What if r > n?
Permutations and combinations are undefined when r exceeds n, so the calculator prompts you to adjust the inputs.
Step-by-step walkthrough
Permutation Combination Calculator Guide
Use this companion guide beside the interactive calculator to make sure you understand the “why” behind every click. Each section includes the classroom explanation, student-friendly language, and quick practice prompts.
Before you start
Collect the data points listed below and double-check their units. Keeping an organized “givens” list is one of the fastest ways to reduce math errors and impress exam graders.
- permutation
- combination
- factorial
Detailed procedure
Step 1
Enter n (the total items) and r (items selected or arranged).
Step 2
Review n!, nPr, and nCr instantly—values are exact integers.
Step 3
Use the formatted result in proofs, probability setups, or combinatorics homework.
Teaching & troubleshooting tips
How large can n be?
Values up to n = 300 are supported. Beyond that, factorials exceed the safe range for display and may be unwieldy.