Probability Calculator
Single and combined event probability, odds and complements.
P(A and B) — both
0.15
15% (independent events)
P(A or B) — either
0.65
P(not A)
0.5
P(A) as odds
1 : 1
Neither
0.35
ShowHide the working
- 1Both (independent) = P(A) × P(B) = 0.5 × 0.3 = 0.15
- 2Either = P(A) + P(B) − both = 0.65
Formula
P(A∩B) = P(A)·P(B), P(A∪B) = P(A) + P(B) − P(A∩B)How it works
Combines two independent event probabilities into the chance of both, either, or neither happening.
Example
With P(A) = 0.5 and P(B) = 0.3, both happen 15% of the time and either happens 65%.
Assumes the two events are independent. If one affects the other, these formulas don't apply.
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About the Probability Calculator
Single and combined event probability, odds and complements. It sits in the Statistics section of NWS Calc, a free collection of calculators that run entirely in your browser. There is no signup, no paywall and no tracking — open the page, enter your numbers, get an answer.
Frequently asked questions
- Is the Probability Calculator free to use?
- Yes. Every calculator on NWS Calc is completely free, with no signup, no usage limits and no ads.
- Does my data leave my device?
- No. The Probability Calculator runs entirely in your browser using JavaScript. Nothing you type is uploaded, logged or stored on a server.
- Can I use the Probability Calculator on my phone?
- Yes. The page is fully responsive and works in any modern mobile or desktop browser — there is nothing to install.
- What else is in Statistics?
- Mean, deviation, regression, probability and distributions. You can browse the full Statistics category for related calculators.