Tap Drill Size Charts

A tap drill chart determines what size hole to drill before tapping female threads and what size pipe is needed for male threads. Before starting to cut threads, there are a few factors to know to guarantee correct cutting:

1. Unified or metric: Screw sizes come in two classifications: unified and metric. Unified is used mainly in North America, while metric is used worldwide.
2. Major diameter: The major diameter is the largest diameter of an internal or external thread.
3. Pitch: The pitch is the distance between two adjacent threads on an internal or external thread.

Table of contents

• Tap drill size chart
• Pipe thread drilled hole sizes
• Unified tap drill size chart (inch)
• Metric tap and drill chart

Tap drill size chart

For a more in-depth understanding on threads, please read our thread design and thread standards articles.

The chart in Table 1 is used for tapping female threads into a component.

1. Identify the screw designation, which correlates with the tap size on the chart.
2. Use the corresponding drill size to drill the hole.

Table 1: Tap drill size chart to tap female threads into a component

TAP SIZE		DRILL SIZE
INCH	METRIC	DRILL SIZE	DECIMAL EQUIVALENT
0-80		3/64	.0469
	M1.6 X 0.35	1.25mm	.0492
	M1.8 X 0.35	1.45mm	.0571
1-64		53	.0595
1-72		53	.0595
	M2 X 0.40	1.60mm	.0630
2-56		50	.0700
2-64		50	.0700
	M2.2 X 0.45	1.75mm	.0689
	M2.5 X 0.45	2.05mm	.0807
3-48		47	.0785
3-56		46	.0810
4-40		43	.0890
4-48		42	.0935
	M3 X 0.50	2.50mm	.0984
5-40		38	.1015
5-44		37	.1040
	M3.5 X 0.60	2.90mm	.1142
6-32		36	.1065
6-40		33	.1130
	M4 X 0.70	3.30mm	.1299
8-32		29	.1360
8-36		29	.1360
	M4.5 X 0.75	3.70mm	.1476
10-24		26	.1470
10-32		21	.1590
	M5 X 0.80	4.20mm	.1654
12-24		16	.1770
12-28		15	.1800
	M6 X 1.00	5.00mm	.1969
1/4-20		7	.2010
1/4-28		3	.2130
	M7 X 1.00	6.00mm	.2362
5/16-18		F	.2570
	M8 X 1.25	6.70mm	.2638
5/16-24		I	.2720
	M8 X 1.0	7.00mm	.2756
3/8-16		5/16	.3125
3/8-24		Q	.3320
	M10 X 1.50	8.50mm	.3346
	M10 X 1.25	8.70mm	.3425
7/16-14		U	.3680
7/16-20		25/64	.3906
	M12 X 1.75	10.20mm	.4016
1/2-13		27/64	.4219
	M12 X 1.25	10.80mm	.4252
	M14 X 2.00	12.00mm	.4224
1/2-20		29/64	.4531
9/16-12		31/64	.4844
9/16-18		33/64	.5156
5/8-11		17/32	.5312
5/8-18		37/64	.5781
	M16 X 2.00	14.00mm	.5512
	M16 X 1.50	14.50mm	.5906
	M18 X 2.50	15.50mm	.6102
	M18 X 1.50	16.50mm	.6496
3/4-10		21/32	.6562
3/4-16		11/16	.6875
	M20 X 2.50	17.50mm	.6890
		45/64	.7031
		23/32	.7188
	M20 X 1.50	18.50mm	.7283
	M22 X 2.50	19.50mm	.7677
	M22 X 1.50	20.50mm	.8071
7/8-9		49/64	.7656
7/8-14		13/16	.8125
	M24 X 3.00	21.00mm	.8268
	M24 X 2.00	22.00mm	.8661
1-8		7/8	.8750
1-12		59/64	.9219
	M27 X 3.00	24.00mm	.9449
	M27 X 2.00	25.00mm	.9843
1-1/8-7		63/64	.9844
	M30 X 3.50	26.50mm	1.0433
1-1/8-12		1-3/64	1.0469
	M30 X 2.00	28.00mm	1.1024
1-1/4-7		1-7/64	1.1094
	M33 X 3.50	29.50mm	1.1614
1-1/4-12		1-11/64	1.1719
1-3/8-6		1-7/32	1.2188
	M33 X 2.00	31.00mm	1.2205
1-3/8-12		1-19/64	1.2969
	M36 X 4.00	32.00mm	1.2598
	M36 X 3.00	33.00mm	1.2992
1-1/2-6		1-11/32	1.3438
	M39 X 4.00	35.00mm	1.3780
1-1/2-12		1-27/64	1.4219
	M39 X 3.00	36.00mm	1.4173

Pipe thread drilled hole sizes

The chart in Table 2 describes how to determine the size of unified male threads when making a bolt or threaded pipe.

1. Use the thread nominal size column to identify the desired thread designation.
2. Based on the desired nominal size, look at the desired standard column to determine the minimum outside diameter of the component for the threads.

