Threads / Find · identify · prepare

Thread size charts & tap drills.

Find nominal thread diameters and pitches, identify an unknown thread or check a tapping drill. Keep the exact designation and tap type with the result.

111 nominal sizes5 thread series66 source-chart rows

Start with what you know

Three ways to find your answer.

01 / KNOWN SIZE

I have a thread designation

Find nominal dimensions, compare the nearby pitch and check the source.

Look up my size →

02 / UNKNOWN SIZE

I have a part to identify

Check the thread shape, measure the outside diameter and narrow by pitch.

Identify from measurements →

03 / PREPARE A HOLE

I need a tapping drill

Separate cutting from forming, and compare source values with the sizing equation.

Find a tap drill →

Browse by thread series

20 SIZES

Metric coarse

Metric diameters with coarse pitches.

Browse sizes →

24 SIZES

Metric fine

Compare multiple fine pitches at a given diameter.

Browse sizes →

25 SIZES

UNC

Unified coarse threads, including numbered screws.

Browse sizes →

24 SIZES

UNF

Unified fine threads, including numbered screws.

Browse sizes →

18 SIZES

UNEF

Unified extra-fine nominal sizes; no reviewed drill rows.

Browse sizes →

Look up a designation

Series

M10x1.5 Metric coarse →1/4-28 UNF →5/8-11 UNC →#8-32 UNC →

Swipe to see all columns →

Nominal thread sizes in this reference
Designation	Major Ø · in / mm	TPI	Pitch · mm	Drill evidence	Next step
M1.6x0.35 Metric coarse	0.062992 / 1.6	72.571429 converted	0.35	Chart row	Tap-drill lookup →
M2x0.4 Metric coarse	0.07874 / 2	63.5 converted	0.4	Chart row	Tap-drill lookup →
M2.5x0.45 Metric coarse	0.098425 / 2.5	56.444444 converted	0.45	Chart row	Tap-drill lookup →
M3x0.5 Metric coarse	0.11811 / 3	50.8 converted	0.5	Chart row	Tap-drill lookup →
M4x0.7 Metric coarse	0.15748 / 4	36.285714 converted	0.7	Chart row	Tap-drill lookup →
M5x0.8 Metric coarse	0.19685 / 5	31.75 converted	0.8	Chart row	Tap-drill lookup →
M6x1 Metric coarse	0.23622 / 6	25.4 converted	1	Chart row	Tap-drill lookup →
M8x1.25 Metric coarse	0.314961 / 8	20.32 converted	1.25	Chart row	Tap-drill lookup →
M10x1.5 Metric coarse	0.393701 / 10	16.933333 converted	1.5	Chart row	Tap-drill lookup →
M12x1.75 Metric coarse	0.472441 / 12	14.514286 converted	1.75	Chart row	Tap-drill lookup →
M14x2 Metric coarse	0.551181 / 14	12.7 converted	2	Chart row	Tap-drill lookup →
M16x2 Metric coarse	0.629921 / 16	12.7 converted	2	Chart row	Tap-drill lookup →
M20x2.5 Metric coarse	0.787402 / 20	10.16 converted	2.5	Chart row	Tap-drill lookup →
M24x3 Metric coarse	0.944882 / 24	8.466667 converted	3	Chart row	Tap-drill lookup →
M30x3.5 Metric coarse	1.181102 / 30	7.257143 converted	3.5	Equation only	Tap-drill lookup →
M36x4 Metric coarse	1.417323 / 36	6.35 converted	4	Equation only	Tap-drill lookup →
M42x4.5 Metric coarse	1.653543 / 42	5.644444 converted	4.5	Equation only	Tap-drill lookup →
M48x5 Metric coarse	1.889764 / 48	5.08 converted	5	Equation only	Tap-drill lookup →
M56x5.5 Metric coarse	2.204724 / 56	4.618182 converted	5.5	Equation only	Tap-drill lookup →
M64x6 Metric coarse	2.519685 / 64	4.233333 converted	6	Equation only	Tap-drill lookup →
M3x0.35 Metric fine	0.11811 / 3	72.571429 converted	0.35	Chart row	Tap-drill lookup →
