Metric shop approximation
Tap drill ≈ nominal diameter − pitchThis is a convenient cut-thread starting rule, not a finished-hole tolerance or form-tap formula.
Machining reference / interactive lookup
Tap Drill Chart: Metric, UNC & UNF Sizes
Search 83 common 60-degree cut-tap starting sizes, filter by thread family, or enter an available drill diameter to find the closest chart matches.
Matches designations, series, pitches, drill names, and decimal sizes.
Shows the five closest chart values; it does not approve the process.
Showing all 83 chart sizes.
Closest chart matches
Closest does not mean acceptable. Confirm the hole range and engagement with the tap manufacturer.
No chart rows match the current search and family filter. Clear the filters or use the custom engagement calculator.
Metric tap drill chart
Common ISO metric coarse and fine 60-degree cut-thread starting sizes. Nominal diameter minus pitch is a shop approximation near typical engagement levels.
| Thread | Series | Pitch (mm) | Tap drill (mm) | Decimal inch | Copy row |
|---|---|---|---|---|---|
| M1 × 0.25 | Coarse | 0.25 | 0.75 | 0.0295 | |
| M1.2 × 0.25 | Coarse | 0.25 | 0.95 | 0.0374 | |
| M1.4 × 0.30 | Coarse | 0.30 | 1.10 | 0.0433 | |
| M1.6 × 0.35 | Coarse | 0.35 | 1.25 | 0.0492 | |
| M1.8 × 0.35 | Coarse | 0.35 | 1.45 | 0.0571 | |
| M2 × 0.40 | Coarse | 0.40 | 1.60 | 0.0630 | |
| M2.2 × 0.45 | Coarse | 0.45 | 1.75 | 0.0689 | |
| M2.5 × 0.45 | Coarse | 0.45 | 2.05 | 0.0807 | |
| M3 × 0.50 | Coarse | 0.50 | 2.50 | 0.0984 | |
| M3.5 × 0.60 | Coarse | 0.60 | 2.90 | 0.1142 | |
| M4 × 0.70 | Coarse | 0.70 | 3.30 | 0.1299 | |
| M4.5 × 0.75 | Coarse | 0.75 | 3.70 | 0.1457 | |
| M5 × 0.80 | Coarse | 0.80 | 4.20 | 0.1654 | |
| M6 × 1.00 | Coarse | 1.00 | 5.00 | 0.1969 | |
| M7 × 1.00 | Coarse | 1.00 | 6.00 | 0.2362 | |
| M8 × 1.25 | Coarse | 1.25 | 6.80 | 0.2677 | |
| M8 × 1.00 | Fine | 1.00 | 7.00 | 0.2756 | |
| M10 × 1.50 | Coarse | 1.50 | 8.50 | 0.3346 | |
| M10 × 1.25 | Fine | 1.25 | 8.80 | 0.3465 | |
| M10 × 1.00 | Fine | 1.00 | 9.00 | 0.3543 | |
| M12 × 1.75 | Coarse | 1.75 | 10.20 | 0.4016 | |
| M12 × 1.50 | Fine | 1.50 | 10.50 | 0.4134 | |
| M12 × 1.25 | Fine | 1.25 | 10.80 | 0.4252 | |
| M14 × 2.00 | Coarse | 2.00 | 12.00 | 0.4724 | |
| M14 × 1.50 | Fine | 1.50 | 12.50 | 0.4921 | |
| M16 × 2.00 | Coarse | 2.00 | 14.00 | 0.5512 | |
| M16 × 1.50 | Fine | 1.50 | 14.50 | 0.5709 | |
| M18 × 2.50 | Coarse | 2.50 | 15.50 | 0.6102 | |
| M18 × 1.50 | Fine | 1.50 | 16.50 | 0.6496 | |
| M20 × 2.50 | Coarse | 2.50 | 17.50 | 0.6890 | |
| M20 × 1.50 | Fine | 1.50 | 18.50 | 0.7283 | |
| M22 × 2.50 | Coarse | 2.50 | 19.50 | 0.7677 | |
| M22 × 1.50 | Fine | 1.50 | 20.50 | 0.8071 | |
| M24 × 3.00 | Coarse | 3.00 | 21.00 | 0.8268 | |
| M24 × 2.00 | Fine | 2.00 | 22.00 | 0.8661 | |
| M27 × 3.00 | Coarse | 3.00 | 24.00 | 0.9449 | |
| M27 × 2.00 | Fine | 2.00 | 25.00 | 0.9843 | |
| M30 × 3.50 | Coarse | 3.50 | 26.50 | 1.0433 | |
| M30 × 2.00 | Fine | 2.00 | 28.00 | 1.1024 | |
| M33 × 3.50 | Coarse | 3.50 | 29.50 | 1.1614 | |
| M33 × 2.00 | Fine | 2.00 | 31.00 | 1.2205 | |
| M36 × 4.00 | Coarse | 4.00 | 32.00 | 1.2598 | |
| M36 × 3.00 | Fine | 3.00 | 33.00 | 1.2992 | |
| M36 × 2.00 | Fine | 2.00 | 34.00 | 1.3386 |
UNC and UNF tap drill chart
Number, letter, fractional, and decimal drill designations are shown together for common Unified 60-degree cut threads.
