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Tap drill lookup.

Recommended tap drill diameters for UNC, UNF, metric coarse, and metric fine threads. ~75% thread engagement per Machinery's Handbook. Search or filter.

Size Series Major Ø Pitch / TPI Tap drill Drill
#1-64 UNC 0.0730″ 1.85 mm 64 TPI 0.0595″ 1.51 mm #53
#2-56 UNC 0.0860″ 2.18 mm 56 TPI 0.0700″ 1.78 mm #50
#3-48 UNC 0.0990″ 2.51 mm 48 TPI 0.0785″ 1.99 mm #47
#4-40 UNC 0.1120″ 2.84 mm 40 TPI 0.0890″ 2.26 mm #43
#5-40 UNC 0.1250″ 3.17 mm 40 TPI 0.1015″ 2.58 mm #38
#6-32 UNC 0.1380″ 3.51 mm 32 TPI 0.1065″ 2.71 mm #36
#8-32 UNC 0.1640″ 4.17 mm 32 TPI 0.1360″ 3.45 mm #29
#10-24 UNC 0.1900″ 4.83 mm 24 TPI 0.1495″ 3.80 mm #25
#12-24 UNC 0.2160″ 5.49 mm 24 TPI 0.1770″ 4.50 mm #16
1/4-20 UNC 0.2500″ 6.35 mm 20 TPI 0.2010″ 5.11 mm #7
5/16-18 UNC 0.3125″ 7.94 mm 18 TPI 0.2570″ 6.53 mm F
3/8-16 UNC 0.3750″ 9.52 mm 16 TPI 0.3125″ 7.94 mm 5/16
7/16-14 UNC 0.4375″ 11.11 mm 14 TPI 0.3680″ 9.35 mm U
1/2-13 UNC 0.5000″ 12.70 mm 13 TPI 0.4219″ 10.72 mm 27/64
9/16-12 UNC 0.5625″ 14.29 mm 12 TPI 0.4844″ 12.30 mm 31/64
5/8-11 UNC 0.6250″ 15.88 mm 11 TPI 0.5313″ 13.50 mm 17/32
3/4-10 UNC 0.7500″ 19.05 mm 10 TPI 0.6562″ 16.67 mm 21/32
7/8-9 UNC 0.8750″ 22.22 mm 9 TPI 0.7656″ 19.45 mm 49/64
1-8 UNC 1.0000″ 25.40 mm 8 TPI 0.8750″ 22.22 mm 7/8
1 1/8-7 UNC 1.1250″ 28.57 mm 7 TPI 0.9844″ 25.00 mm 63/64
1 1/4-7 UNC 1.2500″ 31.75 mm 7 TPI 1.1094″ 28.18 mm 1 7/64
1 1/2-6 UNC 1.5000″ 38.10 mm 6 TPI 1.3281″ 33.73 mm 1 21/64
#0-80 UNF 0.0600″ 1.52 mm 80 TPI 0.0469″ 1.19 mm 3/64
#1-72 UNF 0.0730″ 1.85 mm 72 TPI 0.0595″ 1.51 mm #53
#2-64 UNF 0.0860″ 2.18 mm 64 TPI 0.0700″ 1.78 mm #50
#3-56 UNF 0.0990″ 2.51 mm 56 TPI 0.0820″ 2.08 mm #45
#4-48 UNF 0.1120″ 2.84 mm 48 TPI 0.0935″ 2.37 mm #42
#5-44 UNF 0.1250″ 3.17 mm 44 TPI 0.1040″ 2.64 mm #37
#6-40 UNF 0.1380″ 3.51 mm 40 TPI 0.1130″ 2.87 mm #33
#8-36 UNF 0.1640″ 4.17 mm 36 TPI 0.1360″ 3.45 mm #29
#10-32 UNF 0.1900″ 4.83 mm 32 TPI 0.1590″ 4.04 mm #21
#12-28 UNF 0.2160″ 5.49 mm 28 TPI 0.1820″ 4.62 mm #14
1/4-28 UNF 0.2500″ 6.35 mm 28 TPI 0.2130″ 5.41 mm #3
5/16-24 UNF 0.3125″ 7.94 mm 24 TPI 0.2720″ 6.91 mm I
3/8-24 UNF 0.3750″ 9.52 mm 24 TPI 0.3320″ 8.43 mm Q
7/16-20 UNF 0.4375″ 11.11 mm 20 TPI 0.3906″ 9.92 mm 25/64
1/2-20 UNF 0.5000″ 12.70 mm 20 TPI 0.4531″ 11.51 mm 29/64
9/16-18 UNF 0.5625″ 14.29 mm 18 TPI 0.5156″ 13.10 mm 33/64
5/8-18 UNF 0.6250″ 15.88 mm 18 TPI 0.5781″ 14.68 mm 37/64
3/4-16 UNF 0.7500″ 19.05 mm 16 TPI 0.6875″ 17.46 mm 11/16
7/8-14 UNF 0.8750″ 22.22 mm 14 TPI 0.8125″ 20.64 mm 13/16
1-12 UNF 1.0000″ 25.40 mm 12 TPI 0.9219″ 23.42 mm 59/64
