Free Tool

Matched Betting Calculator

Calculate your exact lay stake and guaranteed profit for qualifying bets, free bets (SNR), and free bets (SR).

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Advanced: Underlay / Overlay
Underlay -50% 0% Overlay +50%

0% = equal profit/loss regardless of outcome. Underlay shifts more profit to if the back bet wins. Overlay shifts more profit to if the lay bet wins.

Enter your bet details above to see results

How To Use This Calculator

  1. 1

    Choose Your Mode

    Select "Qualifying Bet" for sign-up offers where you need to place a real bet first. Select "Free Bet (SNR)" when using a free bet where the stake is not returned. Select "Free Bet (SR)" when the free bet stake is returned with winnings.

  2. 2

    Enter the Back Stake

    Type the amount you're placing (or the value of your free bet) at the bookmaker.

  3. 3

    Enter the Back Odds

    Enter the decimal odds from the bookmaker. For example, if the odds are 3.00, you'd win $150 from a $50 bet (including your stake back).

  4. 4

    Enter the Lay Odds

    Enter the decimal odds from the betting exchange (e.g. Betfair). These should be as close as possible to the back odds for the best result.

  5. 5

    Check the Commission

    The exchange commission defaults to 5% (Betfair's standard rate). Change this if your exchange charges a different rate.

  6. 6

    Read the Results

    The calculator shows your lay stake, liability, and the net result for both outcomes. For free bets, it also shows the conversion rate.

  7. 7

    Place Your Bets

    Place your back bet at the bookmaker and your lay bet at the exchange using the calculated lay stake. You're covered either way.

The Math Behind Matched Betting

Every matched bet has two sides: a back bet at the bookmaker and a lay bet at the exchange. If you're new to these concepts, our matched betting fundamentals guide walks through each step. The calculator finds the lay stake that balances both sides.

Qualifying Bet Formula

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

This formula minimises your qualifying loss by finding the lay stake that balances both outcomes as closely as possible.

Worked Example

Back Stake$50.00
Back Odds3.00
Lay Odds3.10
Commission5%
Lay Stake$50 × 3.00 ÷ (3.10 − 0.05) = $49.18
Qualifying Loss≈ -$1.64

Free Bet (SNR) Formula

Lay Stake = (Free Bet × (Back Odds − 1)) ÷ (Lay Odds − Commission)

With SNR (Stake Not Returned), you only receive the profit from the back bet, not the stake itself. This is the most common type of free bet.

Worked Example

Free Bet Value$50.00
Back Odds3.50
Lay Odds3.60
Commission5%
Lay Stake$50 × 2.50 ÷ (3.60 − 0.05) = $35.21
Guaranteed Profit≈ $33.45

Free Bet (SR) Formula

Lay Stake = (Free Bet × Back Odds) ÷ (Lay Odds − Commission)

With SR (Stake Returned), you receive both the profit and the stake back. This gives a higher conversion rate. Uses the same formula as the qualifying bet but with no cost if the lay bet wins.

Understanding the Results

Lay Stake

The amount you need to place as a lay bet at the exchange. This is the key number you need to place your lay bet.

Liability

The maximum amount you could lose at the exchange if the back bet wins. This is Lay Stake × (Lay Odds − 1). You need this amount available in your exchange account.

Qualifying Loss

The small loss you accept on a qualifying bet. This is the "cost" of unlocking a free bet offer. Typically $1-3 for a $50 bet.

Guaranteed Profit

The minimum profit you'll make from a free bet, regardless of which outcome occurs. This is real money you keep.

Conversion Rate

The percentage of your free bet value that converts to real cash. For example, a 70% conversion rate on a $50 free bet means ~$35 profit. Higher odds generally give better conversion rates.

When To Use Each Mode

Qualifying Bet

When:

When placing a real bet to unlock a free bet or bonus. See our matched betting concepts guide for a full breakdown.

Goal:

Minimise the qualifying loss.

Example:

"Bet $50 and get a $50 free bet" - the initial $50 bet is the qualifying bet.

Free Bet (SNR)

When:

When using a free bet where only the profit is paid out (most common).

Goal:

Convert the free bet into guaranteed cash.

Example:

"$50 free bet" where a winning $50 bet at 3.00 returns $100 profit (not $150).

Free Bet (SR)

When:

When using a free bet where the stake is also returned with winnings.

Goal:

Convert more of the free bet into cash (higher conversion).

Example:

"$50 bonus bet" where a winning $50 bet at 3.00 returns $150 (profit + stake).

Advanced: Underlay vs Overlay

By default, the calculator balances both outcomes equally. The underlay/overlay slider lets you shift the risk distribution:

Underlay (Negative %)

Reduces your lay stake. You profit more if the back bet wins, but lose more if the lay bet wins. Useful when you believe the back bet has a good chance of winning.

Overlay (Positive %)

Increases your lay stake. You profit more if the lay bet wins, but lose more if the back bet wins. Useful when you want to guarantee more from the exchange side.

For beginners, we recommend leaving this at 0% to keep both outcomes balanced.

Frequently Asked Questions

What is matched betting?
Matched betting is a technique that uses free bets and promotions offered by bookmakers to guarantee a profit. By placing a back bet at a bookmaker and a lay bet at a betting exchange, you cover all outcomes and extract value from the free bet. Our matched betting beginners guide explains the full process step-by-step.
Is matched betting legal in Australia?
Yes, matched betting is completely legal in Australia. You are simply placing bets at bookmakers and exchanges, both of which are licensed and regulated. Gambling winnings are also tax-free in Australia. Learn more in our Australian betting guide.
What does SNR mean?
SNR stands for "Stake Not Returned". When you use an SNR free bet, only the profit is paid out if you win. The free bet stake itself is not returned. This is the most common type of free bet offered by Australian bookmakers.
What does SR mean?
SR stands for "Stake Returned". With an SR free bet, if your bet wins, you receive both the profit AND the original free bet stake back. This results in a higher conversion rate. SR free bets are less common but more valuable.
What is a good conversion rate?
For SNR free bets, a conversion rate of 60-80% is typical. This means a $50 free bet converts to $30-$40 in guaranteed profit. Higher odds generally produce better conversion rates, but also require more liability at the exchange.
What exchange should I use?
In Australia, Betfair is the most popular betting exchange. Their standard commission rate is 5%, which is what this calculator defaults to. Some users may qualify for reduced commission rates over time. Read our complete Betfair Australia guide to get set up.
Why are my lay odds higher than my back odds?
This is normal. Lay odds at the exchange are usually slightly higher than back odds at the bookmaker. The closer the odds are to each other, the smaller your qualifying loss. Try to find events where the difference is minimal.
What is the qualifying loss?
The qualifying loss is the small cost of placing a qualifying bet. For example, if a bookmaker offers "Bet $50, get a $50 free bet", you might lose $1-3 on the qualifying $50 bet, but then make $30-40 profit from the free bet, giving you a net gain of $27-39.
How much money do I need to start?
You can start with as little as $50-100 in your bookmaker account and $100-200 in your Betfair account (to cover liability). As you build profits, you can increase your bet sizes. See our guide on how much money you can make matched betting for realistic expectations.
Can I use this calculator on my phone?
Yes! This calculator is fully mobile-friendly and uses numeric keyboards on mobile devices for easy input. It works on any modern browser.

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