How it works
Fill in the 3 fields above and Probability of A or B Calculator calculates the result instantly, recalculating as you change any value. It applies the formula P(A∪B) = P(A) + P(B) − P(A∩B). The math runs locally in your browser — nothing is sent to a server.
Formula
P(A∪B) = P(A) + P(B) − P(A∩B)Examples
- P(A) 40 %, P(B) 30 %, P(A and B) 10 % → P(A or B): 60%
Frequently asked questions
How do I use the Probability of A or B Calculator?
Enter your values in the 3 input fields and the result is calculated automatically as you type. Change any value to see the numbers update instantly.
What formula does the Probability of A or B Calculator use?
It uses P(A∪B) = P(A) + P(B) − P(A∩B). The calculation is performed in your browser using standard, well-established math for accurate results.
Is my data private?
Yes. The Probability of A or B Calculator runs entirely in your browser. Nothing you enter is uploaded, saved to a server, or shared — it never leaves your device.
Is the Probability of A or B Calculator free?
Yes, it is completely free with no sign-up, no limits and no watermarks. Like every tool on statistics and the rest of the platform, you can use it as often as you like.
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