Probability Calculator
Calculate probability of independent events.
Assumes A and B are independent events (one doesn't affect the other).
About this tool
For two independent events — where the outcome of one doesn't affect the other — this calculates the probability that both happen, that at least one happens, and that neither happens, from each event's individual probability.
Key Features
- P(A and B) for independent events
- P(A or B) via inclusion-exclusion
- P(neither)
How to Use
- Enter the probability of event A as a percentage.
- Enter the probability of event B as a percentage.
- Click Calculate Probability.
Benefits
- Understand combined probability without manual multiplication
- Check odds calculations for games, dice, or independent risks
- See all three related probabilities at once
Frequently Asked Questions
It means knowing whether A happened tells you nothing about whether B happens — like two separate coin flips. If your events are dependent (like drawing cards without replacement), this simple multiplication rule doesn't apply.
Using inclusion-exclusion: P(A) + P(B) − P(A and B). Subtracting P(A and B) avoids double-counting the overlap where both events happen.