Table 2: Chart to determine the size of unified male threads when making a bolt or threaded pipe

	Thread standard/type
Thread Nominal Size	NPT	NPTF	NPSC	NPSM	NPSF	NPSI	BSPT	BSPP
1/16 - 27	D (0.246)	D (0.246)	.250		.250	.250
1/8 - 27	Q (0.332)	Q (0.332)	.3437	.3593	.3437	.3437
1/8 - 28							.3281	.3437
1/4 - 18	.4375	.4375	.4375	.4687	.4375	.4375
1/4 - 19							.4375	.4531
3/8 - 18	.5625	.5781	.5781	.6093	.5781	.5781
3/8 - 19							.5781	.5937
1/2 - 14	.7031	.7031	.7187	.750	.7187	.7187	.7187	.7343
5/8 - 14								.8125
3/4 - 14	.9062	.9218	.9218	.9646			.9380	.9650
7/8 - 14								1.1093
1 - 11							1.1718	1.1875
1 - 11-1/2	1.1406	1.1562	1.1562	1.2031
1-1/4 - 11							1.500	1.5468
1-1/4 - 11-1/2	1.4843	1.500	1.500	1.5468
1-1/2 - 11							1.750	1.7656
1-1/2 - 11-1/2	1.7343	1.7343	1.750	1.7913
1-3/4 - 11								2.000
2 - 11							2.2187	2.250
2 - 11-1/2	2.2031	2.2187	2.2187	2.2638

Unified tap drill size chart (inch)

The chart in Table 3 is for unified gauge threads (inch).

1. Look up the TPI and desired thread percentage to determine the corresponding outer diameter.
   1. TPI means threads-per-inch.
   2. Thread percentage is the percentage of a bolt's shank that has threads.
   3. The recommended thread percentage is 65%, 70%, and 75%.
2. Use the two formulas below to calculate the necessary drilled hole size in inches. For either formula, when inputting thread percentage, use, for example, 65% instead of 0.65.
   1. In the second method, double thread depth means twice the depth of the thread. For example, if the thread depth is .5 millimeters, the double thread depth is 1.0 millimeter.

Method 1 (inch)

Method 2 (inch)

Unified (inch) calculation example

Find the drilled hole size for a 50% thread in a 1/4 inch - 20 TPI tapped hole.

1. Look in the chart's first column for 20 TPI.
2. Match this row with the column for 50% thread percentage.
3. This results in 0.0325.
4. Subtract the result from the outer diameter (0.250).
5. The required diameter of the drilled hole is 0.250 - 0.0325 = 0.2175 inches.

Table 3: Tap drill size chart for unified gauge threads (inch)

Metric tap and drill chart

Table 4 shows the tap and drill chart for Metric threads.

1. Look up the desired pitch and thread percentage to find the corresponding outer diameter.
2. Similar to the unified tap and drill section (see above), use the two formulas below to calculate the necessary size of the drilled hole.
   1. For metric threads, the recommended thread percentages are 65% and 70%.

Method 1

Method 2

Metric calculation example

Find the drilled hole size for a 65% thread on a 4 mm x 1.00 (M4) tapped hole:

1. Look for the 1.00 mm pitch in the chart's first column.
2. Match this row to the 65% thread percentage column.
3. The result is 0.8444.
4. Subtract the result from the thread diameter (4.0 mm)
5. The result is 4.0 mm - 0.8444 mm = 3.1666 mm, which is the necessary diameter for the drilled hole.

Table 4: Tap and drill chart for Metric threads

mm Pitch	Double thread depth	50% THREAD	55% THREAD	60% THREAD	65% THREAD (RECOMMENDED)	70% THREAD (RECOMMENDED)	75% THREAD	80% THREAD	85% THREAD
4.0	5.1963	2.5982	2.8580	3.1178	3.3776	3.6374	3.8972	4.1570	4.4169
3.50	4.5466	2.2733	2.5006	2.7280	2.9553	3.1826	3.4100	3.6373	3.8646
3.00	3.8969	1.9485	2.1433	2.3381	2.5330	2.7278	2.9227	3.1175	3.3124
2.50	3.2476	1.6238	1.7862	1.9486	2.1109	2.2733	2.4357	2.5981	2.7605
2.00	2.5979	1.2990	1.4288	1.5587	1.6886	1.8185	1.9484	2.0783	2.2082
1.75	2.2733	1.1367	1.2503	1.3640	1.4776	1.5913	1.7050	1.8186	1.9323
1.50	1.9487	.9744	1.0718	1.1692	1.2667	1.3641	1.4615	1.5590	1.6564
1.25	1.6236	.8118	.8930	.9742	1.0553	1.1365	1.2177	1.2989	1.3801
1.00	1.2990	.6495	.7145	.7794	.8444	.9093	.9743	1.0392	1.1042
.90	1.1687	.5844	.6428	.7012	.7597	.8181	.8765	.9350	.9934
.80	1.0394	.5197	.5717	.6236	.6756	.7276	.7796	.8315	.8835
.75	.9743	.4871	.5359	.5846	.6333	.6820	.7307	.7794	.8282
.70	.9093	.4547	.5001	.5456	.5910	.6365	.6820	.7274	.7729
.60	.7793	.3897	.4286	.4676	.5065	.5455	.5845	.6234	.6624
.50	.6421	.3211	.3532	.3853	.4174	.4495	.4816	.2137	.5458
.45	.5847	.2924	.3216	.3508	.3801	.4093	.4385	.4678	.4970
.40	.5197	.2599	.2858	.3118	.3378	.3638	.3898	.4158	.4417
.35	.4547	.2274	.2501	.2728	.2956	.3183	.3410	.3638	.3865
.30	.3896	.1948	.2143	.2338	.2532	.2727	.2922	.3117	.3312
.25	.3246	.1663	.1785	.1948	.2110	.2272	.2434	.2597	.2759