M8 × 1.25

Metric Coarse

Standard / Recommended tapping drill6.8 mm≈ 6.8 mm

Drill designation6.8 mmmetric drill

Decimal inches0.267717 inexact conversion

Metric equivalent6.8 mm25.4 mm per inch

Clearance holes — not tapping drillsClose · Normal · Loose

Close fit8.4 mm

Normal fit9 mm

Loose fit10 mm

Major diameter8 mm

Pitch1.25 mm

Threads / inch20.32

Thread form60° · parallel

ISO metric coarse thread. The tapping drill is a recognised cut-tap workshop recommendation.

Custom thread engagementCalculated alternative — never replaces the recognised drill above.

Desired engagement%

Calculated alternative6.863 mmApproximate 60° straight cut-thread geometry

VERIFIED BROWSE TABLE

Thread sizes at a glance.

141 of 141 verified entries shown. Tap any row and the selected result will move into view.

Thread	Standard	Major Ø	Pitch / TPI	Recommended tap drill	Normal clearance
M1.6 × 0.35	Metric Coarse	1.6 mm	0.35 mm	1.25 mm1.25 mm	1.8 mm
M2 × 0.4	Metric Coarse	2 mm	0.4 mm	1.6 mm1.6 mm	2.4 mm
M2.5 × 0.45	Metric Coarse	2.5 mm	0.45 mm	2.05 mm2.05 mm	2.9 mm
M3 × 0.5	Metric Coarse	3 mm	0.5 mm	2.5 mm2.5 mm	3.4 mm
M4 × 0.7	Metric Coarse	4 mm	0.7 mm	3.3 mm3.3 mm	4.5 mm
M5 × 0.8	Metric Coarse	5 mm	0.8 mm	4.2 mm4.2 mm	5.5 mm
M6 × 1	Metric Coarse	6 mm	1 mm	5 mm5 mm	6.6 mm
M8 × 1.25	Metric Coarse	8 mm	1.25 mm	6.8 mm6.8 mm	9 mm
M10 × 1.5	Metric Coarse	10 mm	1.5 mm	8.5 mm8.5 mm	11 mm
M12 × 1.75	Metric Coarse	12 mm	1.75 mm	10.2 mm10.2 mm	13.5 mm
M14 × 2	Metric Coarse	14 mm	2 mm	12 mm12 mm	15.5 mm
M16 × 2	Metric Coarse	16 mm	2 mm	14 mm14 mm	17.5 mm
M18 × 2.5	Metric Coarse	18 mm	2.5 mm	15.5 mm15.5 mm	20 mm
M20 × 2.5	Metric Coarse	20 mm	2.5 mm	17.5 mm17.5 mm	22 mm
M22 × 2.5	Metric Coarse	22 mm	2.5 mm	19.5 mm19.5 mm	24 mm
M24 × 3	Metric Coarse	24 mm	3 mm	21 mm21 mm	26 mm
M27 × 3	Metric Coarse	27 mm	3 mm	24 mm24 mm	30 mm
M30 × 3.5	Metric Coarse	30 mm	3.5 mm	26.5 mm26.5 mm	33 mm
M33 × 3.5	Metric Coarse	33 mm	3.5 mm	29.5 mm29.5 mm	36 mm
M36 × 4	Metric Coarse	36 mm	4 mm	32 mm32 mm	39 mm
M8 × 1	Metric Fine	8 mm	1 mm	7 mm7 mm	9 mm
M10 × 1	Metric Fine	10 mm	1 mm	9 mm9 mm	11 mm
M10 × 1.25	Metric Fine	10 mm	1.25 mm	8.8 mm8.8 mm	11 mm
M12 × 1.25	Metric Fine	12 mm	1.25 mm	10.8 mm10.8 mm	13.5 mm
M12 × 1.5	Metric Fine	12 mm	1.5 mm	10.5 mm10.5 mm	13.5 mm
