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Drilling Speeds and Feeds

Guide · Updated October 27, 2026

Drilling uses the same two numbers as milling: surface speed sets the RPM, and feed per revolution sets how hard the drill cuts. Get both close and the drill cuts cleanly and lasts. Here are the formulas, conservative starting values and worked examples.

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The free speeds and feeds calculator turns SFM or m/min into RPM. For precision setups, the Gage Block Calculator builds any stack. Free, no login.

Formulas

Inch: RPM = SFM × 3.82 ÷ D, and IPM = RPM × in/rev
Metric: RPM = 1000 × Vc ÷ (π × D), and mm/min = RPM × mm/rev

Conservative starting speeds (HSS drills)

Material	SFM	m/min
Aluminum	200–300	60–90
Brass	150–200	45–60
Mild steel	80–100	25–30
Stainless (300 series)	30–50	10–15

Starting points only. Coated and carbide drills run faster; follow the drill maker's data.

Worked examples

1/2 in HSS, mild steel, 90 SFM: 90 × 3.82 ÷ 0.5 ≈ 688 RPM. At 0.006 in/rev, that's about 4.1 IPM.
10 mm HSS, mild steel, 25 m/min: 1000 × 25 ÷ (π × 10) ≈ 796 RPM. At 0.15 mm/rev, that's about 119 mm/min.
1/4 in HSS, aluminum, 250 SFM: 250 × 3.82 ÷ 0.25 = 3,820 RPM. At 0.005 in/rev, that's about 19 IPM.

Step by step

Pick a surface speed: Choose a conservative SFM or m/min for the drill and material.
Work out RPM: RPM = SFM × 3.82 ÷ D (in), or 1000 × Vc ÷ (π × D) (mm).
Pick a feed per rev: Start in the middle of the range for the drill size.
Work out feed rate: IPM = RPM × in/rev, or mm/min = RPM × mm/rev.
Peck and adjust: Peck deep holes to clear chips, then adjust from chip shape and sound.

Tips

Spot or center drill first so the drill doesn't walk.
Peck at about 1 to 1.5 diameters deep in steel, and clear chips often in deep holes.
Large drills on light machines may need less RPM than the formula gives.
For milling, see feeds and speeds basics.

FAQ

How do I calculate drill RPM?

RPM = SFM × 3.82 ÷ drill diameter in inches, or RPM = 1000 × Vc ÷ (π × D) in metric with Vc in m/min and D in mm. A 1/2 in HSS drill in mild steel at 90 SFM runs about 690 RPM.

What feed should I use for drilling?

Feed per revolution scales with drill size. As a rough starting point for HSS in steel: about 0.002 to 0.004 in/rev for 1/8 in, 0.004 to 0.007 for 1/4 in, and 0.007 to 0.012 for 1/2 in. Check the drill maker's data.

How do I convert feed per rev to IPM?

IPM = RPM × feed per rev. At 690 RPM and 0.006 in/rev that's about 4.1 IPM.

Why do drills squeal or burn?

Usually too much speed, too little feed, or a dull drill. Slow the spindle, feed firmly so the drill cuts rather than rubs, and use coolant.

Is there a free speeds and feeds calculator?

Yes. The AskMachinist speeds and feeds calculator converts surface speed to RPM in inch and metric. It's free, with no login.

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General shop information only — follow your gage manufacturer's instructions and your quality system.