Mathlean · Online math workspace
Set cardinality calculator
Count the distinct elements of a supported finite set.
How to use this calculator
Edit Count({1,2,3}). A set discards duplicates before counting.
Tap the math below to edit it and see the result. Once a result is ready, press Tab on a hardware keyboard to accept it. Outside a matrix, Return completes the line; the phone math keyboard has the same Return action.
Try it here
Interactive tools require JavaScript. You can read the guide and example without it.
What to know
Infinite and undecidable set sizes need not have a finite numerical answer.
Mathlean combines visual mathematical input with computation and canvas tools. Results depend on the expression and available engine support; check important answers independently.