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OddsRelay

Bookmaker margin & fair-odds calculator

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See the margin baked into a market and the true, no-vig prices.

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Every bookmaker builds a margin into their prices, so the implied probabilities of a market add up to more than 100%. Enter the odds for each outcome to see that margin, and the fair (no-vig) odds you'd get if it were stripped out — a quick way to judge whether a price is sharp and to compare books.

What it does

  • Bookmaker margin (overround) for the whole market
  • No-vig fair odds and probability for each outcome
  • Implied vs fair probability, side by side
  • Spots an underround (negative margin) where the market is in your favour

How to use it

  1. 1Enter every outcome's odds. Add the decimal odds for each outcome in the market.
  2. 2Read the margin. See the total implied probability and the bookmaker's margin.
  3. 3Compare fair odds. The table shows the no-vig fair odds and probability per outcome.

What powers this

This calculator runs entirely in your browser. There's no account, no API key and no feed — nothing you type leaves the page. The maths is the same commodity matched-betting and value arithmetic used across the industry, implemented carefully and unit-tested.

Questions

What is a bookmaker's margin?
The margin (or overround / vig) is the edge a bookmaker builds into their prices. Add up the implied probabilities of every outcome — the amount over 100% is the margin.
What are no-vig fair odds?
Fair odds are the prices with the margin removed proportionally, so the probabilities sum to exactly 100%. They're the market's best estimate of the true chances, useful for spotting value.
Can the margin be negative?
Yes — if the implied probabilities add up to under 100% it's an underround, and backing every outcome would guarantee a profit. That's the arbitrage case, and it's rare.

18+ · Data product for licensed operators. Please gamble responsibly.

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