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Odds Calculator

Enter your estimated probability, the offered odds, and your stake to evaluate expected return, break-even points, and optimal sizing.

Decimal between 0 and 1 (e.g., 0.55).

Converts other markets to decimal & probability.

Expected Value per Bet

$-5.50

Positive values indicate +EV bets

Break-even Win Rate

47.62%

Compare to your estimated probability

Edge (Your P − Break-even P)

-2.62%

Positive edge implies value

Implied American Odds

110

Equivalent moneyline for decimal odds

Potential Profit

$110.00

If the bet wins

Kelly Stake (fraction of bankroll)

0%

Suggested bet size for growth (0 if negative edge)

Custom American odds of 110 imply decimal odds of 2.100 and a break-even probability of 47.62%.

How to Use This Calculator

  1. Estimate your true win probability for a bet based on models or intuition.
  2. Enter the bookmaker's decimal odds and your intended stake.
  3. Compare your probability to the break-even probability to determine value.
  4. Use the expected value and Kelly fraction to size positions responsibly.

Formula

Break-even P = 1 / Decimal

EV = P · Stake · (Decimal − 1) − (1 − P) · Stake

Kelly fraction = (P · Decimal − 1) / (Decimal − 1)

Kelly sizing maximizes long-term growth under ideal assumptions. Many bettors wager a fraction of the Kelly recommendation to reduce variance.

Full Description

Betting edges emerge when your probability estimate exceeds the bookmaker's implied probability. This calculator quantifies that edge and shows how it translates into expected profit and optimal bet sizing. It supports bankroll management, arbitrage checks, and ROI comparisons across markets.

The custom American odds converter lets you analyze competing lines in different formats. Combine this tool with implied probability conversions to normalize odds across sportsbooks.

Frequently Asked Questions

What if my edge is negative?

A negative edge means the bet has negative expected value. Consider skipping it or searching for better odds.

Should I always bet the Kelly amount?

Full Kelly maximizes growth but is volatile. Many bettors use half-Kelly or fixed units to manage drawdowns.

How accurate must my probability be?

Small errors near break-even can flip a positive EV into a negative one. Use conservative estimates and maintain a margin of safety.

Can I analyze parlays?

Yes. Convert the parlay payout into decimal odds and estimate the combined probability before entering the values here.