Four free tools covering every calculation you need — odds conversion, parlay returns, bookmaker margin, and optimal stake sizing. No sign-up required.
Convert any odds between decimal, fractional, American, Hong Kong, Malay, Indonesian, and implied probability. Enter once — see all seven outputs instantly.
Add each leg of your accumulator, pick odds format, and see the combined odds, implied win probability, projected profit, and margin compounding warning for 3+ legs.
Paste in the odds for 2, 3, or 4 outcomes. Get the total overround, margin percentage, a quality rating (green/amber/red), and the no-vig fair price for each outcome.
Enter the decimal odds, your estimated win probability, and bankroll. Get full, half, and quarter Kelly stake recommendations with expected value per £100 and a negative EV warning.
Enter your decimal odds and estimated win probability to find whether a bet is +EV or -EV. Shows EV per unit, edge percentage, and break-even probability.
Remove the bookmaker margin from a 2-way or 3-way market to find the true implied probability and fair odds for each outcome. Ideal for line comparison.
Distribute a total stake optimally across 2–6 outcomes to guarantee equal profit on whichever wins. Detects true arbitrage opportunities automatically.
1. Margin Calculator — strip out the vig and get fair prices.
2. Odds Converter — translate to your preferred format if needed.
3. Kelly Calculator — size the bet once you've confirmed positive EV.
For background on the theory behind these tools, see our guides on bookmaker margin, value betting, and the Kelly Criterion.
Yes — all four calculators are completely free to use with no account or sign-up required. They run entirely in your browser.
Decimal, fractional (e.g. 5/2), American (+150 or -200), Hong Kong, Malay, Indonesian, and implied probability percentage — all seven major formats.
Enter the odds from a specific market. The calculator shows the fair no-vig probability for each outcome. Compare those fair probabilities to your own estimates — if your estimated probability is higher than the fair probability, you have a potential value bet.
If your estimated win probability is below the break-even implied by the odds, Kelly outputs a negative result — meaning don't bet. That automatic filter is one of the formula's most useful properties.