Back/Lay Hedging Calculator (Exchange)

Betting exchanges such as Betfair, Matchbook, and Smarkets let you act like the bookmaker. You can back a selection to win, or lay the same selection by betting against it.

Traders and matched bettors use back/lay hedging when odds move. If you backed at a higher price and can later lay at a lower price, you may be able to create a green book, meaning a positive or near-equal result whichever way the selection settles.

This Back/Lay Hedging Calculator estimates the lay stake required to hedge a back bet. It shows the exchange liability, profit if the selection wins, profit if it loses, and the impact of commission.

Important: this calculator assumes the lay bet is fully matched at the entered price and that the back and lay bets settle under compatible rules. Odds movement, market suspension, rejected stakes, voids, and commission differences can change the final result.

How to Use the Back/Lay Hedging Calculator

1. Select the mode:
   • Cross Exchange: use this when the back bet is with a bookmaker and the lay bet is on an exchange.
   • Same Exchange: use this when both the back and lay bets are on the same exchange and commission can affect both winning sides.
2. Enter the back bet: Add your original back stake and decimal back odds.
3. Enter the lay bet: Add the current exchange lay odds and commission rate.
4. Read the result: The calculator shows the lay stake, liability, and profit or loss in both outcomes.

Back/Lay Hedge Formula

For a standard bookmaker-to-exchange hedge, the lay stake is calculated as:

Lay Stake = (Back Stake × Back Odds) ÷ (Lay Odds – Commission)

Commission is entered as a decimal rate inside the formula. For example, 2% commission is 0.02.

The two outcomes are then:

• If the selection wins: back bet wins, lay bet loses, and you pay the exchange liability.
• If the selection loses: back bet loses, lay bet wins, and exchange commission is deducted from the lay winnings.

Worked Example: Back High, Lay Low

Suppose you back a horse at odds of 4.00 with a $100 stake. Later, the market moves and you can lay the same horse at 3.00 on an exchange with 2% commission.

• Back stake: $100
• Back odds: 4.00
• Lay odds: 3.00
• Commission: 2%

The calculator estimates a lay stake of about $134.23. Your exchange liability is about $268.46. If both bets are matched at those prices, the result is approximately equalized: about $31.54 profit whether the horse wins or loses.

When the Hedge Locks in a Loss

If the lay odds are higher than the back odds, hedging may still reduce risk, but it can lock in a loss. For example, backing at 3.00 and laying at 4.00 usually creates a negative hedge unless there is another reason to trade out.

This can still be rational if you are reducing exposure after new information, but it should not be described as a green book. The calculator shows the minimum outcome so you can see whether the hedge is positive, near break-even, or negative.

Cross Exchange vs Same Exchange

Important Execution Risks

Back/lay hedging depends on execution. A calculation can look profitable, but the trade can fail if the exchange lay bet is not fully matched, the price moves, the market is suspended, the bookmaker voids one side, or settlement rules differ.

Always confirm the lay bet has been fully matched and that your exchange account has enough balance to cover the liability.

Frequently Asked Questions