M4x0.5 Metric fine	0.15748 / 4	50.8 converted	0.5	Chart row	Tap-drill lookup →
M5x0.5 Metric fine	0.19685 / 5	50.8 converted	0.5	Chart row	Tap-drill lookup →
M6x0.75 Metric fine	0.23622 / 6	33.866667 converted	0.75	Chart row	Tap-drill lookup →
M8x1 Metric fine	0.314961 / 8	25.4 converted	1	Chart row	Tap-drill lookup →
M10x1 Metric fine	0.393701 / 10	25.4 converted	1	Chart row	Tap-drill lookup →
M10x1.25 Metric fine	0.393701 / 10	20.32 converted	1.25	Chart row	Tap-drill lookup →
M12x1.25 Metric fine	0.472441 / 12	20.32 converted	1.25	Equation only	Tap-drill lookup →
M12x1.5 Metric fine	0.472441 / 12	16.933333 converted	1.5	Chart row	Tap-drill lookup →
M14x1.5 Metric fine	0.551181 / 14	16.933333 converted	1.5	Chart row	Tap-drill lookup →
M16x1.5 Metric fine	0.629921 / 16	16.933333 converted	1.5	Chart row	Tap-drill lookup →
M18x1.5 Metric fine	0.708661 / 18	16.933333 converted	1.5	Chart row	Tap-drill lookup →
M18x2 Metric fine	0.708661 / 18	12.7 converted	2	Equation only	Tap-drill lookup →
M20x1.5 Metric fine	0.787402 / 20	16.933333 converted	1.5	Chart row	Tap-drill lookup →
M20x2 Metric fine	0.787402 / 20	12.7 converted	2	Equation only	Tap-drill lookup →
M22x2 Metric fine	0.866142 / 22	12.7 converted	2	Equation only	Tap-drill lookup →
M24x2 Metric fine	0.944882 / 24	12.7 converted	2	Chart row	Tap-drill lookup →
M27x2 Metric fine	1.062992 / 27	12.7 converted	2	Equation only	Tap-drill lookup →
M30x2 Metric fine	1.181102 / 30	12.7 converted	2	Equation only	Tap-drill lookup →
M33x2 Metric fine	1.299213 / 33	12.7 converted	2	Equation only	Tap-drill lookup →
M36x3 Metric fine	1.417323 / 36	8.466667 converted	3	Equation only	Tap-drill lookup →
M39x3 Metric fine	1.535433 / 39	8.466667 converted	3	Equation only	Tap-drill lookup →
M42x3 Metric fine	1.653543 / 42	8.466667 converted	3	Equation only	Tap-drill lookup →
M48x3 Metric fine	1.889764 / 48	8.466667 converted	3	Equation only	Tap-drill lookup →
#1-64 UNC	0.073 / 1.8542	64	0.396875	Chart row	Tap-drill lookup →
#2-56 UNC	0.086 / 2.1844	56	0.453571	Chart row	Tap-drill lookup →
#3-48 UNC	0.099 / 2.5146	48	0.529167	Chart row	Tap-drill lookup →
#4-40 UNC	0.112 / 2.8448	40	0.635	Chart row	Tap-drill lookup →
#5-40 UNC	0.125 / 3.175	40	0.635	Chart row	Tap-drill lookup →
#6-32 UNC	0.138 / 3.5052	32	0.79375	Chart row	Tap-drill lookup →
#8-32 UNC	0.164 / 4.1656	32	0.79375	Chart row	Tap-drill lookup →
#10-24 UNC	0.19 / 4.826	24	1.058333	Chart row	Tap-drill lookup →
#12-24 UNC	0.216 / 5.4864	24	1.058333	Chart row	Tap-drill lookup →
1/4-20 UNC	0.25 / 6.35	20	1.27	Chart row	Tap-drill lookup →
5/16-18 UNC	0.3125 / 7.9375	18	1.411111	Chart row	Tap-drill lookup →
3/8-16 UNC	0.375 / 9.525	16	1.5875	Chart row	Tap-drill lookup →
7/16-14 UNC	0.4375 / 11.1125	14	1.814286	Chart row	Tap-drill lookup →
1/2-13 UNC	0.5 / 12.7	13	1.953846	Chart row	Tap-drill lookup →
9/16-12 UNC	0.5625 / 14.2875	12	2.116667	Chart row	Tap-drill lookup →
5/8-11 UNC	0.625 / 15.875	11	2.309091	Chart row	Tap-drill lookup →
3/4-10 UNC	0.75 / 19.05	10	2.54	Chart row	Tap-drill lookup →
7/8-9 UNC	0.875 / 22.225	9	2.822222	Chart row	Tap-drill lookup →
1-8 UNC	1 / 25.4	8	3.175	Chart row	Tap-drill lookup →
1 1/8-7 UNC	1.125 / 28.575	7	3.628571	Equation only	Tap-drill lookup →
