Unique groups, no repeats
Combination Calculator
Count distinct groups when order does not matter and you cannot reuse the same item.
Open calculatorCalculators
Interactive counting and probability calculators
Each calculator answers one type of question with helpful supporting tools. Use the counting pages for arrangement and selection questions, and use the probability pages for chances, repeated trials, and without-replacement draws.
Groups where reuse is allowed
Combination With Repetition Calculator
Count distinct groups when order does not matter but the same item can be chosen more than once.
Open calculatorOrdered selections, no repeats
Permutation Calculator
Count ordered arrangements when position matters and each item can be used once.
Open calculatorOrdered selections with reuse
Permutation With Repetition Calculator
Count ordered outcomes when each position matters and items can repeat.
Open calculatorOrdered lock codes with repeats
Four Dial Lock Combination Calculator
Count possible codes for a four-dial lock when each dial can reuse any allowed symbol.
Open calculatorThree position ordered lock with repeats
Three Number Lock Combination Calculator
Count possible codes for a three-number lock like a combination lock with a rotary dial that can repeat any of the values on each spin.
Open calculatorOrder matters, duplicates collapse
Multiset Permutation Calculator
Count unique orderings when some items are identical copies, so swapping matching copies does not create a new arrangement.
Open calculatorDescending product
Factorial Calculator
Compute n! and see it written as a descending product of whole numbers.
Open calculatorArrangements around a circle
Circular Permutation Calculator
Count distinct circular arrangements by fixing one position and arranging the rest.
Open calculatorNotation-focused nCr page
Binomial Coefficient Calculator
Compute C(n, r) or nCr directly when the user intent is notation-based instead of phrase-based.
Open calculatorFavourable outcomes over total outcomes
Probability Calculator
Compute simple probability from favourable outcomes and total equally likely outcomes, then see the result as percent, fraction, and decimal.
Open calculatorRepeated trials with the same success chance
Binomial Probability Calculator
Find the probability of exactly, at least, or at most a target number of successes across repeated independent trials with the same success probability.
Open calculatorWithout-replacement draw probability
Hypergeometric Probability Calculator
Find the probability of exactly, at least, or at most a target number of successes when drawing without replacement from a finite pool.
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