Odds Converter Guide
Convert between decimal (Betfair), fractional (UK bookmakers), American (US), and implied probability.
Formats
- Decimal — total return per £1 staked (e.g. 2.50).
- Implied % — market probability from odds.
- Fractional — profit vs stake (e.g. 6/4).
- American — +150 or -200 moneyline format.
Implied % = (1 ÷ decimal odds) × 100
Enter any one format — others update on Calculate or when you leave the field.
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Fractional values are simplified approximations.
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Betfair back/lay mechanics. Commission field on each tool — set to 0% to exclude fees.
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When to use this calculator
Use when comparing prices across bookmakers (fractional), exchanges (decimal), or US sites (American +150 / -200). Also converts to implied probability — useful for EV calculations and spotting value.
Frequently asked questions
What odds format does Betfair use?
Betfair displays decimal odds by default. Decimal 2.0 means even money (double your stake back including the stake).
How do I convert decimal to implied probability?
Implied probability (%) = (1 ÷ decimal odds) × 100. For example, odds of 4.0 imply a 25% chance.
What is the difference between decimal and fractional odds?
Decimal odds include your stake in the return. Fractional odds (e.g. 3/1) show profit only relative to stake.
How do American odds work?
Positive American odds (e.g. +150) show profit on a $100 stake. Negative odds (e.g. -200) show how much you must stake to win $100. The converter handles both.
Disclaimer: For educational and planning purposes only. Not financial or betting advice. 18+ · BeGambleAware.org