1 1/4-7 UNC	1.25 / 31.75	7	3.628571	Equation only	Tap-drill lookup →
1 3/8-6 UNC	1.375 / 34.925	6	4.233333	Equation only	Tap-drill lookup →
1 1/2-6 UNC	1.5 / 38.1	6	4.233333	Equation only	Tap-drill lookup →
1 3/4-5 UNC	1.75 / 44.45	5	5.08	Equation only	Tap-drill lookup →
2-4 1/2 UNC	2 / 50.8	4.5	5.644444	Equation only	Tap-drill lookup →
#0-80 UNF	0.06 / 1.524	80	0.3175	Chart row	Tap-drill lookup →
#1-72 UNF	0.073 / 1.8542	72	0.352778	Chart row	Tap-drill lookup →
#2-64 UNF	0.086 / 2.1844	64	0.396875	Chart row	Tap-drill lookup →
#3-56 UNF	0.099 / 2.5146	56	0.453571	Chart row	Tap-drill lookup →
#4-48 UNF	0.112 / 2.8448	48	0.529167	Chart row	Tap-drill lookup →
#5-44 UNF	0.125 / 3.175	44	0.577273	Chart row	Tap-drill lookup →
#6-40 UNF	0.138 / 3.5052	40	0.635	Chart row	Tap-drill lookup →
#8-36 UNF	0.164 / 4.1656	36	0.705556	Chart row	Tap-drill lookup →
#10-32 UNF	0.19 / 4.826	32	0.79375	Chart row	Tap-drill lookup →
#12-28 UNF	0.216 / 5.4864	28	0.907143	Chart row	Tap-drill lookup →
1/4-28 UNF	0.25 / 6.35	28	0.907143	Chart row	Tap-drill lookup →
5/16-24 UNF	0.3125 / 7.9375	24	1.058333	Chart row	Tap-drill lookup →
3/8-24 UNF	0.375 / 9.525	24	1.058333	Chart row	Tap-drill lookup →
7/16-20 UNF	0.4375 / 11.1125	20	1.27	Chart row	Tap-drill lookup →
1/2-20 UNF	0.5 / 12.7	20	1.27	Chart row	Tap-drill lookup →
9/16-18 UNF	0.5625 / 14.2875	18	1.411111	Chart row	Tap-drill lookup →
5/8-18 UNF	0.625 / 15.875	18	1.411111	Chart row	Tap-drill lookup →
3/4-16 UNF	0.75 / 19.05	16	1.5875	Chart row	Tap-drill lookup →
7/8-14 UNF	0.875 / 22.225	14	1.814286	Chart row	Tap-drill lookup →
1-12 UNF	1 / 25.4	12	2.116667	Chart row	Tap-drill lookup →
1 1/8-12 UNF	1.125 / 28.575	12	2.116667	Equation only	Tap-drill lookup →
1 1/4-12 UNF	1.25 / 31.75	12	2.116667	Equation only	Tap-drill lookup →
1 3/8-12 UNF	1.375 / 34.925	12	2.116667	Equation only	Tap-drill lookup →
1 1/2-12 UNF	1.5 / 38.1	12	2.116667	Equation only	Tap-drill lookup →
1/4-32 UNEF	0.25 / 6.35	32	0.79375	Maker data needed	Tap-drill lookup →
5/16-32 UNEF	0.3125 / 7.9375	32	0.79375	Maker data needed	Tap-drill lookup →
3/8-32 UNEF	0.375 / 9.525	32	0.79375	Maker data needed	Tap-drill lookup →
7/16-28 UNEF	0.4375 / 11.1125	28	0.907143	Maker data needed	Tap-drill lookup →
1/2-28 UNEF	0.5 / 12.7	28	0.907143	Maker data needed	Tap-drill lookup →
9/16-24 UNEF	0.5625 / 14.2875	24	1.058333	Maker data needed	Tap-drill lookup →
5/8-24 UNEF	0.625 / 15.875	24	1.058333	Maker data needed	Tap-drill lookup →
11/16-24 UNEF	0.6875 / 17.4625	24	1.058333	Maker data needed	Tap-drill lookup →
3/4-20 UNEF	0.75 / 19.05	20	1.27	Maker data needed	Tap-drill lookup →
13/16-20 UNEF	0.8125 / 20.6375	20	1.27	Maker data needed	Tap-drill lookup →
7/8-20 UNEF	0.875 / 22.225	20	1.27	Maker data needed	Tap-drill lookup →
1-20 UNEF	1 / 25.4	20	1.27	Maker data needed	Tap-drill lookup →
1 1/16-18 UNEF	1.0625 / 26.9875	18	1.411111	Maker data needed	Tap-drill lookup →
1 1/8-18 UNEF	1.125 / 28.575	18	1.411111	Maker data needed	Tap-drill lookup →
1 3/16-18 UNEF	1.1875 / 30.1625	18	1.411111	Maker data needed	Tap-drill lookup →
1 1/4-18 UNEF	1.25 / 31.75	18	1.411111	Maker data needed	Tap-drill lookup →
1 3/8-18 UNEF	1.375 / 34.925	18	1.411111	Maker data needed	Tap-drill lookup →
1 1/2-18 UNEF	1.5 / 38.1	18	1.411111	Maker data needed	Tap-drill lookup →

