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Probability Calculator

Compute simple probability as favorable outcomes divided by total outcomes — coin flips, dice rolls, card draws. See 3 in 10 read as 30.0% instantly — free, local, no signup.

100% Local Browser Native

How to Use the Probability Calculator

1. Enter the counts

Favorable outcomes and total possible outcomes (e.g. 1 and 6 for one die face).

2. Read the percentage

Single-event probability with a visual bar.

3. Try presets

Coin Flip, Dice Roll, and Deck of Cards presets demonstrate the setup.

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Frequently Asked Questions

Lottery odds?

Not directly — this tool divides two counts you supply, so 6 and 49 reads 12.2%, which is not the lottery odds (real 6/49 combinatorics give about 1 in 14 million). Enter precomputed counts only; it never computes combinations.

Independent vs conditional?

Neither — the tool computes one simple ratio (favorable ÷ total). Multi-event, with-replacement, and conditional setups must be reduced to two counts by hand first.

Percentages?

Results show as a percentage with one decimal plus a bar (3 in 10 reads 30.0%). No fraction or odds-ratio display — convert those by hand.

Do event odds upload?

No — math runs locally in your browser. Numbers never leave your device.

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Last updated October 2026