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Calculate combinations (n choose r) for probability and odds.
🃏 Combinations: choosing r items from n, order doesn't matter. Lottery odds use this.
A combination counts how many ways to choose r items from n, where order doesn't matter. Choosing 3 toppings from 10 is the same no matter which order you pick them — that's a combination.
C(n,r) = n! / (r! × (n−r)!). For choosing 3 from 10: 10! / (3! × 7!) = 120.
The Combination Calculator lets you figure out combination calculatorinstantly, without reaching for a spreadsheet or doing the math by hand. Whether you're planning a budget, checking a loan, or working through homework, the tool applies the correct formula behind the scenes and shows the result the moment you enter your numbers.
Unlike a static chart or table, this calculator adapts to your exact inputs. You can adjust any value and see the outcome update in real time, which makes it easy to compare scenarios — for example, "what if the rate were 1% lower?" or "what if I paid an extra $50 a month?"
Common uses: people reach for this tool when they need to find a n choose r calculator, combination calculator with steps, lottery odds combinations calculator, or ncr formula calculator.
Browser-based tools like this one have a few real advantages over installed software or manual methods:
The Combination Calculator is based on the following formula:
C(n, k) = n! / [ k! × (n − k)! ]
Variables: C(n, k) = Number of ways to choose k from n, unordered n = Total items available k = Items chosen ! = Factorial: n! = n × (n−1) × … × 1
Number of ways to choose k items from n without regard to order. Read as "n choose k"; central to binomial probability and Pascal's triangle.
Worked example: Step 1: Choose 2 pizza toppings from 5: n = 5, k = 2. Step 2: 5! = 120, 2! = 2, (5 − 2)! = 3! = 6. Step 3: C(5, 2) = 120 / (2 × 6) = 120 / 12 = 10. Result: there are 10 different topping pairs.
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