 0.0860 in (2.18 mm) | 56 TPI (0.454 mm) | #50 69% | #49 56% | #49 56% |
| #4-40 | UNC | 0.1120 in (2.84 mm) | 40 TPI (0.635 mm) | #43 71% | #42 57% | #41 49% |
| #5-40 | UNC | 0.1250 in (3.17 mm) | 40 TPI (0.635 mm) | #38 72% | #37 65% | 7/64 in 48% |
| #6-32 | UNC | 0.1380 in (3.51 mm) | 32 TPI (0.794 mm) | #36 78% | #33 62% | #32 54% |
| #6-40 | UNF | 0.1380 in (3.51 mm) | 40 TPI (0.635 mm) | #33 77% | #31 55% | #31 55% |
| #8-32 | UNC | 0.1640 in (4.17 mm) | 32 TPI (0.794 mm) | #29 69% | #28 58% | #27 49% |
| #10-24 | UNC | 0.1900 in (4.83 mm) | 24 TPI (1.058 mm) | #25 75% | #22 61% | #20 54% |
| #10-32 | UNF | 0.1900 in (4.83 mm) | 32 TPI (0.794 mm) | #21 76% | #19 59% | #18 50% |
| #12-24 | UNC | 0.2160 in (5.49 mm) | 24 TPI (1.058 mm) | #16 72% | #14 63% | #12 50% |
| 1/4-20 | UNC | 0.2500 in (6.35 mm) | 20 TPI (1.270 mm) | #7 75% | #4 63% | 7/32 in 48% |
| 5/16-18 | UNC | 0.3125 in (7.94 mm) | 18 TPI (1.411 mm) | letter F 77% | letter H 64% | letter J 49% |
| 3/8-16 | UNC | 0.3750 in (9.52 mm) | 16 TPI (1.587 mm) | 5/16 in 77% | letter P 64% | letter Q 53% |
| 7/16-14 | UNC | 0.4375 in (11.11 mm) | 14 TPI (1.814 mm) | letter U 75% | letter V 65% | 25/64 in 51% |
| 1/2-13 | UNC | 0.5000 in (12.70 mm) | 13 TPI (1.954 mm) | 27/64 in 78% | 7/16 in 63% | 29/64 in 47% |
| 9/16-12 | UNC | 0.5625 in (14.29 mm) | 12 TPI (2.117 mm) | 31/64 in 72% | 1/2 in 58% | 1/2 in 58% |
| 5/8-11 | UNC | 0.6250 in (15.88 mm) | 11 TPI (2.309 mm) | 17/32 in 79% | 35/64 in 66% | 9/16 in 53% |
| 3/4-10 | UNC | 0.7500 in (19.05 mm) | 10 TPI (2.540 mm) | 21/32 in 72% | 43/64 in 60% | 11/16 in 48% |
| 7/8-9 | UNC | 0.8750 in (22.22 mm) | 9 TPI (2.822 mm) | 49/64 in 76% | 25/32 in 65% | 51/64 in 54% |
| 1/4-28 | UNF | 0.2500 in (6.35 mm) | 28 TPI (0.907 mm) | #3 80% | #2 63% | #1 47% |
| 5/16-24 | UNF | 0.3125 in (7.94 mm) | 24 TPI (1.058 mm) | letter I 75% | letter K 58% | 9/32 in 58% |
| 3/8-24 | UNF | 0.3750 in (9.52 mm) | 24 TPI (1.058 mm) | letter Q 79% | letter R 67% | letter S 50% |
| 7/16-20 | UNF | 0.4375 in (11.11 mm) | 20 TPI (1.270 mm) | 25/64 in 72% | letter X 62% | 13/32 in 48% |
| 1/2-20 | UNF | 0.5000 in (12.70 mm) | 20 TPI (1.270 mm) | 29/64 in 72% | 29/64 in 72% | 15/32 in 48% |
| 9/16-18 | UNF | 0.5625 in (14.29 mm) | 18 TPI (1.411 mm) | 33/64 in 65% | 33/64 in 65% | 33/64 in 65% |
| 5/8-18 | UNF | 0.6250 in (15.88 mm) | 18 TPI (1.411 mm) | 37/64 in 65% | 37/64 in 65% | 37/64 in 65% |
| 3/4-16 | UNF | 0.7500 in (19.05 mm) | 16 TPI (1.587 mm) | 11/16 in 77% | 45/64 in 58% | 45/64 in 58% |
| 7/8-14 | UNF | 0.8750 in (22.22 mm) | 14 TPI (1.814 mm) | 13/16 in 67% | 13/16 in 67% | 53/64 in 51% |
| M2 | Metric coarse | 2.000 mm (0.0787 in) | 0.40 mm | 1.6 mm 77% | 1.7 mm 58% | 1.7 mm 58% |
| M2.5 | Metric coarse | 2.500 mm (0.0984 in) | 0.45 mm | 2.05 mm 77% | 2.1 mm 68% | 2.2 mm 51% |
| M3 | Metric coarse | 3.000 mm (0.1181 in) | 0.50 mm | 2.5 mm 77% | 2.6 mm 62% | 2.7 mm 46% |
| M3.5 | Metric coarse | 3.500 mm (0.1378 in) | 0.60 mm | 2.9 mm 77% | 3.0 mm 64% | 3.1 mm 51% |
| M4 | Metric coarse | 4.000 mm (0.1575 in) | 0.70 mm | 3.3 mm 77% | 3.4 mm 66% | 3.5 mm 55% |
| M5 | Metric coarse | 5.000 mm (0.1969 in) | 0.80 mm | 4.2 mm 77% | 4.4 mm 58% | 4.5 mm 48% |