M14 × 1.5	Metric Fine	14 mm	1.5 mm	12.5 mm12.5 mm	15.5 mm
M16 × 1.5	Metric Fine	16 mm	1.5 mm	14.5 mm14.5 mm	17.5 mm
M18 × 1.5	Metric Fine	18 mm	1.5 mm	16.5 mm16.5 mm	20 mm
M18 × 2	Metric Fine	18 mm	2 mm	16 mm16 mm	20 mm
M20 × 1.5	Metric Fine	20 mm	1.5 mm	18.5 mm18.5 mm	22 mm
M20 × 2	Metric Fine	20 mm	2 mm	18 mm18 mm	22 mm
M22 × 1.5	Metric Fine	22 mm	1.5 mm	20.5 mm20.5 mm	24 mm
M22 × 2	Metric Fine	22 mm	2 mm	20 mm20 mm	24 mm
M24 × 2	Metric Fine	24 mm	2 mm	22 mm22 mm	26 mm
M27 × 2	Metric Fine	27 mm	2 mm	25 mm25 mm	30 mm
M30 × 2	Metric Fine	30 mm	2 mm	28 mm28 mm	33 mm
M33 × 2	Metric Fine	33 mm	2 mm	31 mm31 mm	36 mm
M36 × 3	Metric Fine	36 mm	3 mm	33 mm33 mm	39 mm
#2-56 UNC	UNC	2.184 mm	56 TPI · 0.454 mm	#501.778 mm	—
#3-48 UNC	UNC	2.515 mm	48 TPI · 0.529 mm	#471.994 mm	—
#4-40 UNC	UNC	2.845 mm	40 TPI · 0.635 mm	#432.261 mm	—
#5-40 UNC	UNC	3.175 mm	40 TPI · 0.635 mm	#382.578 mm	—
#6-32 UNC	UNC	3.505 mm	32 TPI · 0.794 mm	#362.705 mm	—
#8-32 UNC	UNC	4.166 mm	32 TPI · 0.794 mm	#293.454 mm	—
#10-24 UNC	UNC	4.826 mm	24 TPI · 1.058 mm	#253.797 mm	—
#12-24 UNC	UNC	5.486 mm	24 TPI · 1.058 mm	#164.496 mm	—
1/4-20 UNC	UNC	6.35 mm	20 TPI · 1.27 mm	#75.105 mm	—
5/16-18 UNC	UNC	7.938 mm	18 TPI · 1.411 mm	F6.528 mm	—
3/8-16 UNC	UNC	9.525 mm	16 TPI · 1.588 mm	5/167.938 mm	—
7/16-14 UNC	UNC	11.113 mm	14 TPI · 1.814 mm	U9.347 mm	—
1/2-13 UNC	UNC	12.7 mm	13 TPI · 1.954 mm	27/6410.716 mm	—
9/16-12 UNC	UNC	14.288 mm	12 TPI · 2.117 mm	31/6412.303 mm	—
5/8-11 UNC	UNC	15.875 mm	11 TPI · 2.309 mm	17/3213.494 mm	—
3/4-10 UNC	UNC	19.05 mm	10 TPI · 2.54 mm	21/3216.669 mm	—
7/8-9 UNC	UNC	22.225 mm	9 TPI · 2.822 mm	49/6419.447 mm	—
1-8 UNC	UNC	25.4 mm	8 TPI · 3.175 mm	7/822.225 mm	—
#2-64 UNF	UNF	2.184 mm	64 TPI · 0.397 mm	#501.778 mm	—
#3-56 UNF	UNF	2.515 mm	56 TPI · 0.454 mm	#452.083 mm	—
#4-48 UNF	UNF	2.845 mm	48 TPI · 0.529 mm	#422.375 mm	—
#5-44 UNF	UNF	3.175 mm	44 TPI · 0.577 mm	#372.642 mm	—
#6-40 UNF	UNF	3.505 mm	40 TPI · 0.635 mm	#332.87 mm	—
#8-36 UNF	UNF	4.166 mm	36 TPI · 0.706 mm	#293.454 mm	—
#10-32 UNF	UNF	4.826 mm	32 TPI · 0.794 mm	#214.039 mm	—
#12-28 UNF	UNF	5.486 mm	28 TPI · 0.907 mm	#144.623 mm	—
1/4-28 UNF	UNF	6.35 mm	28 TPI · 0.907 mm	#35.41 mm	—
5/16-24 UNF	UNF	7.938 mm	24 TPI · 1.058 mm	I6.909 mm	—
