Drill Reference Chart

Use the reference chart below to correctly size your holes for drills and hardware.

How to use this chart

Find your drill or hardware thread size. The recommended close/free fit will be the size of your hole. Use the free size for a looser fit and close for a tight fit.

If you are countersinking, the close/free fit sizes will apply to your minor diameter.

Imperial Drill Sizes: Inch

Screw/ Thread Size	Thread Size Examples	Major Diameter	Close/Free Fit
4	4-40	.112″	.117″ – .129″
6	6-32	.138″	.144″ – .150″
8	8-32	.164″	.169″ – .177″
10	10-32	.190″	.196″ – .201″
1/4	1/4-20, 1/4-28	.250″	.257″ – .266″
5/16	5/16-18, 5/16-24	.313″	.323″ – .332″
3/8	3/8-16, 3/8-24	.375″	.386″ – .397″
7/16	7/16-14,7/16-20, 7/16-28	.438″	.453″ – .469″
1/2	1/2-13, 1/2-20, 1/2-28	.500″	.516″ – .533″
9/16	9/16-12, 9/16-18	.556″	.578″ – .594″
5/8	5/8-11, 5/8-18, 5/8-24	.625″	.640″ – .659″
11/16	11/16-18, 11/16-24	.688″	.703″ – .723″
3/4	3/4-10, 3/4-16, 3/4-20	.750″	.766″ – .795″
13/16	13/16-16, 13/16-20	.813″	.828″ – .862″
7/8	7/8-9, 7/8-14, 7/8-20	.875″	.891″ – .925″
15/16	15/16-16, 15/16-20	.938″	.953” – .990″
1	1-8, 1-12	1.000″	1.016″ – 1.1065″

Metric Drill Sizes: Inch

Screw/ Thread Size	Thread Size Examples	Major Diameter	Close/Free Fit
2	M2x0.4	.079″	.087″ – .102″
3	M2.5×0.45	.098″	.106″ – .122″
3	M3x0.5, M3x0.35	.118″	.126″ – .142″
4	M4x0.7, M4x0.5	.157″	.169″ – .189″
5	M5x0.8, M5x0.5	.197″	.209″ – .228″
6	M6x1, M6x0.75	.236″	.252″ – .276″
8	M8x1.25, M8x1.00	.315″	.331″ – .394″
10	M10x1.75, M10x1.5, M10x1	.394″	.413″ – .572″
12	M12x1.75, M12x1.5, M12x1	.472″	.512″ – .591″
14	M14x2, M14x1.5	551″	.591″ – .669″
16	M16x2, M16x1.5	.630″	.669″ – .748″
20	M20x2.5, M20x1.5	.787″	.827″ – .945″
24	M24x3, M24x2	945″	.984″ – 1.102“

Imperial Drill Sizes: MM

Screw/ Thread Size	Thread Size Examples	Major Diameter (MM)	Close/Free Fit (MM)
4	4-40	2.845	2.972 – 3.277
6	6-32	3.505	3.658 – 3.810
8	8-32	4.166	4.293 – 4.496
10	10-32	4.826	4.978 – 5.105
1/4	1/4-20, 1/4-28	6.350	6.528 – 6.756
5/16	5/16-18, 5/16-24	7.950	8.204 – 8.433
3/8	3/8-16, 3/8-24	9.525	9.804 – 10.084
7/16	7/16-14,7/16-20, 7/16-28	11.113	11.506 – 11.913
1/2	1/2-13, 1/2-20, 1/2-28	12.700	13.106 – 13.538
9/16	9/16-12, 9/16-18	14.129	14.684 – 15.083
5/8	5/8-11, 5/8-18, 5/8-24	15.875	16.256 – 16.739
11/16	11/16-18, 11/16-24	17.463	17.859 – 18.364
3/4	3/4-10, 3/4-16, 3/4-20	19.050	19.446 – 20.193
13/16	13/16-16, 13/16-20	20.638	21.034 – 21.895
7/8	7/8-9, 7/8-14, 7/8-20	22.225	22.621 – 23.495
15/16	15/16-16, 15/16-20	23.813	24.209 – 25.146
1	1-8, 1-12	25.400	25.796 – 27.051

Metric Drill Sizes: MM

Screw/ Thread Size	Thread Size Examples	Major Diameter (MM)	Close/Free Fit (MM)
2	M2x0.4	2.0	2.2 – 2.6
2.5	M2.5×0.45	2.5	2.7 – 3.1
3	M3x0.5, M3x0.35	3.0	3.2 – 3.6
4	M4x0.7, M4x0.5	4.0	4.3 – .4.8
5	M5x0.8, M5x0.5	5.0	5.3 – 5.8
6	M6x1, M6x0.75	6.0	6.4 – 7.0
8	M8x1.25, M8x1.00	8.0	8.4 – 10.0
10	M10x1.75, M10x1.5, M10x1	10.0	10.5 – 12.0
12	M12x1.75, M12x1.5, M12x1	12.0	13.0 – 15.0
14	M14x2, M14x1.5	14.0	15.0 – 17.0
16	M16x2, M16x1.5	16.0	17.0 – 19.0
20	M20x2.5, M20x1.5	20.0	21.0 – 24.0
24	M24x3, M24x2	24.0	25.0 – 28.0