Betting Calculators

Free tools for smarter betting. Convert odds, calculate arbitrage profit, find bookmaker margins, and size your bets with the Kelly Criterion.

Odds Converter

Enter any odds format and instantly see the equivalent in all other formats, plus the implied probability.

American: —Fractional: —Implied Probability: —

Arbitrage Profit Calculator

Enter the best odds for each outcome to calculate your guaranteed profit. The calculator divides your total stake proportionally across all outcomes.

Enter odds and stake, then click Calculate.

Kelly Criterion Calculator

Calculate the optimal bet size based on your estimated probability and the odds offered. The Kelly Criterion maximizes long-term bankroll growth while minimizing risk of ruin.

Enter odds, probability, and bankroll, then click Calculate.

Payout Calculator

Quickly calculate your potential profit, total payout, and return on investment (ROI) for any bet. Enter decimal odds and your stake.

Enter odds and stake, then click Calculate.

3-Way Arbitrage Calculator (Soccer / Football)

For events with three outcomes — Home Win, Draw, Away Win — like soccer matches. Enter the best odds from different bookmakers for each outcome to find guaranteed profit.

Enter odds for all three outcomes and stake, then click Calculate.

Overround & Margin Calculator

Calculate the bookmaker's margin (overround/vig) for any market. See implied probabilities, the bookmaker's edge, and fair odds with vig removed.

Enter odds for all outcomes and click Calculate Margin.

Formulae Explained

Odds Conversion

  • Decimal to American: If decimal >= 2.00 → +((decimal - 1) * 100). If decimal < 2.00 → -(100 / (decimal - 1)).
  • Decimal to Implied Probability: (1 / decimal) * 100%
  • American to Decimal: If positive → (American / 100) + 1. If negative → (100 / |American|) + 1.

Payout Calculation

  • Profit: stake × (decimal - 1)
  • Total Payout: stake × decimal
  • ROI: (decimal - 1) × 100%

Arbitrage Profit

  • Combined implied probability (2-way): (1 / odds₁) + (1 / odds₂) — must be below 1.0 (100%)
  • Combined implied probability (3-way): (1 / odds₁) + (1 / odds₂) + (1 / odds₃) — must be below 1.0 (100%)
  • Profit %: (1 / combined_implied - 1) * 100%
  • Stake per outcome: (total_stake * (1 / odds_n)) / combined_implied

Overround & Vig

  • Overround: total implied probability - 100% — the bookmaker's built-in edge
  • Fair odds: actual odds × total implied probability — removes the vig to show true probability odds
  • A market with 0% overround is "fair" — negative overround indicates arbitrage

Kelly Criterion

  • Fraction: f* = (b * p - q) / b, where b = net odds (decimal - 1), p = win probability, q = 1 - p
  • Optimal stake: bankroll * f*
  • Half Kelly: Often recommended to reduce variance — stake half the Kelly fraction.

← Back to Arbitrage Scanner