What is the difference between probability and odds?

Probability compares favorable to total outcomes (1/6 = 16.7%). Odds compare favorable to unfavorable outcomes (1:5). A 1-in-6 chance has probability 16.7% but odds of 1 to 5. Casinos use odds; statisticians use probability.

How do I calculate the probability of at least one success?

It is easier to calculate the complement — the probability of zero successes — and subtract from 1. For a 16.7% single-event probability across 5 trials: 1 − (0.833)⁵ = 1 − 0.402 = 59.8% chance of at least one success.

What is expected value and how is it used?

Expected value multiplies each outcome's probability by its payoff and sums the results. If a lottery ticket has a 1-in-1000 chance of winning $500, the expected value is $0.50 — meaning the ticket is worth more than $0.50 only as entertainment, not as an investment.

Are coin flips really 50/50?

Not exactly. A Stanford study found that coins tend to land on the same face they started on about 51% of the time due to the physics of the flip. For practical purposes, 50/50 is a good approximation, but it is not mathematically exact.

Are the calculations on Probability Calculator | Chance & Expected Value Tools private?

Yes, completely. All calculations are performed entirely locally inside your browser using JavaScript. No inputs or personal metrics are ever transmitted to or stored on our servers.

Probability Calculator | Chance & Expected Value

Probability Calculator – Odds & OutcomesMetriova provides free online calculators for finance, business, health, and construction. Calculate loans, investments, fitness metrics, and project materials in seconds.Probability Basics: Common Event ProbabilitiesProbability ranges from 0 (impossible) to 1 (certain), expressed as P(event) = favorable outcomes / total outcomes. For independent events, multiply probabilities: P(A and B) = P(A) × P(B). For mutually exclusive events, add them: P(A or B) = P(A) + P(B). Expected value = sum of (outcome × probability).

Event

Probability

Odds

Coin flip (heads)

50%

1 in 2

Six-sided die (any number)

16.67%

1 in 6

Drawing an ace from a deck

7.69%

1 in 13

Drawing a heart

25%

1 in 4

Two heads in a row

25%

1 in 4

Rolling a 7 with two dice

16.67%

1 in 6