This Back/Lay Hedging Calculator finds the lay stake needed to balance a cash back bet. It shows the exchange liability and estimated profit or loss if the selection wins or loses, using either a bookmaker-to-exchange hedge or two bets in the same exchange market.
The commission model matters. A bookmaker back bet and an exchange lay are settled separately; back and lay bets in one exchange market are combined before ordinary winning-market commission is charged.
Choose your hedge and commission model
Calculate the lay stake, liability, and P/L for a back/lay hedge.
Back Bet
Lay Bet
Liability and outcome P/L use the displayed lay stake rounded to cents. Both bets must be fully matched.
What went wrong?
How to calculate a back-and-lay hedge
- Choose Cross Exchange for a cash back bet at a bookmaker and a lay on an exchange. Choose Same Exchange when both bets are in the same exchange market.
- Enter the back stake, decimal back odds, available lay odds and your effective commission percentage.
- Read the lay stake, liability and both outcome results. These use the displayed lay stake rounded to cents.
All amounts must use the same currency. Changing the currency symbol does not convert balances or odds. If you have American or fractional prices, use the odds converter first.
Lay stake and liability are different amounts
A back bet wins when the selection wins. A lay bet wins when that selection loses. The lay stake is the amount you can win from the backer before commission; liability is what you owe if your lay loses.
Liability = lay stake × (lay odds − 1)
A $100 lay stake at 3.00 creates $200 liability. You need funds for that liability on the exchange, in addition to the cash already committed to the back bet.
Choose the correct commission model
In the formulas below, S is the cash back stake, B the decimal back odds, O the decimal lay odds and c the commission rate as a decimal. Enter 2 in the calculator for 2%; use 0.02 in the formula.
Cross Exchange: bookmaker back and exchange lay
This mode assumes no commission on the bookmaker back bet and commission on the exchange lay winnings. The equalizing lay stake is:
L = S × B ÷ (O − c)
If the selection wins: S × (B − 1) − L × (O − 1)If the selection loses: L × (1 − c) − S
Although the button is called Cross Exchange, it models a bookmaker and one exchange. Two exchanges charging separate commission rates require a different calculation.
Same Exchange: both bets in one market
For these two positions in the same market, first balance the result before commission:
L = S × B ÷ O
Combine the winning and losing bet results for each outcome, then deduct commission only from a positive market profit:
After-commission P/L = market P/L − c × max(market P/L, 0)
The commission rate does not change the unrounded equalizing stake in this model. It reduces a positive result after netting. A losing market incurs no ordinary winning-market commission. Other positions in the market would change the commission calculation.
Example 1: pre-race trading
You back a horse for $100 at 4.00 and can later lay it at 3.00. With 2% commission, the Back/Lay Hedging Calculator gives these results:
| Placement | Lay stake | Liability | Selection wins | Selection loses |
|---|---|---|---|---|
| Bookmaker + exchange | $134.23 | $268.46 | +$31.54 | +$31.55 |
| Same exchange market | $133.33 | $266.66 | +$32.67 | +$32.66 |
The difference comes from where commission is charged. In the second row, the back and lay results offset within one market before the fee is calculated. The one-cent difference between outcomes comes from rounding the lay stake.
Example 2: a cash qualifying bet
Back $50 at bookmaker odds of 2.10, then lay at 2.15 with 5% exchange commission. Cross Exchange mode gives a $50.00 lay stake and $57.50 liability.
- If the selection wins, the back profit is $55.00 and the lay liability is $57.50: −$2.50.
- If the selection loses, the back bet loses $50.00 and the lay returns $47.50 after commission: −$2.50.
This is the cost of the cash hedge. Any promotional reward is separate; it is not included in either outcome.
Example 3: closing a failed trade
You back $100 at a bookmaker at 3.00, but the available lay odds drift to 4.00. At 2% commission, Cross Exchange mode gives a lay stake of $75.38 and liability of $226.14.
The selection winning produces −$26.14; it losing produces about −$26.13. Hedging balances the exposure at a loss. It does not recover the original position’s value.
If you want to hedge by backing the opposing outcome rather than laying the original selection, use the two-outcome hedging calculator.
Matching, liquidity and settlement
The result assumes the full back and lay stakes are matched at the entered prices and settle under compatible rules. Check the available size at the lay price: a partial fill leaves part of the position exposed, and several fills at different odds need to be combined.
Suspensions, voids, dead heats, non-runner reductions and different settlement rules can change the result. The calculator rounds the lay stake to cents before calculating liability and P/L; platform minimum stakes, settlement rounding, additional charges and taxes can also affect execution.
A positive estimate describes the entered pair of bets. It does not establish that an ongoing trading strategy is profitable.
Frequently asked questions
What is a green book?
A green book is a position showing a positive result across the relevant market outcomes. For a fully matched back-and-lay pair on one selection, check that both displayed outcomes are positive.
Does commission apply to a losing lay bet?
In Cross Exchange mode, the losing lay pays its liability without a winning-bet commission deduction. In Same Exchange mode, ordinary commission depends on the combined market result, including the back bet.
Can I use this for matched betting?
Yes, for the cash qualifying bet. Use Cross Exchange when backing with a bookmaker and laying on an exchange. Promotional eligibility, rewards and withdrawal conditions are outside the calculation.
Does it calculate stake-not-returned free bets?
No. A cash back stake is returned as part of a winning back bet. A stake-not-returned free bet changes that payoff and needs a different formula.
Can I enter two different exchange commission rates?
No. Same Exchange assumes one market and one net-profit commission rate. Cross Exchange assumes an uncharged bookmaker back and one exchange lay rate.
Can I use the calculator during an event?
Yes, but the entered lay price must still be available when the bet is matched. In-play delays and rapidly changing liquidity can leave the executed position different from the estimate.
What if only part of my lay bet is matched?
The displayed hedge assumes the entire lay stake is matched. An unmatched remainder is not protection; recalculate using your actual matched position and the prices available for any remaining hedge.
Why are the two outcome profits sometimes different?
The formula balances an unrounded stake. Currency stakes use cents, so the Back/Lay Hedging Calculator recalculates both outcomes after rounding the lay amount. At higher odds, that imbalance can exceed one cent.
Do lower lay odds always guarantee a profit?
No. Separate exchange commission can outweigh a small price improvement. For example, a $100 bookmaker back at 2.00 and a lay at 1.99 with 5% commission produces about a $2.06 loss per outcome.
Is a negative hedge result an error?
No. A hedge can balance a loss when the available prices are unfavorable. Compare both outcomes with the exposure you would retain by leaving the original bet open.
Sources
- Betfair — Exchange commission: ordinary commission is charged on net market winnings.
- Smarkets — How to calculate a hedge bet: same-exchange hedge sizing and the distinction when using separate operators.