Tap drill chart: UNC and UNF
Every Unified inch thread from #0-80 to 1 inch. Read across: the thread, the drill to tap it, the drill's size in inches and millimeters, how much of a full thread it leaves, and the drill for a screw that passes through. The drill is the number, letter or fractional size closest to 75% thread, the figure tap makers design for. Tap a thread for alternatives and a scale drawing.
| Thread | Tap drill | Inch | mm | % | Clear. |
|---|---|---|---|---|---|
| #1-64 | #53 | 0.05951.51 mm | 1.51 | 67% | – |
| #2-56 | #50 | 0.07001.78 mm | 1.78 | 69% | – |
| #3-48 | #47 | 0.07851.99 mm | 1.99 | 76% | – |
| #4-40 | #43 | 0.08902.26 mm | 2.26 | 71% | – |
| #5-40 | #38 | 0.10152.58 mm | 2.58 | 72% | – |
| #6-32 | #36 | 0.10652.71 mm | 2.71 | 78% | #18 0.170 |
| #8-32 | #29 | 0.13603.45 mm | 3.45 | 69% | #9 0.196 |
| #10-24 | #25 | 0.14953.80 mm | 3.80 | 75% | #2 0.221 |
| #12-24 | #16 | 0.17704.50 mm | 4.50 | 72% | – |
| 1/4-20 | #7 | 0.20105.11 mm | 5.11 | 75% | 9/32" 0.281 |
| 5/16-18 | F | 0.25706.53 mm | 6.53 | 77% | 11/32" 0.344 |
| 3/8-16 | 5/16" | 0.31257.94 mm | 7.94 | 77% | 13/32" 0.406 |
| 7/16-14 | U | 0.36809.35 mm | 9.35 | 75% | – |
| 1/2-13 | 27/64" | 0.421910.72 mm | 10.72 | 78% | 9/16" 0.562 |
| 9/16-12 | 31/64" | 0.484412.30 mm | 12.30 | 72% | – |
| 5/8-11 | 17/32" | 0.531313.49 mm | 13.49 | 79% | 11/16" 0.688 |
| 3/4-10 | 21/32" | 0.656316.67 mm | 16.67 | 72% | 13/16" 0.812 |
| 7/8-9 | 49/64" | 0.765619.45 mm | 19.45 | 76% | – |
| 1-8 | 7/8" | 0.875022.23 mm | 22.23 | 77% | – |
| Thread | Tap drill | Inch | mm | % | Clear. |
|---|---|---|---|---|---|
| #0-80 | 3/64" | 0.04691.19 mm | 1.19 | 81% | – |
| #1-72 | #53 | 0.05951.51 mm | 1.51 | 75% | – |
| #2-64 | #50 | 0.07001.78 mm | 1.78 | 79% | – |
| #3-56 | #45 | 0.08202.08 mm | 2.08 | 73% | – |
| #4-48 | #42 | 0.09352.38 mm | 2.38 | 68% | – |
| #5-44 | #37 | 0.10402.64 mm | 2.64 | 71% | – |
| #6-40 | #33 | 0.11302.87 mm | 2.87 | 77% | #18 0.170 |
| #8-36 | #29 | 0.13603.45 mm | 3.45 | 78% | #9 0.196 |
| #10-32 | #21 | 0.15904.04 mm | 4.04 | 76% | #2 0.221 |
| #12-28 | #14 | 0.18204.62 mm | 4.62 | 73% | – |
| 1/4-28 | #3 | 0.21305.41 mm | 5.41 | 80% | 9/32" 0.281 |
| 5/16-24 | I | 0.27206.91 mm | 6.91 | 75% | 11/32" 0.344 |
| 3/8-24 | Q | 0.33208.43 mm | 8.43 | 79% | 13/32" 0.406 |
| 7/16-20 | 25/64" | 0.39069.92 mm | 9.92 | 72% | – |
| 1/2-20 | 29/64" | 0.453111.51 mm | 11.51 | 72% | 9/16" 0.562 |
| 9/16-18 | 33/64" | 0.515613.10 mm | 13.10 | 65% | – |
| 5/8-18 | 37/64" | 0.578114.69 mm | 14.69 | 65% | 11/16" 0.688 |
| 3/4-16 | 11/16" | 0.687517.46 mm | 17.46 | 77% | 13/16" 0.812 |
| 7/8-14 | 13/16" | 0.812520.64 mm | 20.64 | 67% | – |
| 1-12 | 59/64" | 0.921923.42 mm | 23.42 | 72% | – |
Clearance is the ASME B18.2.8 normal fit, shown only where two independent reproductions of the standard agree. Thread percentage uses the basic thread height (formula on How we calculate).