# M2.5 tap drill size

The tap drill for an M2.5 × 0.45 metric coarse thread is 2.05 mm (0.0807 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M2.5 × 0.45

| Drill | Inch | Thread % |
|---|---|---|
| 1.95 mm | 0.0768 | 94 % |
| 2.05 mm | 0.0807 | 77 % |
| 2.15 mm | 0.0846 | 60 % |

## M2.5 thread data

- Thread: M2.5 × 0.45 (coarse)
- Pitch: 0.45 mm
- Tap drill: 2.05 mm (0.0807 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 2.7 close, 2.9 normal, 3.1 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 0.45 / 0.45 = 77 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M2.5 × 0.45 tap?**
Use a 2.05 mm drill. It leaves about 77 % thread engagement.

**What is 2.05 mm in inches?**
2.05 mm is 0.0807 inch.

**What size clearance hole for M2.5?**
ISO 273 gives 2.7 mm for a close fit, 2.9 mm normal and 3.1 mm loose.

Source page: https://machinistcharts.com/tap-drill/m2-5/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)