Free specialty workspace
Machinist calculator
Use this machinist calculator to convert supplied cutting speed to RPM and calculate milling or drilling feed rates and travel time.
Method version1.0.0 · Reviewed November1,2026 · Calculated on your device
Your calculation
Choose a method, then enter your figures. Examples are illustrative, not recommended settings or rates.
How this calculation works
RPM=cuttingSpeed×unitFactor/(π×effectiveDiameter); milling feed=feedPerTooth×teeth×RPM; travel time=length×passes/feed.
What information do I need?
Only fields for your selected method are required. Use consistent units and scope. Changing an entry method or unit system does not convert the numbers already entered. Previously calculated results are cleared when inputs change.
Input definitions and where to find them
- Measurement system
- Changing units changes how entries are interpreted; existing numbers are not converted. Review every dimension.
- Machining operation
- Select the feed convention in your tooling data.
- Known speed input
- Supply a manufacturer/setup value; the calculator does not select a cutting speed.
- Effective cutting diameter (in US; mm metric)
- Use the effective diameter at the engagement, not a mismatched tool label.
- Known surface speed (ft/min US; m/min metric) OR RPM
- Interpret this value using the selected known-speed input.
- Effective cutting teeth
- Number of effective teeth in the manufacturer feed formula.
- Feed per tooth (milling) or revolution (drilling)
- Inches in US mode, millimeters in metric mode. Supply the appropriate tooling value.
- Feed travel per pass including approach
- Inches in US mode, millimeters in metric mode. Excludes rapid moves and retracts.
- Number of identical feed passes
- Use a positive whole number.
Worked example
This example uses the initial method shown in the selector. Load an example in the form to try it.
Example inputs
- Measurement system: us
- Machining operation: milling
- Known speed input: surface
- Effective cutting diameter (in US; mm metric): 0.5
- Known surface speed (ft/min US; m/min metric) OR RPM: 100
- Effective cutting teeth: 4
- Feed per tooth (milling) or revolution (drilling): 0.002
- Feed travel per pass including approach: 10
- Number of identical feed passes: 1
Example answer: Spindle speed = 763.943727 RPM
Use the result well
Supply speed and chip-load/feed values from the specific tooling manufacturer and setup. These formulas do not select safe or suitable machining parameters. Milling uses effective teeth in cut and feed per tooth; drilling uses feed per revolution. Time excludes tool changes, dwell, retracts, rapid moves, acceleration and other cycle time. Verify effective cutting diameter and all machine/tool limits.
Review the limits shown with each result. Browser arithmetic has finite precision; small differences may reflect rounding. Print or download important results before closing the tab. This workspace does not store projects online or replace an approved examination calculator, engineering design or professional judgment.
Method and sources
References support the stated mathematical concepts; the interface and implementation are original. Publishers do not endorse this site.