CNC Drilling Speeds and Feeds Calculator

How to use this calculator

1. Choose Metric or Imperial units. The operation is fixed: standard rotating drilling.
2. Choose what to calculate: RPM and feed rate (from a cutting speed and feed per revolution you already have), or cutting speed and feed per revolution (from a spindle RPM and feed rate you already have).
3. Enter the drill diameter and the two remaining values for your chosen mode.
4. Optionally open "Estimate feed-only drilling time" to add the hole type, hole depth to full diameter, hole count, drill point angle and any overtravel.
5. Optionally open "Add machine limits" to compare the calculated RPM and feed rate against your machine's maximums.
6. Review the calculation summary, the formula used, and any warnings shown.

What do I need to enter?

• Unit system — Metric (mm, m/min, mm/rev, mm/min) or Imperial (in, SFM, IPR, IPM). Switching converts the figures already entered.
• What do you want to calculate? — RPM and feed rate, from a cutting speed and feed per revolution; or cutting speed and feed per revolution, from a spindle RPM and feed rate.
• Drill diameter — above zero, up to 500 mm.
• Cutting speed and Feed per revolution — entered in the first mode. Above zero, up to 10,000 m/min and 50 mm/rev.
• Spindle RPM and Feed rate — entered in the second mode. Above zero, up to 1,000,000 RPM and 500,000 mm/min.
• Estimate feed-only drilling time (optional) — enter a hole depth to full diameter, up to 10,000 mm, to switch it on. Then set Through or Blind, the number of holes (1 to 100,000), the drill point angle (above 0° and below 180°) and any additional overtravel (zero or more, up to 10,000 mm).
• Maximum spindle RPM and Maximum feed rate (optional) — your machine's limits, to compare against the calculated values. They never change the result.

The limits above are metric; in imperial the same limits apply in converted units.

What do the results show?

• Spindle speed (first mode) or Cutting speed (second mode) — the main figure.
• Feed rate or Feed per revolution — the other calculated value, shown beside the two values you entered.
• Calculation summary — each quantity, its value, and whether it was entered or calculated, with the drill circumference.
• Feed-only drilling time — point approach, feed travel per hole, time per hole and total time for all holes. It appears once you enter a hole depth.
• Machine limits — whether the calculated spindle speed and feed rate sit within or above the limits you entered.
• Formula used — the equations behind the figures, with your numbers in.

How are drilling speeds and feeds calculated?

Spindle speed comes from the cutting speed and drill diameter, and feed rate comes from the feed per revolution and the spindle speed. This calculator always uses the direct formula for the values entered, on full-precision numbers, rather than chaining through a rounded intermediate result.

Worked example, metric: a 10 mm drill at a cutting speed of 100 m/min needs RPM = (100 × 1,000) ÷ (π × 10) ≈ 3,183.1 RPM. At a feed per revolution of 0.15 mm/rev, feed rate = 0.15 × 3,183.1 ≈ 477.5 mm/min.

Worked example, imperial: a 0.5 in drill at 300 SFM needs RPM = (300 × 12) ÷ (π × 0.5) ≈ 2,291.8 RPM. At a feed per revolution of 0.006 IPR, feed rate = 0.006 × 2,291.8 ≈ 13.75 IPM.

In reverse, entering a spindle RPM and feed rate gives the cutting speed and feed per revolution those values imply — useful for checking a program or a machine's actual running parameters against the tool manufacturer's application data.

For the optional feed-only time estimate, an 118° point drilling a 10 mm hole with 2 mm of overtravel has a point approach of (10 ÷ 2) ÷ tan(59°) ≈ 3.0 mm, so a 25 mm deep hole has a total feed travel of 25 + 3.0 + 2 ≈ 30.0 mm before the feed rate is applied. A more acute point angle increases the point approach and the feed-only time; a bare tangent-half-angle formula is used regardless of the actual drill geometry beyond that single angle.

Metric and imperial units used

Every calculation is normalised to millimetres, metres per minute and minutes internally, so switching units converts the figures already entered rather than reinterpreting the same number under a different unit.

What does this calculator assume, and what does it not do?

This calculator covers standard rotating drilling with a single drill, at a fixed diameter, RPM and feed. The feed-only time estimate assumes one continuous feed pass to the entered hole depth, plus the point-approach geometry from the point angle and any overtravel — it does not model peck cycles, retracts, dwell, chip evacuation or any other deep-hole drilling strategy, and "through" versus "blind" hole type changes only the helper copy on the depth field, not the calculation.

It does not calculate torque, thrust, spindle power, tool life, chatter, deflection or hole quality, and it is not an actual CNC cycle time — it excludes rapid approach, retracts, tool changes, machine acceleration and coolant/chip clearing. It does not cover tapping, reaming, boring, counterboring, countersinking, turning or thread milling. For a rotating cutter instead of a drill, see the CNC Milling Speeds & Feeds Calculator, which uses chip load per tooth rather than feed per revolution. This tool does not simulate a machine, generate G-code, or draw on a tool or material database. Any warning it shows is a neutral, calculated callout — never a claim that a result is safe, optimal, suitable, manufacturer-approved or guaranteed. Always check the tool manufacturer's guidance, your machine's actual limits, holder condition and runout, coolant, workholding, hole requirements and your shop's procedures before machining.

Frequently asked questions