Method
P(A∪B)=P(A)+P(B)−P(A∩B). Independence gives P(A∩B)=P(A)P(B); mutual exclusivity gives intersection zero.
Math worksheet
Two-Event Probability Calculator
Combine two event probabilities under independence or a supplied intersection, then audit both, either, neither and conditional regions.
The calculation runs locally. Exact-integer tools avoid floating point; decimal and transcendental tools report rounding limits.
Method and verification guide
How the Two-Event Probability Calculator works
P(A∪B)=P(A)+P(B)−P(A∩B). Independence gives P(A∩B)=P(A)P(B); mutual exclusivity gives intersection zero. The calculator keeps the intermediate values visible so you can reproduce the answer independently.
Interpret the result
The partition into A only, B only, both and neither must total probability 1.
Check the assumptions
Independence is an assumption about the process and cannot be inferred from marginal probabilities alone.
Local calculation
Everything runs in this browser. Inputs are not sent to an external calculator.
Rounding
Displayed values may be rounded for readability while calculations use full floating-point precision unless the tool explicitly uses exact integers.
Scope
Independence is an assumption about the process and cannot be inferred from marginal probabilities alone.
Simple by design
Three steps to a clearer number.
Enter your details
Use realistic values in each field. You can change them anytime.
Calculate instantly
The formula runs locally, so there is no account or waiting time.
Use the result
Treat the answer as a practical estimate for your next decision.