Tap & Drill Bit Size Chart
Tap & Drill Bit Size Chart
Mutual Screw & Supply · mutualscrew.com · (800) 222-0324
How to use this chart: Find your screw or bolt size to get the correct drill bit for tapping threads (tap drill) or for a clearance fit (clearance drill). Use the search box to jump directly to a size.
| Size | TPI | Tap Drill (Frac.) | Tap Drill (Dec./Letter) | % Thread | Clearance Drill (Frac.) | Clearance Drill (Dec./Letter) |
|---|---|---|---|---|---|---|
| Machine Screw Sizes | ||||||
| #0 | 80 | 3/64" | #56 (0.0465") | 75% | 1/16" | #51 (0.0670") |
| #1 | 64 | — | #53 (0.0595") | 75% | 5/64" | #47 (0.0785") |
| #2 | 56 | — | #50 (0.0700") | 75% | 3/32" | #42 (0.0935") |
| #3 | 48 | — | #47 (0.0785") | 75% | 7/64" | #37 (0.1040") |
| #4 | 40 | 3/32" | #43 (0.0890") | 75% | 1/8" | #31 (0.1200") |
| #5 | 40 | — | #38 (0.1015") | 75% | 9/64" | #29 (0.1360") |
| #6 | 32 | 7/64" | #36 (0.1065") | 75% | 9/64" | #25 (0.1495") |
| #8 | 32 | — | #29 (0.1360") | 75% | 11/64" | #16 (0.1770") |
| #10 | 24 | — | #25 (0.1495") | 75% | 3/16" | #9 (0.1960") |
| #12 | 24 | 11/64" | #16 (0.1770") | 75% | 7/32" | #2 (0.2210") |
| Fractional Sizes | ||||||
| 1/4" | 20 | 13/64" | #7 (0.2010") | 75% | 17/64" | F (0.2570") |
| 5/16" | 18 | 17/64" | #F (0.2570") | 75% | 21/64" | Q (0.3320") |
| 3/8" | 16 | 5/16" | 5/16 (0.3125") | 75% | 25/64" | W (0.3860") |
| 7/16" | 14 | U" | U (0.3680") | 75% | 29/64" | 29/64 (0.4531") |
| 1/2" | 13 | 27/64" | 27/64 (0.4219") | 75% | 33/64" | 33/64 (0.5156") |
| 9/16" | 12 | 31/64" | 31/64 (0.4844") | 75% | 37/64" | 37/64 (0.5781") |
| 5/8" | 11 | 17/32" | 17/32 (0.5313") | 75% | 41/64" | 41/64 (0.6406") |
| 3/4" | 10 | 21/32" | 21/32 (0.6563") | 75% | 49/64" | 49/64 (0.7656") |
| 7/8" | 9 | 49/64" | 49/64 (0.7656") | 75% | 57/64" | 57/64 (0.8906") |
| 1" | 8 | 7/8" | 7/8 (0.8750") | 75% | 1-1/64" | 1-1/64 (1.0156") |
| 1-1/8" | 7 | 63/64" | 63/64 (0.9844") | 75% | 1-9/64" | 1-9/64 (1.1406") |
| 1-1/4" | 7 | 1-7/64" | 1-7/64 (1.1094") | 75% | 1-17/64" | 1-17/64 (1.2656") |
| 1-1/2" | 6 | 1-11/32" | 1-11/32 (1.3438") | 75% | 1-33/64" | 1-33/64 (1.5156") |
| Size | TPI | Tap Drill (Frac.) | Tap Drill (Dec./Letter) | % Thread | Clearance Drill (Frac.) | Clearance Drill (Dec./Letter) |
|---|---|---|---|---|---|---|
| Machine Screw Sizes | ||||||
| #0 | 80 | 3/64" | #56 (0.0465") | 75% | 1/16" | #51 (0.0670") |
| #1 | 72 | — | #53 (0.0595") | 75% | 5/64" | #47 (0.0785") |
| #2 | 64 | — | #50 (0.0700") | 75% | 3/32" | #42 (0.0935") |
| #3 | 56 | — | #45 (0.0820") | 75% | 7/64" | #37 (0.1040") |
| #4 | 48 | 3/32" | #42 (0.0935") | 75% | 1/8" | #31 (0.1200") |
| #5 | 44 | — | #37 (0.1040") | 75% | 9/64" | #29 (0.1360") |
| #6 | 40 | — | #33 (0.1130") | 75% | 9/64" | #25 (0.1495") |
| #8 | 36 | — | #29 (0.1285") | 75% | 11/64" | #16 (0.1770") |
| #10 | 32 | 5/32" | #21 (0.1590") | 75% | 3/16" | #9 (0.1960") |
| #12 | 28 | — | #14 (0.1820") | 75% | 7/32" | #2 (0.2210") |
| Fractional Sizes | ||||||
| 1/4" | 28 | — | #3 (0.2130") | 75% | 17/64" | F (0.2570") |
| 5/16" | 24 | — | #I (0.2720") | 75% | 21/64" | Q (0.3320") |
| 3/8" | 24 | — | Q (0.3320") | 75% | 25/64" | W (0.3860") |
| 7/16" | 20 | 25/64" | 25/64 (0.3906") | 75% | 29/64" | 29/64 (0.4531") |
| 1/2" | 20 | 29/64" | 29/64 (0.4531") | 75% | 33/64" | 33/64 (0.5156") |
| 9/16" | 18 | 33/64" | 33/64 (0.5156") | 75% | 37/64" | 37/64 (0.5781") |
| 5/8" | 18 | 37/64" | 37/64 (0.5781") | 75% | 41/64" | 41/64 (0.6406") |
| 3/4" | 16 | 11/16" | 11/16 (0.6875") | 75% | 49/64" | 49/64 (0.7656") |
