Understanding bookie margin and calculating fair price

If you want to become a profitable punter, understanding the bookie margin and how to calculate the fair price of a market are super important concepts.

In this article we will cover everything you need to know about how bookies make money, how to better understand what prices mean and how to calculate the fair price.

What is the bookie margin?

When bookmakers offer odds, they are meant to reflect the probability of the event occurring. In a perfectly fair market on a 50/50 event, you’d see odds of 2.00/2.00. In reality you see 1.90/1.90. That difference is the bookie margin — it’s how bookmakers make money.

Calculating the margin with two odds

The formula: (1/Odds1) + (1/Odds2). This will always be greater than 100% for any bookmaker.

For example, Sportsbet offering 2.00 and 1.85: 1/2 + 1/1.85 = 104.5%. Punters lose ~4% on average on head-to-head markets. Taking the best prices across all books reduces this significantly — getting 2.02 and 1.91 gives 101.9%.

Player props have higher margins

On prop markets the margin is typically 6-9%. A Sportsbet prop at 1.96/1.80 gives 106.58%. Taking best prices across books (1.98/1.88) reduces this to 103.70%.

Three-way and multi-runner markets

Adding more outcomes increases the bookmaker’s edge significantly. A three-way market at 1.61/5/3.80 gives 108.43%. Horse racing win markets regularly run at 120-125% overround — meaning punters lose 20-25% on average without an edge. This is why serious punters avoid multi-leg exotic markets.

Why this matters for profitable betting

Understanding margin is the foundation of every profitable betting strategy. Arbitrage betting, positive EV betting, and middles all rely on finding prices that beat the true market probability. The Betsniper calculators help you calculate fair prices instantly, and the Positive EV tool automatically identifies where Australian bookmaker prices are out of line with the true market.