PROBABILITY TO OODS/ODDS TO PROBABILITY CALCULATOR
The Probability to Odds Calculator converts probability percentages into odds against—and converts odds against back into probability.
Probability and odds are two different ways of expressing the likelihood that an event will occur. A probability expresses that likelihood as a percentage, while odds against compare the likelihood of the event not occurring to the likelihood that it will occur.
For example, a probability of 25% is equivalent to odds of 3 to 1 against. Conversely, odds of 3 to 1 against represent a 25% probability.
Use either calculator below, depending on the information you already have. Enter a probability to calculate the corresponding odds against, or enter the odds against to convert them back into a probability.
This calculator converts probability and odds only. It does not calculate pot odds.
I think that’s enough for the introduction. Then we go immediately into the actual calculator—no poker strategy, no contextual discussion, and no unnecessary explanation before the user can use the tool.
Probability → Odds Against
Enter a probability percentage to calculate the equivalent odds against.
Odds Against → Probability
Enter the odds against to calculate the equivalent probability percentage.
HOW TO USE THE PROBABILITY TO ODDS CALCULATOR
The Probability to Odds Calculator works in both directions. Use the section that matches the information you already have.
PROBABILITY TO ODDS AGAINST
If you know the probability percentage, enter that number in the Probability (%) field.
For example:
25%
Select Calculate Odds, and the calculator returns:
3 to 1 against
This means an event with a 25% probability is expected not to occur three times for every one time it does occur, over a sufficiently large number of trials.
ODDS AGAINST TO PROBABILITY
If you know the odds against, enter the first number in the Odds Against field.
For example:
3 to 1
Enter 3 in the calculator. The second number remains fixed at 1.
Select Calculate Probability, and the calculator returns:
25%
This means odds of 3 to 1 against correspond to a 25% probability.
Use the Clear button at any time to reset either calculator and enter a new value.
HOW PROBABILITY AND ODDS ARE CALCULATED
Probability and odds against describe the same underlying likelihood in different ways.
CONVERTING PROBBILITY TO ODDS AGAINST
To convert a probability percentage into odds against, use:
Odds Against = (100 − Probability) ÷ Probability
For example, if the probability is 25%:
(100 − 25) ÷ 25 = 3
So:
25% = 3 to 1 against
Another example:
23.53%
(100 − 23.53) ÷ 23.53 = approximately 3.25
So:
23.53% = approximately 3.25 to 1 against
CONVERTING ODDS AGAINST TO PROBABILITY
To convert odds against back into probability, use:
Probability = 1 ÷ (Odds Against + 1) × 100
For example:
3 to 1 against
1 ÷ (3 + 1) × 100 = 25%
So:
3 to 1 against = 25%
Using decimal odds against works the same way:
3.25 to 1 against
1 ÷ (3.25 + 1) × 100 = approximately 23.53%
So:
3.25 to 1 against = approximately 23.53%
PROBABILITY, ODDS AGAINST AND POT ODDS ARE DIFFERENT
This calculator converts probability percentages and odds against.
It does not calculate pot odds.
Odds against describe how likely an event is to occur compared with how likely it is not to occur. Pot odds compare the amount you must call with the size of the pot you can win.
For poker-specific pot and hand-odds calculations, use the Poker Odds Calculator instead.
I would put that distinction right after the formulas. It heads off the most likely source of confusion before we add the internal link.