3/8-24 UNF	UNF	9.525 mm	24 TPI · 1.058 mm	Q8.433 mm	—
7/16-20 UNF	UNF	11.113 mm	20 TPI · 1.27 mm	25/649.922 mm	—
1/2-20 UNF	UNF	12.7 mm	20 TPI · 1.27 mm	29/6411.509 mm	—
9/16-18 UNF	UNF	14.288 mm	18 TPI · 1.411 mm	33/6413.097 mm	—
5/8-18 UNF	UNF	15.875 mm	18 TPI · 1.411 mm	37/6414.684 mm	—
3/4-16 UNF	UNF	19.05 mm	16 TPI · 1.588 mm	11/1617.463 mm	—
7/8-14 UNF	UNF	22.225 mm	14 TPI · 1.814 mm	13/1620.638 mm	—
1-12 UNF	UNF	25.4 mm	12 TPI · 2.117 mm	59/6423.416 mm	—
1/4-32 UNEF	UNEF	6.35 mm	32 TPI · 0.794 mm	5.6 mm5.6 mm	—
5/16-32 UNEF	UNEF	7.938 mm	32 TPI · 0.794 mm	7.1 mm7.1 mm	—
3/8-32 UNEF	UNEF	9.525 mm	32 TPI · 0.794 mm	8.7 mm8.7 mm	—
7/16-28 UNEF	UNEF	11.113 mm	28 TPI · 0.907 mm	10.2 mm10.2 mm	—
1/2-28 UNEF	UNEF	12.7 mm	28 TPI · 0.907 mm	11.8 mm11.8 mm	—
9/16-24 UNEF	UNEF	14.288 mm	24 TPI · 1.058 mm	13.2 mm13.2 mm	—
5/8-24 UNEF	UNEF	15.875 mm	24 TPI · 1.058 mm	14.8 mm14.8 mm	—
3/4-20 UNEF	UNEF	19.05 mm	20 TPI · 1.27 mm	17.8 mm17.8 mm	—
7/8-20 UNEF	UNEF	22.225 mm	20 TPI · 1.27 mm	21 mm21 mm	—
1-20 UNEF	UNEF	25.4 mm	20 TPI · 1.27 mm	24.1 mm24.1 mm	—
1/8-40 BSW	BSW	3.175 mm	40 TPI · 0.635 mm	2.5 mm2.5 mm	—
5/32-32 BSW	BSW	3.969 mm	32 TPI · 0.794 mm	3.1 mm3.1 mm	—
3/16-24 BSW	BSW	4.763 mm	24 TPI · 1.058 mm	3.6 mm3.6 mm	—
7/32-24 BSW	BSW	5.556 mm	24 TPI · 1.058 mm	4.5 mm4.5 mm	—
1/4-20 BSW	BSW	6.35 mm	20 TPI · 1.27 mm	5 mm5 mm	—
5/16-18 BSW	BSW	7.938 mm	18 TPI · 1.411 mm	6.5 mm6.5 mm	—
3/8-16 BSW	BSW	9.525 mm	16 TPI · 1.588 mm	7.9 mm7.9 mm	—
7/16-14 BSW	BSW	11.113 mm	14 TPI · 1.814 mm	9.2 mm9.2 mm	—
1/2-12 BSW	BSW	12.7 mm	12 TPI · 2.117 mm	10.5 mm10.5 mm	—
9/16-12 BSW	BSW	14.288 mm	12 TPI · 2.117 mm	12 mm12 mm	—
5/8-11 BSW	BSW	15.875 mm	11 TPI · 2.309 mm	13.4 mm13.4 mm	—
3/4-10 BSW	BSW	19.05 mm	10 TPI · 2.54 mm	16.4 mm16.4 mm	—
7/8-9 BSW	BSW	22.225 mm	9 TPI · 2.822 mm	19.25 mm19.25 mm	—
1-8 BSW	BSW	25.4 mm	8 TPI · 3.175 mm	22 mm22 mm	—
3/16-32 BSF	BSF	4.763 mm	32 TPI · 0.794 mm	4 mm4 mm	—
7/32-28 BSF	BSF	5.556 mm	28 TPI · 0.907 mm	4.6 mm4.6 mm	—
1/4-26 BSF	BSF	6.35 mm	26 TPI · 0.977 mm	5.3 mm5.3 mm	—
5/16-22 BSF	BSF	7.938 mm	22 TPI · 1.155 mm	6.7 mm6.7 mm	—
3/8-20 BSF	BSF	9.525 mm	20 TPI · 1.27 mm	8.2 mm8.2 mm	—
7/16-18 BSF	BSF	11.113 mm	18 TPI · 1.411 mm	9.6 mm9.6 mm	—
1/2-16 BSF	BSF	12.7 mm	16 TPI · 1.588 mm	11 mm11 mm	—
