RandomNr

Advanced and Statistical

Random Chance and Odds Simulator

Set a percentage chance and run it once or ten thousand times to see how the odds play out.

Random Odds Simulator

24.9%

25% chance over 1000 trials

The chance

Run it once for a yes or no, or many times to see the rate

Test any probability

This tool simulates a chance you set. Enter a percentage, choose how many trials to run, and see how the odds play out. Run a single trial for a straight yes or no, or thousands of trials to watch the observed rate settle toward the chance you set.

The law of large numbers

A 25 percent chance does not mean one hit in every four tries. Over a handful of trials the result can swing widely, which is why a run of bad luck feels unfair. As the trials mount, the observed rate closes in on the true chance, a pattern known as the law of large numbers, and this tool lets you see it happen.

Fair trials and export

Each trial is an independent draw from the browser cryptographic random source, so no trial leans on the last. The result shows the hits, the total and the observed rate, which you can copy or export for a record.

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Frequently asked questions

What does the odds simulator do

It runs a chance you set, either once for a single yes or no, or many times to show how often it comes up as a percentage.

Why does the observed rate differ from the chance

Randomness varies. Over few trials the observed rate can sit well away from the set chance, and it settles closer as the number of trials grows.

What can I model

Anything with a fixed percentage chance: a drop rate, a coin weighted to a percentage, a success roll, or a marketing conversion.

How many trials can I run

Up to one million, which gives an observed rate very close to the true chance.

Is it free

Yes, free and with no sign up.

Related generators

To weight several outcomes rather than one chance, use the weighted generator, or flip a fair coin with flip a coin.