| M6 | Metric coarse | 6.000 mm (0.2362 in) | 1.00 mm | 5.0 mm 77% | 5.2 mm 62% | 5.3 mm 54% |
| M8 | Metric coarse | 8.000 mm (0.3150 in) | 1.25 mm | 6.8 mm 74% | 7.0 mm 62% | 7.2 mm 49% |
| M10 | Metric coarse | 10.000 mm (0.3937 in) | 1.50 mm | 8.5 mm 77% | 8.8 mm 62% | 9.0 mm 51% |
| M12 | Metric coarse | 12.000 mm (0.4724 in) | 1.75 mm | 10.2 mm 79% | 10.6 mm 62% | 10.9 mm 48% |
| M14 | Metric coarse | 14.000 mm (0.5512 in) | 2.00 mm | 12.0 mm 77% | 12.4 mm 62% | 12.7 mm 50% |
| M16 | Metric coarse | 16.000 mm (0.6299 in) | 2.00 mm | 14.0 mm 77% | 14.4 mm 62% | 14.7 mm 50% |
| M18 | Metric coarse | 18.000 mm (0.7087 in) | 2.50 mm | 15.5 mm 77% | 16.1 mm 59% | 16.4 mm 49% |
| M20 | Metric coarse | 20.000 mm (0.7874 in) | 2.50 mm | 17.5 mm 77% | 18.1 mm 59% | 18.4 mm 49% |
| M22 | Metric coarse | 22.000 mm (0.8661 in) | 2.50 mm | 19.5 mm 77% | 20.1 mm 59% | 20.4 mm 49% |
| M24 | Metric coarse | 24.000 mm (0.9449 in) | 3.00 mm | 21.0 mm 77% | 21.7 mm 59% | 22.1 mm 49% |
| M30 | Metric coarse | 30.000 mm (1.1811 in) | 3.50 mm | 26.5 mm 77% | 27.3 mm 59% | 27.8 mm 48% |
Small percentages show the thread engagement each drill leaves. Click a thread for the full page.
Tap Drill Chart: Inch and Metric | tapdrillsize.com/tap-drill-chart/ | Last reviewed October 7, 2026 | Check your tap maker's chart before cutting.
How to read this chart
Each row is one thread. The three drill columns show the drill to use for that material. The small percentage under each drill is the share of a full thread it leaves.
The first drill column is the standard chart drill, the one most printed charts show. The steel and stainless columns use a bigger drill, so the tap cuts less and turns more easily.
Drill sizes come in steps, so a column can land a little above or below its target. The percentage shows by how much.
Which column should I use?
Use the first column for aluminum, brass and plastics, and for most through holes. Use the second for mild steel. Use the third for stainless steel, titanium and hardened steel, or for a blind hole in a hard metal.
FAQ
What is the tap drill size for 1/4-20?
#7 (0.2010 in, 5.11 mm) leaves about 75% thread. It is the drill most printed charts show for 1/4-20. The same row shows #4 for steel and 7/32 in for stainless.
Why do the steel and stainless drills differ from the standard drill?
A bigger drill leaves less thread, so the tap works less hard in tough metal. ToolGrit cites studies showing about 90% of a thread's shear strength at 60% thread, so the thread gives up little.
Where do these drill sizes come from?
The 75% drills match two published charts, from American Fastener and Fabworks. The percentages use the formula in the OSG chart, and the steel and stainless drills apply the targets from Texas Metalworks to the list of standard drills.
Does the chart include fine threads and pipe threads?
It includes UNF and numbered fine threads. Metric fine pitches such as M8 x 1 are on the metric chart. Pipe threads such as NPT are not covered yet.
Chart drills match the American Fastener tap and drill chart and the Fabworks tap drill chart. Thread percentages use the formula printed in the OSG tap drill chart, Vol 3 (2024). Last reviewed October 7, 2026. Method: how the numbers are calculated.