Read a complete designation

Understand metric and inch callouts, pitch, class and handedness.

Dimensions & lead calculator

Convert pitch and calculate explicitly defined basic geometry.

Read a tolerance class

Separate nominal dimensions from manufacturing acceptance limits.

Evidence and boundaries

What has been checked?

Reviewed 2026-10-19. 66 matching chart rows and the metric/UNC/UNF equations were read directly. The other 27 metric/UNC/UNF sizes have equation estimates only; 18 UNEF sizes have no reviewed drill selection. Calculated conversions are labelled; class-specific manufacturing limits are not supplied.

ISO 261 · metric general plan ↗

Public scope only. Nominal sizes are transcribed from the live directory and checked against their designations; paid standard tables were not reviewed.

ISO 965-1:2026 · tolerance principles ↗

Current public listing, published April 2026. No class-specific limits are reproduced from the paid standard.

Guhring · Tap Drill Sizes ↗

PDF page 2: 66 matched metric and UNC/UNF rows, CUT TAPS and FORM TAPS columns (55%, 65%, 75%), sizing equations and drilling-runout note. Page 1: numbered and letter drill diameters. Publication revision is not printed on this chart.

ASME B1.1 · standard scope ↗

Public product page lists B1.1-2024 and its scope. The paid standard tables have not been reviewed here; this reference does not publish class-specific acceptance limits.

Swagelok · thread identification procedure ↗

Measure at more than one axial position to distinguish taper, then check pitch and thread form. This supports the measurement procedure, not identification from a nominal match.

NBS Handbook 28 · 1963 supplement ↗

Historical nominal designation #8 / 0.164 in only. No historical tolerances are used as current acceptance limits.

Metric designations state diameter and pitch in mm. Fractional inch diameters are evaluated exactly; numbered diameters are nominal size values. Inch pitch is 1/TPI in. Metric values use exactly 25.4 mm/in, with display rounding to six decimal places. The reference chart is a general starting point, not a selected tap’s product specification.