Metric drill · 25 mm
25 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes
https://shopmath.org/drills/metric/25mm · data verified August 1, 2026
A 25 mm drill bit is 0.9843 in (25.000 mm) in diameter. It is the tap drill for M27×2 at 75% thread engagement with a cut tap, where it leaves 77.0% thread. The nearest fractional size is 63/64" at 0.9844 in. Diameters are nominal.
- Series
- Metric
- Designation
- 25 mm
- Inch
- 0.9843
- mm
- 25.000
- Standard
- ANSI/ASME B94.11M
Metric Drill · 25 mm · nominal diameter
0.9843 in
- Millimetre
- 25.000mm
- Taps
- M27×2
Nominal diameter. As a tap drill it leaves 77.0% thread in M27×2 with a cut tap.
25 mm Drill Bit Size in Inches and Millimetres
The nominal diameter of a 25 mm drill bit. Drill sizes are nominal — a worn drill, run-out or a soft material that closes in behind the cut all move the finished hole.
| Property | Value |
|---|---|
| Diameter, decimal inch | 0.9843 in |
| Diameter, millimetre | 25.000 mm |
| Cross-sectional area | 0.76086 in² |
1 in = 25.4 mm exactly, so the two columns are the same value in different units, not two measurements.
Threads a 25 mm Drill Bit Taps
Every thread in this reference whose tap drill is the 25 mm drill bit, and the thread engagement it leaves. The engagement asked for and the engagement the drill actually produces are different numbers — that gap is why both columns are here.
| Thread | Series | Thread % asked for | Thread % this drill leaves |
|---|---|---|---|
| M27×2 | ISO Metric Fine | 75%default | 77.0 |
| M30×2 | ISO Metric Fine | 75%default | 192.4 |
| M30×3.5 | ISO Metric Coarse | 75%default | 110.0 |
| M33×2 | ISO Metric Fine | 75%default | 307.9 |
| M33×3.5 | ISO Metric Coarse | 75%default | 176.0 |
| M36×3 | ISO Metric Fine | 75%default | 282.3 |
| M36×4 | ISO Metric Coarse | 75%default | 211.7 |
| M39×3 | ISO Metric Fine | 75%default | 359.2 |
| M39×4 | ISO Metric Coarse | 75%default | 269.4 |
| M42×3 | ISO Metric Fine | 75%default | 436.2 |
| M42×4.5 | ISO Metric Coarse | 75%default | 290.8 |
| M45×3 | ISO Metric Fine | 75%default | 513.2 |
| M45×4.5 | ISO Metric Coarse | 75%default | 342.1 |
| M48×3 | ISO Metric Fine | 75%default | 590.2 |
| M48×5 | ISO Metric Coarse | 75%default | 354.1 |
| M52×4 | ISO Metric Fine | 75%default | 519.6 |
| M52×5 | ISO Metric Coarse | 75%default | 415.7 |
| M56×4 | ISO Metric Fine | 75%default | 596.6 |
| M56×5.5 | ISO Metric Coarse | 75%default | 433.9 |
| M60×4 | ISO Metric Fine | 75%default | 673.6 |
| M60×5.5 | ISO Metric Coarse | 75%default | 489.9 |
| M64×4 | ISO Metric Fine | 75%default | 750.6 |
| M64×6 | ISO Metric Coarse | 75%default | 500.4 |
| M27×2 | ISO Metric Fine | 50% | 77.0 |
Values are for cut taps. 161 thread/engagement combinations use this drill; the first 24 are shown. Rows marked default are the shop-default engagement for that thread.
Fasteners That Pass Through a 25 mm Drill Bit Hole
A hole drilled with a 25 mm drill bit is the standard clearance hole for these fasteners — the through-hole the bolt passes freely, not the tapped hole.
