The Permutation and Combination Calculator helps you distinguish between ordered selections and unordered selections and calculate either result from the values you enter.
What You Need to Know
Before calculating, identify the known values and decide exactly what you want to find. For this tool, the key rule is: Permutations count ordered selections: P(n,r) = n! Γ· (nβr)!. Combinations count unordered selections: C(n,r) = n! Γ· [r!(nβr)!].
Step-by-Step Method
- Choose the correct input type or unit.
- Enter the known quantity or quantities.
- Review the entries before calculating.
- Read the result together with its unit or mathematical notation.
A Quick Example
For a basic check, choose simple values and apply the rule above by hand. Enter the same values into the calculator and compare the two results. This is a useful way to confirm that you understand what each input represents.
Accuracy and Rounding
Numerical precision and real-world accuracy are not the same thing. A calculator can carry out arithmetic precisely, while measured or estimated inputs may have limited precision. When appropriate, keep extra digits during intermediate calculations and round the final answer to a sensible level.
When the Result Looks Wrong
Check the units first, then review decimal points, negative signs, and the values entered in every field. For formula-based calculations, also make sure the conditions required by the formula are satisfied.