How to use the Permutation & Combination Calculator
Enter n and r. Permutations count ordered arrangements; combinations count selections where order does not matter. Enter the known values, choose any required mode or unit, and calculate the result. Review the labels and units before relying on the answer.
What this calculator does
Calculate permutations and combinations for n items taken r at a time. It is intended to make the calculation transparent and repeatable: you provide the known values, the calculator applies the relevant relationship, and the result is shown with the units or labels used by the tool.
When this tool is useful
Use the Permutation & Combination Calculator when you need a quick, repeatable check and already have the inputs requested by the page. It is useful for comparing scenarios, checking hand calculations, planning a task, or understanding how changing one input affects the result.
How the calculation works
Permutations count ordered selections, while combinations count selections where order does not matter.
Practical example
For example, choosing 3 items from 10 gives different counts depending on whether the order of those 3 items matters.
Things to keep in mind
- Check units and input labels before calculating.
- Keep enough decimal precision during the calculation and round the final answer to a level appropriate for your use.
- Use the result as a practical aid and verify it against authoritative requirements when precision has legal, safety, financial, or professional consequences.