| Fastener | Series | Clearance class |
|---|---|---|
| M22×1.5 | ISO Metric Fine | loose |
| M22×2 | ISO Metric Fine | loose |
| M22×2.5 | ISO Metric Coarse | loose |
| M24×2 | ISO Metric Fine | normal |
| M24×3 | ISO Metric Coarse | normal |
| M27×2 | ISO Metric Fine | close |
| M27×3 | ISO Metric Coarse | close |
| M30×2 | ISO Metric Fine | close |
| M30×3.5 | ISO Metric Coarse | close |
| M33×2 | ISO Metric Fine | close |
| M33×3.5 | ISO Metric Coarse | close |
| M36×3 | ISO Metric Fine | close |
| M36×4 | ISO Metric Coarse | close |
| M39×3 | ISO Metric Fine | close |
| M39×4 | ISO Metric Coarse | close |
| M42×3 | ISO Metric Fine | close |
| M42×4.5 | ISO Metric Coarse | close |
| M45×3 | ISO Metric Fine | close |
| M45×4.5 | ISO Metric Coarse | close |
| M48×3 | ISO Metric Fine | close |
| M48×5 | ISO Metric Coarse | close |
| M52×4 | ISO Metric Fine | close |
| M52×5 | ISO Metric Coarse | close |
| M56×4 | ISO Metric Fine | close |
| M56×5.5 | ISO Metric Coarse | close |
| M60×4 | ISO Metric Fine | close |
| M60×5.5 | ISO Metric Coarse | close |
| M64×4 | ISO Metric Fine | close |
| M64×6 | ISO Metric Coarse | close |
Clearance classes per ISO 273 (metric) and ASME B18.2.8 (inch): close for located joints, normal for general assembly, loose for slotted or adjustable joints.
25 mm Drill Bit Equivalents in Every Other Drill Series
The closest size to the 25 mm drill bit in each of the other three indexes, with the difference in inches. None of them is the same drill — check the difference before substituting one into a tapped hole.
| Property | Property | Diameter | Property | |
|---|---|---|---|---|
| Drill | Series | in | mm | Difference, in |
| #1 | Number | 0.2280 | 5.791 | −0.7563 |
| Z | Letter | 0.4130 | 10.490 | −0.5713 |
| 63/64" | Fractional | 0.9844 | 25.003 | +0.0001 |
A positive difference means the equivalent drill is larger, which leaves less thread in a tapped hole. Sizes without a link are stored for the nearest-drill calculation but do not carry their own page.
Drill Sizes Either Side of the 25 mm Drill Bit
Ordered by diameter across all four indexes, so the next size up may be a letter, a fraction or a metric drill rather than the next one in this series.
Sources and Method for the 25 mm Drill Bit Size
- Drill diametercomputed
Number/letter: bd_warehouse drill_sizes.csv (Apache-2.0) cross-checked against Wikipedia Drill bit sizes (CC BY-SA 4.0). Fractional: computed 1/64 in steps per ANSI B94.11M. Metric: computed BS 328 increment pattern.
Verified against Wikipedia Drill bit sizes (CC BY-SA 4.0); 31/31 checks passed
Computed from the standard's formulas, then checked against published tables.
- Tap drill usagecomputed+compiled
bd_warehouse drill_sizes.csv (Apache-2.0) + Wikipedia Drill bit sizes (CC BY-SA 4.0); fractional and metric computed from ANSI B94.11M / BS 328 increment patterns
Verified against drills: 31 checks passed across 1 harness(es)
Part computed from the standard's formulas, part compiled from agreeing public sources.
- Assumptions
- Diameters are nominal. Drill manufacturing tolerance, wear and run-out all cut oversize, and every one of those moves a tapped hole toward less thread than the table says.
- Tap drill usage assumes cut taps. M27×2 at 75% requested engagement is what this drill is normally bought for.
- Dataset scope: Number sizes #61-#80 are stored but tagged demandTier 'extended' — query-space-map.md Appendix A found the tail thinning in the 60s. Sizes below #80 and metric sizes above 25.0 mm excluded.
- Data last verified
- August 1, 2026
How to Cite This 25 mm Drill Bit Reference
Citation
ShopMath. "25 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes." ShopMath, verified August 1, 2026, https://shopmath.org/drills/metric/25mm
BibTeX
@misc{shopmath-drills-metric-25mm,
title = {25 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes},
author = {{ShopMath}},
year = {2026},
howpublished = {\url{https://shopmath.org/drills/metric/25mm}},
note = {Data verified 2026-08-01}
}Permanent URL
https://shopmath.org/drills/metric/25mm
Common Questions About the 25 mm Drill Bit
What size is a 25 mm drill bit?
- A 25 mm drill bit is 0.9843 in in diameter, which is 25.000 mm.
What thread does a 25 mm drill bit tap?
- A 25 mm drill bit is the tap drill for M27×2 at 75% requested thread engagement, where it leaves 77.0% thread with a cut tap. It is the default tap drill for 23 threads in this reference.
What fraction is a 25 mm drill bit closest to?
- A 25 mm drill bit (0.9843 in) sits closest to the 63/64" fractional drill at 0.9844 in, a difference of 0.0001 in.
What bolt fits through a 25 mm drill bit hole?
- A hole drilled with a 25 mm drill bit is the standard loose clearance hole for M22×1.5, and a clearance hole for 28 other fastener sizes listed on this page.
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