Free Matched Betting Calculator & Promotion Tracker
Calculate your lay stakes and guaranteed profit, then find today's best bookmaker promotions — all completely free.
What is a matched betting calculator?
A matched betting calculator is the single most important tool in matched betting. It tells you the exact lay stake to place at the Betfair Exchange so that every possible outcome of an event is covered, locking in either a small qualifying loss (typically 2–8%) or a guaranteed profit from a bonus bet (typically 70–80% of face value). Use the Normal mode for cash qualifying bets, Free Bet (SNR) for standard Australian bonus bets where the stake is not returned, and Free Bet (SR) for the rarer offers where the stake is paid back on a win.
It's the same tool people search for under a few different names — lay calculator, lay bet calculator, back and lay calculator, bonus bet calculator or simply a betting calculator. One tool covers all of them: give it your back stake, back odds, lay odds and exchange commission, and it returns your lay stake, liability and the profit locked in for both outcomes.
What each calculator mode is used for
Rather than juggling separate tools, the three modes above cover every situation an Australian matched bettor runs into:
- Lay stake calculator — the core job. Works out exactly how much to lay at the exchange so the bookmaker bet is fully covered, and shows the liability you need available before you place it.
- Qualifying bet calculator — use Normal mode with your own cash to see the qualifying loss before you commit. Anything under about 5% of stake is fine when it unlocks a larger bonus.
- Bonus bet calculator — use Free Bet (SNR) to convert an Australian bonus bet into cash, and Free Bet (SR) for stake-returned promos. Higher back odds extract more from an SNR bonus.
- Commission handling — Betfair Australia takes 5% of net winnings, which is already factored into the lay stake so the profit figures you see are the ones that land in your account.
New to backing and laying? Start with what matched betting is and how qualifying bets work before running your first calculation.
Worked example: $50 qualifying bet
You back West Ham vs Brighton at 1.94 on Sportsbet with a $50 stake. Betfair's lay odds are 1.99 and Aussie commission is 5%. The calculator returns:
- Lay stake: $50.00
- Liability: $49.50 (the amount you need in your Betfair wallet)
- If back wins: −$2.50
- If lay wins: −$2.50
- Guaranteed qualifying loss: $2.50 (5% of stake — acceptable)
Sportsbet then credits a $150 SNR bonus bet. Switch the calculator to Free Bet (SNR), find higher odds (around 5.0), and the same maths returns roughly $112 of locked-in profit — a 75% extraction rate. See the full walk-through in our matched betting guide.
How the back/lay maths works
The calculator solves a simple system of two equations: profit if the back bet wins must equal profit if the lay bet wins. The closed-form solutions are:
- Normal / SR: lay stake = (back stake × back odds) ÷ (lay odds − commission)
- SNR free bet: lay stake = (back stake × (back odds − 1)) ÷ (lay odds − commission)
- Liability: lay stake × (lay odds − 1)
The SNR formula uses (back odds − 1) because you don't get the stake back if the bonus bet wins — only the winnings count. That single change is why SNR free bets extract less value than SR free bets at the same odds.
When to use each mode
| Mode | Use for | Typical extraction |
|---|---|---|
| Normal | Cash qualifying bets and any bet placed with your own money | Locks in 2–8% qualifying loss |
| Free Bet (SNR) | Standard Aus bonus bets — Sportsbet, Ladbrokes, Neds, BetEasy, etc. | 70–80% of bonus value |
| Free Bet (SR) | Rarer "stake returned" bonuses and bonus cash promotions | ~95% of bonus value |
Frequently asked questions
What is a matched betting calculator?
A matched betting calculator works out the exact lay stake you need to place at the Betfair Exchange to fully cover a back bet at a bookmaker. It removes all variance and tells you the guaranteed profit (or qualifying loss) before you place a single bet.
How does the matched betting calculator formula work?
For a normal qualifying bet, lay stake = (back stake × back odds) ÷ (lay odds − commission). For a Stake Not Returned (SNR) free bet, lay stake = (back stake × (back odds − 1)) ÷ (lay odds − commission). For a Stake Returned (SR) free bet, the formula matches the normal bet because the stake is paid back on a win.
What is the difference between SNR and SR free bet modes?
SNR (Stake Not Returned) is the most common Australian bonus bet — you only keep the winnings if the bet wins. SR (Stake Returned) means the stake is also paid back on a win. SNR typically extracts 70–80% of face value; SR extracts close to 95%.
What lay commission should I enter for Australia?
Betfair Australia charges 5% commission on net winnings on the exchange, so 5% is the correct default for almost every Australian matched bettor. Some users on Betfair's Premium Charge or Charge 2 should enter their effective rate.
What is liability?
Liability is the amount you must have available in your Betfair Exchange wallet to cover a lay bet if it loses. It is calculated as lay stake × (lay odds − 1).
Why is my qualifying bet showing a small loss?
A small qualifying loss (typically 2–8% of stake) is normal and expected. The bookmaker and exchange odds rarely match exactly, so you sacrifice a few dollars on the qualifier to unlock a much larger bonus bet.
Is the matched betting calculator free?
Yes. Our calculator is completely free, runs entirely in your browser, requires no signup and works on desktop and mobile.
Can I use it for partial lays or underlaying?
The calculator solves for a fully matched lay. For underlay or overlay strategies, simply enter a smaller or larger lay stake than the calculated value — the result rows will show how the outcome shifts in each direction.
What is a lay calculator?
A lay calculator (also called a lay bet calculator or lay stake calculator) works out how much to stake against a selection at a betting exchange so your bookmaker back bet is fully covered. Enter your back stake, back odds, lay odds and exchange commission, and it returns the lay stake, the liability you need in your exchange wallet, and your profit or loss in each outcome.
How do I calculate my lay stake?
For a cash bet, lay stake = (back stake × back odds) ÷ (lay odds − commission). Using a $50 back at 3.50, lay odds of 3.60 and 5% Betfair commission: (50 × 3.50) ÷ (3.60 − 0.05) = $49.30. For an SNR bonus bet, replace back odds with (back odds − 1) because the stake is not returned.
How does a back and lay calculator work?
A back and lay calculator equalises the two possible results. It solves for the lay stake where your profit if the bookmaker bet wins equals your profit if the lay bet wins, after deducting exchange commission. Because both outcomes return the same figure, you know your result before the event starts — that is what makes matched betting low risk rather than gambling.
How do I calculate a bonus bet's value?
Switch the bonus bet calculator to Free Bet (SNR), enter the bonus bet amount as the back stake, then enter the back and lay odds for a high-odds selection. Guaranteed profit is roughly bonus amount × (back odds − 1) ÷ back odds after commission, which is why higher odds extract more. A $100 SNR bonus bet at odds near 5.0 usually returns $75–$80 in cash.
Is this the same as a betting calculator or odds calculator?
A generic betting calculator only works out a potential return from odds and stake. This is a matched betting calculator: it handles both sides of the bet — the back bet at the bookmaker and the lay bet at the exchange — plus commission and liability, so it shows guaranteed profit rather than potential winnings.
Do I need a different calculator for bonus bets and qualifying bets?
No. The same tool covers all three cases. Use Normal for qualifying bets placed with your own cash, Free Bet (SNR) for standard Australian bonus bets, and Free Bet (SR) for stake-returned bonuses and bonus cash. Only the lay stake formula changes; the inputs stay identical.