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Combination Calculator

Select the central point, enter the numbers, and the calculator will determine their absolute deviation around the chosen central point, with step-by-step calculations.

(n)
(r)
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An online number combination calculator allows you to find the number of possible combinations from a dataset. This calculator also lists every possible combination. A combination counts the ways to select r elements from n objects where replacements are not allowed.

Read the full article to learn the combination formula, step-by-step calculations, and how to use a combinations calculator. You can also try our online permutation calculator for ordered subsets with or without repeated items.

Combination Formula

The formula to calculate combinations is:

$$ C(n,r) = \frac{n!}{r!(n-r)!} $$

Where:

  • n = total number of items
  • r = number of items selected
  • nCr = total possible combinations

For combinations with repetition:

$$ C(n,r) = \frac{(r+n-1)!}{r!(n-1)!} $$

Use our factorial calculator for quick factorial calculations.

Step-by-Step Examples

Example 1:

Select 4 students from 30 for athletics.

Solution:

$$ C(30,4) = \frac{30!}{4! \cdot 26!} = \frac{30 \cdot 29 \cdot 28 \cdot 27}{4 \cdot 3 \cdot 2 \cdot 1} = 27,405 \text{ teams} $$

Example 2:

Pick 6 desserts from 24 options.

Solution:

$$ C(24,6) = \frac{24 \cdot 23 \cdot 22 \cdot 21 \cdot 20 \cdot 19}{6 \cdot 5 \cdot 4 \cdot 3 \cdot 2 \cdot 1} = 134,596 \text{ combinations} $$

Example 3:

Give 3 tin cans to 8 people.

Solution:

$$ C(8,3) = \frac{8 \cdot 7 \cdot 6}{3 \cdot 2 \cdot 1} = 56 \text{ ways} $$

Combinations vs Permutations

When order doesn't matter (e.g., lunch: Burger, Reuben sandwich, Apple pie), it is a combination. When order matters (e.g., safe code 5-8-4), it is a permutation. A permutation is an ordered combination.

How to Use the Online Combination Calculator

Inputs:

  • Select dataset elements
  • Enter total number of elements
  • Enter how many to choose
  • Select combination type: standard or with repetition
  • Click calculate

Outputs:

  • Total combinations
  • Total combinations with repetition
  • Step-by-step calculations

FAQs

What does 10 choose 3 mean?

Selecting 3 elements from 10 without order or repetition, giving 120 possible combinations.

What is a combination used for?

Combinations determine all possible selections where order doesn't matter, unlike permutations where order matters.

Quick nCr Reference Table

n-CHOOSE-k nCk
2 choose 1 2
2 choose 2 1
3 choose 1 3
3 choose 2 3
3 choose 3 1
4 choose 1 4
4 choose 2 6
4 choose 3 4
4 choose 4 1
5 choose 1 5
5 choose 2 10
5 choose 3 10
5 choose 4 5
5 choose 5 1
6 choose 1 6
6 choose 2 15
6 choose 3 20
6 choose 4 15
6 choose 5 6
6 choose 6 1

References:

Wikipedia: Combination definition & formulas
Britannica: Difference between Combination & Permutation
Math StackExchange: Find all combinations of a set

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