Probability Calculator
Probability Calculator
Enter how many outcomes count as "favorable" (the event you care about) and how many total possible outcomes there are. This calculates the probability as a decimal, a percentage, the odds in favor, and a plain-language sense of how likely that actually is.
This is the foundational probability formula that every more specialized calculator on this site — binomial, Poisson, conditional, and the rest — ultimately builds on: probability equals favorable outcomes divided by total outcomes, always landing somewhere between 0 (impossible) and 1 (certain). It assumes every outcome is equally likely, which holds for scenarios like drawing a card from a well-shuffled deck or rolling a fair die, but wouldn't apply directly to situations with biased or weighted outcomes.
- Formula: Probability = Favorable Outcomes ÷ Total Outcomes — always a value between 0 (impossible) and 1 (certain).
- Odds vs. probability: "3:7 odds" means 3 favorable outcomes for every 7 unfavorable ones — a related but distinct way of expressing the same likelihood.
- Equally likely outcomes assumed: this basic formula assumes every possible outcome is equally likely (like a fair coin or die) — for events with unequal likelihoods, you'd need a weighted approach instead.
What's the difference between probability and odds?
Probability compares favorable outcomes to ALL outcomes (3 out of 10 total), while odds compare favorable to unfavorable outcomes only (3 to 7) — they describe the same event but aren't numerically the same.
Can probability be greater than 1 or less than 0?
No — a valid probability is always between 0 (the event never happens) and 1 (the event always happens); this calculator caps results within that range.
Probability Calculator
Enter how many outcomes count as "favorable" (the event you care about) and how many total possible outcomes there are. This calculates the probability as a decimal, a percentage, the odds in favor, and a plain-language sense of how likely that actually is.
This is the foundational probability formula that every more specialized calculator on this site — binomial, Poisson, conditional, and the rest — ultimately builds on: probability equals favorable outcomes divided by total outcomes, always landing somewhere between 0 (impossible) and 1 (certain). It assumes every outcome is equally likely, which holds for scenarios like drawing a card from a well-shuffled deck or rolling a fair die, but wouldn't apply directly to situations with biased or weighted outcomes.
- Formula: Probability = Favorable Outcomes ÷ Total Outcomes — always a value between 0 (impossible) and 1 (certain).
- Odds vs. probability: "3:7 odds" means 3 favorable outcomes for every 7 unfavorable ones — a related but distinct way of expressing the same likelihood.
- Equally likely outcomes assumed: this basic formula assumes every possible outcome is equally likely (like a fair coin or die) — for events with unequal likelihoods, you'd need a weighted approach instead.
What's the difference between probability and odds?
Probability compares favorable outcomes to ALL outcomes (3 out of 10 total), while odds compare favorable to unfavorable outcomes only (3 to 7) — they describe the same event but aren't numerically the same.
Can probability be greater than 1 or less than 0?
No — a valid probability is always between 0 (the event never happens) and 1 (the event always happens); this calculator caps results within that range.