Probability Calculator
Enter your values below and click Calculate for instant results.
Calculate single event probability, combined events (AND/OR), conditional probability, and complements.
Enter your values below and click Calculate for instant results.
Probability measures how likely an event is to occur, expressed as a number between 0 (impossible) and 1 (certain). A probability of 0.5 means the event is equally likely to happen or not happen. Probabilities can also be expressed as percentages (50%) or odds (1 to 1).
When a probability is given as a fraction (like 3/10), convert it to a decimal by dividing: 3 divided by 10 equals 0.30. Enter this decimal value into the calculator. The result will be shown as both a decimal and a percentage.
Two events are independent when the outcome of one does not affect the probability of the other. Flipping a coin twice produces two independent events. Two events are dependent when one affects the other, like drawing two cards from a deck without replacement. The "AND" calculation in this calculator assumes independence. For dependent events, a different approach using conditional probability is needed.
The probability that an event does not occur equals 1 minus the probability that it does. This is useful when it is easier to calculate the probability of an event happening than not happening. For example, the probability of rolling at least one six on two dice is easier to calculate as 1 minus the probability of rolling no sixes on either die.