Tap Drill Size Chart

M22 x 2.5 Tap Drill Size

Tap drill

19.5 mm 0.7677 in

Use a 19.5 mm drill (0.7677 in) for 77.0% thread.

Fine thread M22 x 2? Use 20 mm. (0.7874 in, 77.0% thread)

The drill size for a M22 x 2.5 tap is 19.5 mm (0.7677 in). If you are wondering what size drill bit a M22 x 2.5 tap needs, that is the one: it leaves 77.0% of thread, which is the figure standard tap and drill charts are built around. Below are the other holes you might want for this size - a larger drill for tough material, the form-tap hole, and the clearance holes for the bolt that goes in.

Every drill for M22 x 2.5

Tap drills and clearance drills for M22 x 2.5 (Metric coarse, 2.5 mm pitch). Percent of thread is the figure stored for each drill, which reproduces from the major diameter and pitch of M22 x 2.5.
Use Drill Decimal in mm % thread
Standard tap drill Cut tap, general use (D - P) 19.5 mm 0.7677 19.50 77.0%
Inch substitute Closest inch drill if you have no metric set 49/64″ 0.7656 19.45 78.6%
Hard material Stainless, tool steel, anything that fights the tap 20 mm 0.7874 20.00 61.6%
Form (roll) tap Theoretical 20.9 mm - starting point, check your tap maker's chart 21 mm 0.8268 21.00 —

Clearance holes for a M22 x 2.5 bolt

A clearance hole is not tapped. It is the hole in the part the bolt passes through, so it is always larger than the thread.

Clearance holes for M22 x 2.5 per ISO 273. Clearance depends on the bolt diameter alone, so every M22 thread shares these figures.
Fit Hole mm Hole in
Fine 23.00 0.9055
Medium 24.00 0.9449
Coarse 26.00 1.0236

M22 x 2.5 dimensions

Nominal dimensions for M22 x 2.5. The basic internal minor diameter is the hole a 100% thread would start from, which is why no tap drill is ever that small.
Dimension Inch mm
Major diameter 0.8661 22.00
Basic internal minor diameter 0.7596 19.29
Pitch 0.0984 2.50
Thread designation M22 x 2.5

What the hole looks like

Cross-section of a M22 x 2.5 tapped hole, drawn to scale The drilled hole is 19.5 mm, 0.7677 inches or 19.50 millimetres across. The tap cuts outward from that wall to the major diameter of 0.8661 inches. A 100 percent thread would reach in to the basic minor diameter of 0.7596 inches, shown as a dashed line; the difference is why this drill gives 77.0% of thread. major 22 mm drill 19.5 mm · 19.5 mm dashed = 100% thread at 19.29 mm
M22 x 2.5 in section, to scale. The accent line is the thread the tap cuts from a 19.5 mm hole; the dashed line is where the crest would sit at 100% thread. The gap between them is the 23.0% of thread this drill leaves behind.

Work out a different hole for M22 x 2.5

Pre-filled with M22 x 2.5. Change the material, the tap type, or which drills you actually own, and it picks the closest real drill and tells you the percent of thread you end up with. The tables above are the published figures and do not depend on this.

The general-purpose target

Tap type
Drills you have

Best drill you have, cut tap, 70% target

19.7 mm0.7756 in70.8% thread

Theoretical hole 19.73 mm

One size down, deeper thread19.6 mm 0.7717 in · 73.9%

One size up, easier tapping19.8 mm 0.7795 in · 67.7%

For comparison, the published chart drill for M22 x 2.5 is 19.5 mm at 77.0% thread.

Notes on M22 x 2.5

Coarse pitch
M22 x 2.5 is the coarse pitch at 22 mm. It is the usual choice for general work, and it tolerates a slightly off-size hole better than the finer pitches do. Finer options at the same diameter: M22 x 2, M22 x 1.5.
What the standard drill gives you
19.5 mm leaves 77.0% of thread (D - P). That is in the normal 65-80% band most shop charts aim for.
Stainless, tool steel and other tough material
20 mm opens the hole to 61.6% engagement. Less material for the tap to cut means less torque and less heat, at the cost of some thread depth.
Using a form (roll) tap
A form tap displaces metal instead of cutting it, so it needs a larger hole: 21 mm, against a theoretical 20.9 mm. Treat that as a starting point and check your tap maker's chart.
Closest inch size
7/8-9 is the nearest inch thread by diameter (22.23 mm against 22 mm). It is a planning reference only. The two are not interchangeable: the pitches differ, and a bolt from one will not run into a hole tapped for the other.

Related sizes

Same diameter, different pitch

Next size up and down

Closest inch size

7/8-9 49/64″ · 0.7656 in · 19.45 mm · 75.8% 22.23 mm major against 22 mm

Not interchangeable. 7/8-9 is the nearest size by diameter, nothing more. The pitches differ, so a 7/8-9 fastener will not run into a M22 x 2.5 hole and forcing one will strip both.

Guides for tapping M22 x 2.5

Longer reads on the decisions behind the numbers above.

All guides →

M22 x 2.5 tap drill: common questions

What size drill bit do I need for a M22 x 2.5 tap?
A 19.5 mm drill, 0.7677 in. That leaves 77.0% of thread, which is the standard chart figure for M22 x 2.5.
What is the drill size for a M22 x 2.5 tap in inches?
The 19.5 mm tap drill measures 0.7677 in. If you only have inch drills, 49/64 in (0.7656 in) is the closest, giving 78.6% thread.
What drill should I use for M22 x 2.5 in stainless steel?
Use 20 mm instead of 19.5 mm. It leaves 61.6% of thread rather than 77.0%, so there is less material for the tap to cut and less chance of snapping it.
Is M22 x 2.5 the same as M22 x 2?
No. Both are 22 mm threads, but the pitch differs, so the drills differ: 19.5 mm for M22 x 2.5 and 20 mm for M22 x 2. The taps and the fasteners are not interchangeable.
What is the clearance hole for an M22 x 2.5 bolt?
For a medium fit, 24 mm per ISO 273. A clearance hole is not tapped; the bolt passes straight through it.
A 4 × 6 in card with the drills for this size.