Free calculators
Run the numbers before you bet.
Four free tools that run in your browser on prices you enter. No account, no feed, no promise of profit.
The free maths shelf
Four tools, each answering one question. Open one, type your own prices, keep the result.
01 · fair odds
De-vig / fair odds
Strip the bookmaker margin out of two or three way decimal prices and read the de-vigged fair odds and overround.
Worked example
- Home price
- 1.91
- Away price
- 1.91
- Overround
- 4.4%
- Fair odds each side
- 2.00
Example figures, not live prices.
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02 · value
Expected value
Compare your probability estimate against a price and see whether the bet has an edge or a negative expectation.
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03 · staking
Kelly stake
Size a single bet against your bankroll with full or fractional Kelly, and see why the fraction exists.
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04 · windows
Arbitrage stake split
Split a stake across outcomes for an equal return, and check whether the prices are an arbitrage at all before costs.
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Free tools, honest limits
PhotonOdds is a sports-betting data & analytics service — not a bookmaker. We never accept wagers or guarantee profit.
These calculators run on the prices you type in. They check the maths, not the outcome. 18+ only. Betting carries risk. Please gamble responsibly. Read the safer gambling note.