When to use this
Use this probability model when the setup matches
Single-card draws, simple spinners, basic classroom probability, and any scenario where you already know the favourable count and the total count.
What this result means
Interpret the probability in three formats
The result tells you how often the event would happen in the long run if each outcome is equally likely. The same probability is shown as an exact fraction, a decimal, and a percent.
Formula: P(E) = favorable outcomes / total outcomes
Inputs
Enter favourable outcomes and total outcomes
This calculator requires each outcome to be equally likely.
Favourable outcomes
How many outcomes count as successful or winning.
What to enter: A whole number from 0 up to the total outcomes.
How to use it: Count only the outcomes that satisfy the success or win.
Example: Drawing an ace from a standard deck gives 4 favourable outcomes.
Total outcomes
The full number of equally likely outcomes in the sample space.
What to enter: A positive whole number.
How to use it: Use the total pool before the event is checked.
Example: A standard deck has 52 possible single-card outcomes.
Worked examples
Quick checks with common probability questions
Draw an ace
A standard deck has 4 aces out of 52 cards.
The probability is 1/13, which is 0.076923 or 7.6923%.
Load this example into the calculatorDraw a heart
A standard deck has 13 hearts out of 52 cards.
The probability is 1/4, which is 0.25 or 25%.
Load this example into the calculator