The Exchange calculator is your go-to tool for backing an outcome at a bookmaker and laying the same outcome at an exchange to guarantee a profit or minimise losses.

When to use it

You'll use the Exchange calculator whenever you're:

• Converting bonus bets into cash by backing an outcome at a bookmaker and laying it off at an exchange
• Taking advantage of risk-free bet promotions
• Matched betting on a single outcome
• Hedging an existing position

Understanding the inputs

Bet Type

The calculator supports two bet types:

• SR (Stake Returned): Traditional bets where your stake is returned along with your winnings.
• SNR (Stake Not Returned): Bonus bets where only the profit is returned, not the original stake. Most bookmaker promotions are SNR.

This distinction is critical because it dramatically affects your profit calculations. An SNR bet at 3.0 returns $200 on a $100 stake (not $300), while an SR bet returns $300 total.

Back details

• Back Stake: The amount you're betting at the bookmaker.
• Back Odds: The odds offered by the bookmaker.
• Back Commission: Some exchanges and betting platforms charge commission on winning back bets. Most bookmakers don't, so this is usually 0%.

Lay details

• Lay Odds: The odds at which you can lay (bet against) the same outcome at the exchange. These are typically slightly higher than the back odds.
• Lay Commission: The commission charged by the exchange on winning lay bets. Betfair typically charges 2-5% depending on your discount rate.

Understanding the outputs

The calculator provides three key numbers:

1. Lay Stake: The exact amount you need to lay at the exchange to achieve your desired profit distribution. This is the most important number - you'll need sufficient liquidity available at the lay odds to place this stake.

2. Liability: The amount you need in your exchange account to place the lay bet. This is what you'll lose if the back bet wins. Think of it as your risk exposure at the exchange.

3. Profit: Your guaranteed net return regardless of outcome when the slider is at 50% (balanced). This is the beauty of matched betting - you lock in a profit either way.

If the back bet wins

Your bookmaker pays out, but you lose your liability at the exchange.

If the lay bet wins

You lose your back stake at the bookmaker, but you win your lay bet at the exchange (minus commission).

Overlaying and underlaying

The slider at the bottom lets you adjust your risk/reward profile:

• 50% (Balanced): Equal profit regardless of outcome. This is the default matched betting approach.
• Below 50% (Underlaying): Reduces your lay stake, lowering your liability and increasing profit if the back bet wins. You'll make less (or lose money) if the lay bet wins. Useful when you're confident in your back bet or want to reduce exchange exposure.
• Above 50% (Overlaying): Increases your lay stake, raising your liability but increasing profit if the lay bet wins. You'll make less (or lose money) if the back bet wins. Less common but useful in specific arbitrage scenarios.

Practical example

You receive a $50 SNR bonus bet from TAB. You find a horse racing market where:

• TAB offers 4.0 back odds
• Betfair offers 4.2 lay odds with 5% commission

Enter these values:

• Bet Type: SNR
• Back Stake: $50
• Back Odds: 4.0
• Back Commission: 0%
• Lay Odds: 4.2
• Lay Commission: 5%

The calculator shows:

• Lay Stake: $36.14
• Liability: $115.66
• Profit: $34.34 (regardless of outcome)

You've just converted ~75% of your bonus bet value into cash, guaranteed.

Common issues

The lay odds changed before I could place my bet. What should I do?

You have two options:

1. Submit anyway: Place your lay bet at the original odds. The exchange will hold it in the queue and match it if/when those odds become available again. This is fine if you're not in a rush, but be sure to monitor how the lay odds move.
2. Recalculate: Update the lay odds in the calculator and check if the new profit is still acceptable. If the odds moved against you (increased), your profit will be lower. If they moved in your favor (decreased), your profit will be higher.

I don't have enough in my Betfair account to cover the liability. What are my options?

You have several approaches:

1. Deposit more funds: The simplest solution if you have the cash available.
2. Underlay: Drag the slider below the balanced mark to reduce your lay stake and liability. This creates a two outcome profit scenario where you make more if the back bet wins, but less (or a loss) if the lay bet wins.
3. Split your bonus bet: Many bookmakers let you split bonus bets into smaller chunks. Place multiple smaller matched bets instead of one large one.
4. Choose a different market: Look for markets with lower lay odds, which reduce liability.