1 1/4-12 UNF 1.2500″ 31.75 mm 12 TPI 1.1719″ 29.77 mm 1 11/64
1 1/2-12 UNF 1.5000″ 38.10 mm 12 TPI 1.4219″ 36.12 mm 1 27/64
M2 MC 0.0787″ 2.00 mm 0.4 mm 0.0630″ 1.60 mm 1.6 mm
M2.5 MC 0.0984″ 2.50 mm 0.45 mm 0.0807″ 2.05 mm 2.05 mm
M3 MC 0.1181″ 3.00 mm 0.5 mm 0.0984″ 2.50 mm 2.5 mm
M4 MC 0.1575″ 4.00 mm 0.7 mm 0.1299″ 3.30 mm 3.3 mm
M5 MC 0.1969″ 5.00 mm 0.8 mm 0.1654″ 4.20 mm 4.2 mm
M6 MC 0.2362″ 6.00 mm 1 mm 0.1969″ 5.00 mm 5.0 mm
M8 MC 0.3150″ 8.00 mm 1.25 mm 0.2677″ 6.80 mm 6.8 mm
M10 MC 0.3937″ 10.00 mm 1.5 mm 0.3346″ 8.50 mm 8.5 mm
M12 MC 0.4724″ 12.00 mm 1.75 mm 0.4016″ 10.20 mm 10.2 mm
M14 MC 0.5512″ 14.00 mm 2 mm 0.4724″ 12.00 mm 12.0 mm
M16 MC 0.6299″ 16.00 mm 2 mm 0.5512″ 14.00 mm 14.0 mm
M20 MC 0.7874″ 20.00 mm 2.5 mm 0.6890″ 17.50 mm 17.5 mm
M24 MC 0.9449″ 24.00 mm 3 mm 0.8268″ 21.00 mm 21.0 mm
M30 MC 1.1811″ 30.00 mm 3.5 mm 1.0433″ 26.50 mm 26.5 mm
M3 × 0.35 MF 0.1181″ 3.00 mm 0.35 mm 0.1043″ 2.65 mm 2.65 mm
M4 × 0.5 MF 0.1575″ 4.00 mm 0.5 mm 0.1378″ 3.50 mm 3.5 mm
M5 × 0.5 MF 0.1969″ 5.00 mm 0.5 mm 0.1772″ 4.50 mm 4.5 mm
M6 × 0.75 MF 0.2362″ 6.00 mm 0.75 mm 0.2067″ 5.25 mm 5.25 mm
M8 × 1.0 MF 0.3150″ 8.00 mm 1 mm 0.2756″ 7.00 mm 7.0 mm
M10 × 1.25 MF 0.3937″ 10.00 mm 1.25 mm 0.3465″ 8.80 mm 8.8 mm
M12 × 1.25 MF 0.4724″ 12.00 mm 1.25 mm 0.4232″ 10.75 mm 10.75 mm
M12 × 1.5 MF 0.4724″ 12.00 mm 1.5 mm 0.4134″ 10.50 mm 10.5 mm
M14 × 1.5 MF 0.5512″ 14.00 mm 1.5 mm 0.4921″ 12.50 mm 12.5 mm
M16 × 1.5 MF 0.6299″ 16.00 mm 1.5 mm 0.5709″ 14.50 mm 14.5 mm
M20 × 1.5 MF 0.7874″ 20.00 mm 1.5 mm 0.7283″ 18.50 mm 18.5 mm
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75% thread engagement

These drill diameters target ~75% thread engagement — the standard rule for general-purpose threading. Beyond ~75% the strength gain is marginal but tapping torque rises sharply, increasing tap-breakage risk in tough materials.

For form (roll) taps

Form taps need a larger pre-tap hole than cut taps — the metal flows into the threads. Add roughly 0.0025″ (0.06 mm) to the values shown for form-tapped holes in ductile materials. Check your tap manufacturer's chart for exact recommendations.

Keep exploring

Related tools & references

Thread specs reference→

Pitch, major/minor diameters, and classes for UN and metric.

Drill size chart→

Decimal equivalents for number, letter, and fractional drills.

Clearance hole chart→

Through-hole sizes for the matching fastener.

Thread engagement calculator→

Minimum tapped depth so threads don't strip.

Bolt torque calculator→

Tightening torque for the fastener you're tapping for.

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