| 7/8" | 14 | 13/16" | 13/16 (0.8125") | 75% | 57/64" | 57/64 (0.8906") |
| 1" | 12 | 59/64" | 59/64 (0.9219") | 75% | 1-1/64" | 1-1/64 (1.0156") |
| Size | Pitch (mm) | Tap Drill (mm) | Tap Drill (in) | % Thread | Clearance Drill (mm) | Clearance Drill (in) |
|---|---|---|---|---|---|---|
| Coarse Thread (Standard) | ||||||
| M1.6 | 0.35 | 1.25 mm | — | 75% | 1.7 mm | — |
| M2 | 0.40 | 1.60 mm | #52 (0.0635") | 75% | 2.2 mm | #44 (0.0860") |
| M2.5 | 0.45 | 2.05 mm | #46 (0.0810") | 75% | 2.7 mm | #36 (0.1065") |
| M3 | 0.50 | 2.50 mm | #39 (0.0995") | 75% | 3.2 mm | #30 (0.1285") |
| M3.5 | 0.60 | 2.90 mm | #32 (0.1160") | 75% | 3.7 mm | #27 (0.1440") |
| M4 | 0.70 | 3.30 mm | #30 (0.1285") | 75% | 4.3 mm | #19 (0.1660") |
| M5 | 0.80 | 4.20 mm | #19 (0.1660") | 75% | 5.3 mm | — |
| M6 | 1.00 | 5.00 mm | #8 (0.1990") | 75% | 6.4 mm | — |
| M7 | 1.00 | 6.00 mm | — | 75% | 7.5 mm | — |
| M8 | 1.25 | 6.80 mm | H (0.2660") | 75% | 8.4 mm | — |
| M10 | 1.50 | 8.50 mm | R (0.3390") | 75% | 10.5 mm | — |
| M12 | 1.75 | 10.20 mm | — | 75% | 13.0 mm | — |
| M14 | 2.00 | 12.00 mm | — | 75% | 15.0 mm | — |
| M16 | 2.00 | 14.00 mm | — | 75% | 17.0 mm | — |
| M18 | 2.50 | 15.50 mm | — | 75% | 19.0 mm | — |
| M20 | 2.50 | 17.50 mm | — | 75% | 21.0 mm | — |
| M22 | 2.50 | 19.50 mm | — | 75% | 23.0 mm | — |
| M24 | 3.00 | 21.00 mm | — | 75% | 25.0 mm | — |
| M27 | 3.00 | 24.00 mm | — | 75% | 28.0 mm | — |
| M30 | 3.50 | 26.50 mm | — | 75% | 31.0 mm | — |
| M36 | 4.00 | 32.00 mm | — | 75% | 37.0 mm | — |
| Fine Thread (Selected Sizes) | ||||||
| M8 × 1.0 | 1.00 | 7.00 mm | — | 75% | 8.4 mm | — |
| M10 × 1.25 | 1.25 | 8.75 mm | — | 75% | 10.5 mm | — |
| M12 × 1.25 | 1.25 | 10.75 mm | — | 75% | 13.0 mm | — |
| M14 × 1.5 | 1.50 | 12.50 mm | — | 75% | 15.0 mm | — |
| M16 × 1.5 | 1.50 | 14.50 mm | — | 75% | 17.0 mm | — |
| M20 × 1.5 | 1.50 | 18.50 mm | — | 75% | 21.0 mm | — |
| M24 × 2.0 | 2.00 | 22.00 mm | — | 75% | 25.0 mm | — |
Tap Drill Size: Use this drill bit when you plan to cut (tap) internal threads into a hole. The tap drill removes just enough material so the tap can form threads with approximately 75% thread engagement — the industry standard balancing strength and tap life.
Clearance Drill Size: Use this drill bit when the fastener must pass through freely without threading — such as through the top piece in a bolted joint, or through a bracket. The clearance hole is slightly larger than the bolt diameter.
75% Thread Engagement: Threading to 100% sounds stronger but dramatically increases tap breakage risk. At 75% thread engagement you retain roughly 90% of the strength of a 100% thread — the standard used across manufacturing and construction.
UNC vs. UNF: UNC (Unified National Coarse) is the standard for most applications — faster to install, more resistant to cross-threading. UNF (Unified National Fine) provides greater strength and vibration resistance where needed. When in doubt, use UNC.
Letter & Number Drill Sizes: Drill bits are sized in three ways — fractional inches (1/4", 5/16"), numbers (#1–#80, where smaller numbers = larger bits), and letters (A–Z, where A is smallest). This chart shows all three so you can use whatever set you have on hand.
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Tap drill sizes based on 75% thread engagement per ASME B1.1 and B1.13M standards. Always verify for critical applications. — indicates no standard fractional/letter equivalent; use the nearest available size.