| Thread | Series | TPI | Tap drill | Decimal inch | Metric equivalent | Copy row |
|---|---|---|---|---|---|---|
| #0-80 | UNF | 80 | 3/64 | 0.0469 | 1.19 mm | |
| #1-64 | UNC | 64 | #53 | 0.0595 | 1.51 mm | |
| #1-72 | UNF | 72 | #53 | 0.0595 | 1.51 mm | |
| #2-56 | UNC | 56 | #50 | 0.0700 | 1.78 mm | |
| #2-64 | UNF | 64 | #50 | 0.0700 | 1.78 mm | |
| #3-48 | UNC | 48 | #47 | 0.0785 | 1.99 mm | |
| #3-56 | UNF | 56 | #45 | 0.0820 | 2.08 mm | |
| #4-40 | UNC | 40 | #43 | 0.0890 | 2.26 mm | |
| #4-48 | UNF | 48 | #42 | 0.0935 | 2.37 mm | |
| #5-40 | UNC | 40 | #38 | 0.1015 | 2.58 mm | |
| #5-44 | UNF | 44 | #37 | 0.1040 | 2.64 mm | |
| #6-32 | UNC | 32 | #36 | 0.1065 | 2.71 mm | |
| #6-40 | UNF | 40 | #33 | 0.1130 | 2.87 mm | |
| #8-32 | UNC | 32 | #29 | 0.1360 | 3.45 mm | |
| #8-36 | UNF | 36 | #29 | 0.1360 | 3.45 mm | |
| #10-24 | UNC | 24 | #25 | 0.1495 | 3.80 mm | |
| #10-32 | UNF | 32 | #21 | 0.1590 | 4.04 mm | |
| #12-24 | UNC | 24 | #16 | 0.1770 | 4.50 mm | |
| #12-28 | UNF | 28 | #14 | 0.1820 | 4.62 mm | |
| 1/4-20 | UNC | 20 | #7 | 0.2010 | 5.11 mm | |
| 1/4-28 | UNF | 28 | #3 | 0.2130 | 5.41 mm | |
| 5/16-18 | UNC | 18 | F | 0.2570 | 6.53 mm | |
| 5/16-24 | UNF | 24 | I | 0.2720 | 6.91 mm | |
| 3/8-16 | UNC | 16 | 5/16 | 0.3125 | 7.94 mm | |
| 3/8-24 | UNF | 24 | Q | 0.3320 | 8.43 mm | |
| 7/16-14 | UNC | 14 | U | 0.3680 | 9.35 mm | |
| 7/16-20 | UNF | 20 | 25/64 | 0.3906 | 9.92 mm | |
| 1/2-13 | UNC | 13 | 27/64 | 0.4219 | 10.72 mm | |
| 1/2-20 | UNF | 20 | 29/64 | 0.4531 | 11.51 mm | |
| 9/16-12 | UNC | 12 | 31/64 | 0.4844 | 12.30 mm | |
| 9/16-18 | UNF | 18 | 33/64 | 0.5156 | 13.10 mm | |
| 5/8-11 | UNC | 11 | 17/32 | 0.5313 | 13.50 mm | |
| 5/8-18 | UNF | 18 | 37/64 | 0.5781 | 14.68 mm | |
| 3/4-10 | UNC | 10 | 21/32 | 0.6563 | 16.67 mm | |
| 3/4-16 | UNF | 16 | 11/16 | 0.6875 | 17.46 mm | |
| 7/8-9 | UNC | 9 | 49/64 | 0.7656 | 19.45 mm | |
| 7/8-14 | UNF | 14 | 13/16 | 0.8125 | 20.64 mm | |
| 1-8 | UNC | 8 | 7/8 | 0.8750 | 22.23 mm | |
| 1-12 | UNF | 12 | 59/64 | 0.9219 | 23.42 mm |
How to use the chart
Choose a starting size, then verify the process
Custom engagement estimate
Drill = D − (0.01299 × engagement % × pitch)Use the Tap Drill Size Calculator when the required engagement or thread geometry differs.
Production application disclaimerThese values are common starting sizes for 60-degree cut taps. Confirm the tap maker’s permitted hole range, thread class, material, coating, hole depth, tolerance, and required engagement. Form and roll taps require manufacturer-specific pre-drill sizes.
Standards context: ISO 261 and ISO 724 cover general-purpose metric thread series and basic dimensions; ASME B1.1 covers Unified inch screw threads. This page is a practical lookup, not a reproduction of those standards.
Last reviewed: September 4, 2026 · Review method: designation, decimal conversion, filter, copy, and nearest-match checks.
Practical questions
Tap drill chart FAQ
What tap drill size should I use?
Start with the row for the exact thread designation. Then confirm the permitted hole range against the tap manufacturer, required engagement, material, thread class, and blind- or through-hole conditions.
Why does thread engagement change tap drill size?
A smaller drilled hole leaves more material for the tap and generally raises theoretical engagement. It also raises tapping torque and can increase the risk of tap failure.
Can this cut-tap chart be used for form taps?
No. Form and roll taps displace material rather than cutting it and normally need a larger, manufacturer-specified pre-drill diameter.
Should I use the calculated diameter or the nearest stocked drill?
Treat the calculated diameter as a geometric estimate. Select a stocked drill only after checking the permitted finished-hole range, expected runout, coating, and manufacturer data.