Free betting tools
Betting math, done for you.
Convert odds, find value, and size stakes responsibly. No signup required.
Value bet calculator
Enter the model probability and the odds to see expected value.
%
Expected value
+18.9%
Expected profit
+0.19u
EV = (probability × odds) − 1. A positive result means the price offers value at your estimated probability. Edge +18.9% relative to stake.
Odds converter
Convert between decimal, American, fractional and implied probability.
Decimal2.05
American+105
Fractional21/20
Implied probability48.8%
Implied probability calculator
Turn decimal odds into a true win probability.
Implied probability
48.8%
Implied probability = 1 ÷ decimal odds. This is the bookmaker price before margin.
Kelly criterion calculator
Optimal stake sizing with fractional Kelly (0.25x default).
%
Recommended stake
4.5%
Stake amount
45.00
Full Kelly = (b·p − q) ÷ b, where b = odds − 1, q = 1 − p. A negative result means no edge — no bet. Fractional Kelly reduces variance; most bettors stake a quarter or less.
Bankroll & stake calculator
Recommended unit size and stake for your risk profile.
%
1 unit
20.00
This stake
20.00
A flat-stake unit of 1–3% of bankroll is a common, conservative discipline. Smaller units survive longer downswings. Never stake money you cannot afford to lose.
These tools are informational and never guaranteed. Outputs depend entirely on the inputs you provide. Bet responsibly and only where legal. 18+