9/16-16 BSF	BSF	14.288 mm	16 TPI · 1.588 mm	12.6 mm12.6 mm	—
5/8-14 BSF	BSF	15.875 mm	14 TPI · 1.814 mm	14 mm14 mm	—
3/4-12 BSF	BSF	19.05 mm	12 TPI · 2.117 mm	16.8 mm16.8 mm	—
7/8-11 BSF	BSF	22.225 mm	11 TPI · 2.309 mm	19.75 mm19.75 mm	—
1-10 BSF	BSF	25.4 mm	10 TPI · 2.54 mm	22.75 mm22.75 mm	—
G 1/16 BSPPNominal 1/16 in	BSPP / G — Parallel	7.723 mm	28 TPI · 0.907 mm	6.8 mm6.8 mm	—
G 1/8 BSPPNominal 1/8 in	BSPP / G — Parallel	9.728 mm	28 TPI · 0.907 mm	8.8 mm8.8 mm	—
G 1/4 BSPPNominal 1/4 in	BSPP / G — Parallel	13.157 mm	19 TPI · 1.337 mm	11.8 mm11.8 mm	—
G 3/8 BSPPNominal 3/8 in	BSPP / G — Parallel	16.662 mm	19 TPI · 1.337 mm	15.25 mm15.25 mm	—
G 1/2 BSPPNominal 1/2 in	BSPP / G — Parallel	20.955 mm	14 TPI · 1.814 mm	19 mm19 mm	—
G 5/8 BSPPNominal 5/8 in	BSPP / G — Parallel	22.911 mm	14 TPI · 1.814 mm	21 mm21 mm	—
G 3/4 BSPPNominal 3/4 in	BSPP / G — Parallel	26.441 mm	14 TPI · 1.814 mm	24.5 mm24.5 mm	—
G 1 BSPPNominal 1 in	BSPP / G — Parallel	33.249 mm	11 TPI · 2.309 mm	30.75 mm30.75 mm	—
G 1 1/4 BSPPNominal 1 1/4 in	BSPP / G — Parallel	41.91 mm	11 TPI · 2.309 mm	39.5 mm39.5 mm	—
G 1 1/2 BSPPNominal 1 1/2 in	BSPP / G — Parallel	47.803 mm	11 TPI · 2.309 mm	45.25 mm45.25 mm	—
G 2 BSPPNominal 2 in	BSPP / G — Parallel	59.614 mm	11 TPI · 2.309 mm	57 mm57 mm	—
Rc 1/16 BSPTNominal 1/16 in	BSPT / Rc — Tapered	7.723 mm	28 TPI · 0.907 mm	6.3 mm6.3 mm	—
Rc 1/8 BSPTNominal 1/8 in	BSPT / Rc — Tapered	9.728 mm	28 TPI · 0.907 mm	8.4 mm8.4 mm	—
Rc 1/4 BSPTNominal 1/4 in	BSPT / Rc — Tapered	13.157 mm	19 TPI · 1.337 mm	10.8 mm10.8 mm	—
Rc 3/8 BSPTNominal 3/8 in	BSPT / Rc — Tapered	16.662 mm	19 TPI · 1.337 mm	14.5 mm14.5 mm	—
Rc 1/2 BSPTNominal 1/2 in	BSPT / Rc — Tapered	20.955 mm	14 TPI · 1.814 mm	18 mm18 mm	—
Rc 5/8 BSPTNominal 5/8 in	BSPT / Rc — Tapered	22.911 mm	14 TPI · 1.814 mm	Awaiting verification	—
Rc 3/4 BSPTNominal 3/4 in	BSPT / Rc — Tapered	26.441 mm	14 TPI · 1.814 mm	23 mm23 mm	—
Rc 1 BSPTNominal 1 in	BSPT / Rc — Tapered	33.249 mm	11 TPI · 2.309 mm	29 mm29 mm	—
Rc 1 1/4 BSPTNominal 1 1/4 in	BSPT / Rc — Tapered	41.91 mm	11 TPI · 2.309 mm	38 mm38 mm	—
Rc 1 1/2 BSPTNominal 1 1/2 in	BSPT / Rc — Tapered	47.803 mm	11 TPI · 2.309 mm	44 mm44 mm	—
Rc 2 BSPTNominal 2 in	BSPT / Rc — Tapered	59.614 mm	11 TPI · 2.309 mm	55 mm55 mm	—
