Probability Calculator
Probability of single events plus union/intersection and complement for two events.
How to Use
- Enter favorable and total outcomes for A and B.
- Toggle independence for intersection formula.
Show Work
Formulas
About the Probability Calculator
Need a hand with everyday maths and number work? The Probability Calculator does the work for you — free, and right here in your browser. Probability of single events plus union/intersection and complement for two events.
How it works
Type your numbers into the boxes. The answer shows up right away — you do not have to press a button. If you change a number, the answer changes too. So you can try different numbers and watch what happens, or check an answer you worked out yourself. Just make sure each box has the right kind of number in it.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
How do I use the Probability Calculator?
Simply type your numbers and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
Try different numbers
Change one thing and watch the answer change. It is an easy way to compare your choices.
Nothing to set up
Open the page and start. There is nothing to install, and no account to make.
Check your work
Worked it out yourself? Use the Probability Calculator to make sure your answer is right.
Safe and private
Everything you type stays on your device. Nothing is sent to a server or saved.
Last updated: