Bonus bet converter calculator
Enter a bonus bet, the bookmaker's odds and the exchange's lay odds. The calculator works out how much to lay, the liability, and the cash you would keep either way if both bets are matched at those prices, after commission. Free, with no account needed.
Your bet
Enter the back bet you're placing at the bookmaker and the lay odds available at the exchange.
A bonus bet where only the winnings are paid out. The lay locks in a share of the bonus as cash.
What to lay
Place this lay at the exchange and your result is the same whichever way the bet goes.
Fill in your bet details to see the lay stake.
Betting involves risk. Bookmakers can restrict or close accounts and void bets, automation can fail, prices move, and a positive expected value (+EV) bet can still lose. Promotions carry each bookmaker's own terms. There is no guarantee of profit. The result assumes both bets are matched in full at the prices you enter. See responsible gambling for limits and support.
How the conversion maths works
Converting a bonus bet means using it to back a selection at a bookmaker, then laying the same selection on a betting exchange, so you end up with about the same cash whichever way the result goes. It is the back-and-lay calculation matched betting is built on, with one change: the bonus bet's stake is not returned.
A stake-not-returned bonus bet that wins pays the bonus bet amount times the back odds minus one. The lay stake is set so that what the lay wins, after commission, equals that payout less the lay's liability. That gives four formulas:
Lay stake = bonus bet × (back odds - 1) ÷ (lay odds - commission rate)
Liability = lay stake × (lay odds - 1)
Cash kept either way = lay stake × (1 - commission rate)
Conversion = cash kept ÷ bonus bet
Write the commission rate as a decimal, so 5% is 0.05. The calculator rounds the lay stake to the cent, so the two outcomes can differ by a cent or two.
Reading the result
- Lay stake: how much to lay on the exchange, at the lay odds you entered.
- Liability: what you pay out at the exchange if the selection wins. The exchange holds it until the market settles.
- The table: your result at the bookmaker, at the exchange and overall, for each outcome. The percentage under it is your conversion.
- The slider: the result if you lay more or less than the recommended stake, for example to meet an exchange minimum.
Worked example
Take a $50.00 stake-not-returned bonus bet used on a selection at $6.00 with the bookmaker, and a lay price of $6.20 on the exchange with 5% commission. These numbers are hypothetical.
- If the selection wins, the bonus bet pays $50.00 × (6.00 - 1) = $250.00. The stake is not returned.
- Lay stake: $250.00 ÷ (6.20 - 0.05) = $40.65.
- Liability: $40.65 × (6.20 - 1) = $211.38.
- Either way you keep $38.62, which is 77.2% of the bonus bet.
| Outcome | Bookmaker | Exchange | Overall |
|---|---|---|---|
| The selection wins | $250.00 | -$211.38 | $38.62 |
| The selection loses | $0.00 | $38.62 | $38.62 |
Commission, price movement and liquidity
The calculator is exact for the prices you enter. What happens at the exchange can differ.
Exchange commission
A betting exchange charges commission on winnings. The calculator takes the rate you enter off the lay's win and sizes the lay so the cost is shared across both outcomes. In the worked example, 5% takes $2.03 off the lay's win, and the bonus bet keeps $38.62 instead of the $40.32 it would keep with no commission.
Enter the rate your own exchange account pays; the calculator starts at 5% as an example. Commission is usually charged on your net winnings in a market, so other bets you hold in the same market can change what you pay.
Price movement
Prices can move between placing the bonus bet and placing the lay. If the lay price changes, enter the new one: the lay stake and the cash you keep both change. For the same $50.00 bonus bet at $6.00, a lay at $6.00 keeps $39.90 (79.8%) and a lay at $7.00 keeps $34.17 (68.3%).
Liquidity and minimum stakes
A lay is matched only against money other exchange users have offered at your price. If there is not enough, part of it can go unmatched, leaving that part of the bonus bet unhedged. An exchange can also set a minimum stake. The slider shows the result of laying more or less than the recommended stake.
Liability
You need enough in your exchange account to cover the liability: $211.38 to convert a $50.00 bonus bet in the worked example. It grows with the lay price.
Settlement rules
The bookmaker and the exchange each settle under their own rules. A dead heat, a deduction after a late scratching, or a bet voided on one side and not the other can leave the two bets out of balance.
How bonus bets work, and why they pay less
A bonus bet is a credit a bookmaker adds to your account that can only be used to place a bet. It cannot be withdrawn as cash. Each bookmaker sets its own terms, which can include an expiry date, a minimum price and limits on the markets it can be used on, so read them before you use one.
The term that matters most for its value is whether the stake comes back. A stake-not-returned bonus bet that wins pays the winnings only: $50.00 at $6.00 pays $250.00, where a $50.00 cash bet at the same price returns $300.00, the same winnings plus your stake. If it loses, you lose the bonus bet but no cash.
That missing stake is why a bonus bet is worth less than its face value, and why short prices cost the most: at $2.00 the stake is half of what a cash win returns, and at $11.00 it is one eleventh.
Bonus bets are issued by bookmakers under their own terms; B337 never creates or claims them.
Bookmaker and Betfair prices side by side
The calculator needs two prices for the same selection: the bookmaker's, and the exchange's lay price.
The Terminal, B337's odds comparison board, shows Betfair back and lay prices beside odds from 40+ bookmakers across racing and sports, with price history and closing lines. See odds comparison for what it covers.
See Betfair lay prices beside 40+ bookmakers
In a free account the Terminal's Betfair back and lay prices are locked. Terminal View, $25 a month, unlocks:
- Betfair back and lay prices beside the bookmaker prices
- Live odds from 40+ bookmakers, racing and sports
- Price history (flucs) and closing lines
- EV overlays on the odds
For racing, B337's automated betting can use the bonus bets already in your own bookmaker accounts. A session places a bonus bet only where its conversion against the Betfair price clears the threshold you set, and tracks stake, return and conversion per session and per bookmaker. It runs on your own computer, in accounts you hold. See bonus bet automation.
Betting involves risk. Bookmakers can restrict or close accounts and void bets, automation can fail, prices move, and a positive expected value (+EV) bet can still lose. Promotions carry each bookmaker's own terms. There is no guarantee of profit. See responsible gambling for limits and support.
Questions about converting bonus bets
How do I convert a bonus bet to cash?
Use the bonus bet to back a selection at the bookmaker, then lay the same selection on a betting exchange with the lay stake the calculator gives you. If both bets are matched at those prices, you end up with about the same cash whichever way the result goes, less exchange commission. Prices can move between the two bets, so check the lay price again before you place it.
Which odds convert a bonus bet best?
Longer odds keep more, as long as the back and lay prices stay close, because the missing stake is a smaller share of what a win pays. Laid at the bookmaker's own price with no commission, a $50.00 bonus bet keeps $25.00 (50.0%) at $2.00 and $45.45 (90.9%) at $11.00. The liability grows with the price too: $25.00 at $2.00 against $454.50 at $11.00.
Do I have to lay a bonus bet?
No. Left alone, a bonus bet either pays its winnings or pays nothing. Laying it swaps that swing for a smaller amount that is about the same either way, at the cost of commission and any gap between the back and lay prices.
Does it work for bonus bets that return the stake?
No. Bonus bet mode assumes the stake is not returned, so it undervalues a bonus bet whose terms give the stake back, and Normal bet mode assumes your own cash is at risk, so neither fits one.
Do I need an account to use the calculator?
No. The calculator is free and works in your browser. A free account opens a limited view of the Terminal with live odds; Betfair prices unlock with a paid plan.
Is B337 a bookmaker, and does it give out bonus bets?
No. B337 is software, not a bookmaker or wagering service provider. Bets are placed in accounts you hold with Australian bookmakers. Bookmakers issue bonus bets under their own terms, and B337 never creates or claims them.
Can B337 use my bonus bets automatically?
For racing, yes: a session can place the bonus bets already in your own accounts where the conversion against the Betfair price clears a threshold you set. See bonus bet automation. Many bookmakers restrict or prohibit automated betting, so read their terms before you connect an account.
Related pages
Start with a free account
A free account opens a limited view of the Terminal with live odds. Terminal View adds Betfair back and lay prices beside 40+ bookmakers, and automated betting adds racing sessions that use the bonus bets already in your own bookmaker accounts, on the rules you set.
By the B337 team. Last updated .