1/8-27 NPTNominal 1/8 in	NPT — Tapered pipe thread	10.389 mm	27 TPI · 0.941 mm	21/648.334 mm	—
1/4-18 NPTNominal 1/4 in	NPT — Tapered pipe thread	13.741 mm	18 TPI · 1.411 mm	7/1611.113 mm	—
3/8-18 NPTNominal 3/8 in	NPT — Tapered pipe thread	17.221 mm	18 TPI · 1.411 mm	9/1614.288 mm	—
1/2-14 NPTNominal 1/2 in	NPT — Tapered pipe thread	21.438 mm	14 TPI · 1.814 mm	45/6417.859 mm	—
3/4-14 NPTNominal 3/4 in	NPT — Tapered pipe thread	26.772 mm	14 TPI · 1.814 mm	29/3223.019 mm	—
1-11.5 NPTNominal 1 in	NPT — Tapered pipe thread	33.477 mm	11.5 TPI · 2.209 mm	1 9/6428.972 mm	—
1 1/4-11.5 NPTNominal 1 1/4 in	NPT — Tapered pipe thread	42.24 mm	11.5 TPI · 2.209 mm	1 31/6437.703 mm	—
1 1/2-11.5 NPTNominal 1 1/2 in	NPT — Tapered pipe thread	48.311 mm	11.5 TPI · 2.209 mm	1 47/6444.053 mm	—
2-11.5 NPTNominal 2 in	NPT — Tapered pipe thread	60.35 mm	11.5 TPI · 2.209 mm	2 13/6455.959 mm	—

DATA & SAFE USE

Verified before displayed.

141 thread entries are held in a separate structured dataset so dimensions, sources and future fields can be reviewed without rewriting the interface.

Recommendation, not guesswork.

Thread standards define the thread geometry. The displayed tapping drills come from established tap and drill manufacturers and remain identified as workshop recommendations.

Kept separate.

Close, normal and loose metric clearance holes use the ISO 273 series. They never replace the tapping drill. Unverified clearance series are left unavailable.

Nominal is not actual.

BSP and NPT nominal pipe sizes are shown separately from the real reference diameter. BSPP is parallel; BSPT and NPT are tapered and stay clearly distinguished.

Secondary by design.

The optional calculation is limited to straight 60° cut threads. It is disabled for Whitworth-form and tapered pipe threads where the simple approximation is unsuitable.

Primary standards & technical references

Use the links below to review the standard scope and manufacturer drill guidance behind the published values.

Workshop reference

Starting values only. Confirm critical, pressure-retaining, safety-related or close-tolerance work against the current thread standard, the specific tap manufacturer, material, hole depth and gauging requirements.

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