# Feeds & speeds calculator

URL: https://www.clove3d.com/tools/feeds-speeds/

Calculate spindle RPM and feed rate for CNC milling and routing from surface speed (Vc), tool diameter and chip load. Supports metric (m/min, mm) and imperial (SFM, in). Includes material presets for carbide tooling.

## Formulas

RPM = (Vc x 1000) / (pi x D)      [metric: Vc in m/min, D in mm]
RPM = (SFM x 12) / (pi x D)       [imperial: D in inches]
feed_rate = RPM x flutes x chipload
feed_per_rev = flutes x chipload
MRR = feed_rate x axial_DOC x radial_WOC

## Inputs

- Units: metric or imperial
- Material preset (sets Vc and chipload automatically) or custom values
- Surface speed (m/min or SFM)
- Tool diameter (mm or in)
- Flutes
- Chip load (mm/tooth or in/tooth)
- Optional: axial depth of cut, radial width of cut, spindle min/max

## Outputs

- Spindle RPM
- Feed rate (mm/min or in/min)
- Feed per revolution
- Material removal rate (when DOC and WOC are set)
- G-code line: S<rpm> F<feed>

## Material starting points (carbide tooling, approximately 6 mm cutter)

| Material        | Surface speed (m/min) | Chip load (mm/tooth) |
|-----------------|-----------------------|----------------------|
| Aluminium       | 250                   | 0.05                 |
| Brass           | 150                   | 0.05                 |
| Mild steel      | 90                    | 0.04                 |
| Stainless steel | 55                    | 0.03                 |
| Hardwood        | 350                   | 0.12                 |
| Softwood / MDF  | 400                   | 0.15                 |
| Acrylic (PMMA)  | 300                   | 0.08                 |

Values are starting points for sharp carbide tooling. Adjust for machine rigidity, tool condition, depth of cut, and coolant.

## FAQ

Q: How do I calculate spindle RPM?
A: RPM = (surface speed x 1000) / (pi x tool diameter) in metric, or (SFM x 12) / (pi x diameter) in imperial. Choose the surface speed for your material and cutter.

Q: What is chip load?
A: Chip load (feed per tooth) is how much material each flute removes per revolution. Feed rate = RPM x flutes x chip load. Too low rubs and dulls the tool; too high overloads it.

Q: Should I change speed or feed first?
A: Set RPM from a conservative surface speed, then raise feed rate until chips look right. Increasing feed helps tool life and finish more than chasing higher RPM.