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Combination Calculator

Calculate combinations (nCr) and permutations (nPr) for counting and probability problems.

Input Values

n = total number of items
r = number of items to select

Formulas

Combination (order doesn't matter)

C(n,r) = n! / (r!(n-r)!)

Permutation (order matters)

P(n,r) = n! / (n-r)!

Combination with Repetition

C(n+r-1, r)

Permutation with Repetition

n^r

Quick Examples

C(5,2) - Choose 2 from 510
C(10,3) - Choose 3 from 10120
C(52,5) - Poker hand2,598,960

Combinations C(10,3)

120

ways to choose 3 from 10

CC(10,3)
120
PP(10,3)
720
n!10!
36,28,800
r!3!
6

All Counting Results

Combination (no repetition)120
Permutation (no repetition)720
Combination (with repetition)220
Permutation (with repetition)1,000

Step-by-Step Calculation

C(10,3) = 10! / (3! x (10-3)!)

= 10! / (3! x 7!)

= 120

Combinations vs Permutations

Combinations

Order does NOT matter. Used when selecting a group.

Example: Choosing 3 people for a committee from 10 people.

Permutations

Order DOES matter. Used when arranging items.

Example: Arranging 3 books on a shelf from 10 books.

What Is a Combination Calculator?

A combination calculator helps you perform combination calculations quickly and accurately. Enter your values and get instant results with step-by-step breakdowns showing exactly how each result was derived.

This calculator handles 2 input values: n, r. Results are computed using standard mathematical formulas and displayed with precision suitable for homework, professional work, and quick references.

The Combination Formula

The calculator applies the following mathematical relationships:

Combination Formula

Computed from input values using standard formulas

Where:

  • Input= Enter values in the input fields to compute results

Understanding the Results

The results display shows the computed value{s} along with related quantities. Each result is computed using JavaScript's built-in Math functions (Math.PI, Math.sqrt, etc.) for maximum precision.

All results are shown to four decimal places by default, which is sufficient for most practical applications including construction, engineering, and academic work.

How to Use This Calculator

  1. Enter n: Type a value in the n field. Default value is 10.
  2. Enter r: Type a value in the r field. Default value is 3.
  3. Read the results: The calculator updates immediately as you type, showing computed values with full step-by-step breakdowns.

Real-World Applications

Combination calculations appear in numerous fields. In education, students use them to verify homework answers and understand the underlying formulas. In engineering, these calculations inform design decisions and safety margins. In everyday life, quick calculations help with home improvement projects, budgeting, and planning.

The specific formulas used by this calculator are standard in the field and can be verified in any mathematics or engineering textbook. Bookmark this page as a quick reference whenever you need to perform combination calculations.

Worked Examples

Example Calculation

Problem:

Use the default values to compute the result.

Solution Steps:

  1. 1Enter n = 10.
  2. 2Enter r = 3.
  3. 3The calculator computes the result using the appropriate formula.
  4. 4Review the step-by-step breakdown to understand the process.

Result:

The computed result is displayed in the highlighted result card above.

Tips & Best Practices

  • ✓Double-check your inputs — a single typo can produce dramatically different results.
  • ✓Use consistent units throughout — don't mix centimeters with inches or meters with feet.
  • ✓Review the step-by-step breakdown to verify that the formula was applied correctly for your inputs.
  • ✓Bookmark this page for quick access to combination calculations whenever needed.
  • ✓For very large or small numbers, the calculator may display results in exponential notation.
  • ✓Compare results with manual calculations occasionally to build confidence in the tool and your math skills.

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Frequently Asked Questions

Calculations use JavaScript's built-in Math functions with double-precision floating-point arithmetic, providing approximately 15 significant digits of accuracy. Displayed values are rounded to four decimal places for readability while maintaining sufficient precision for most applications.
This is a web-based calculator that requires an internet connection to load. Once loaded, all calculations are performed client-side in your browser, so no data is sent to any server.
The calculator is unit-agnostic — enter your values in any consistent unit system (metric or imperial), and results will be in the corresponding units. Mixing unit systems will produce incorrect results.
Yes, this calculator is completely free with no registration required. Use it as many times as you need for homework, professional work, or personal projects.
If you find an issue or have a suggestion for improving this calculator, please reach out through the contact options on the site. We're always looking to make our tools more useful and accurate.

Sources & References

Last updated: 2026-06-06

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Editorial Note

MyCalcBuddy Editorial Team

This page is maintained as an educational calculator reference.

Source

Formula Source: Handbook of Mathematical Functions

by Abramowitz & Stegun

UpdatedLast reviewed: May 2026
CheckedFormula checks are based on standard references and internal QA review.