What Is a Matched Betting Calculator?
A matched betting calculator works out exactly how much to lay on a betting exchange to cancel out a bet you have placed with a bookmaker. By backing an outcome with a bookmaker and laying the same outcome on an exchange, you cover every result and lock in a known position — turning free bets and bookmaker promotions into low-risk profit. Note: matched betting laws and the availability of betting exchanges vary by country; this tool is a neutral mathematical aid and not betting advice.
How to Use It
Enter the bookmaker's back odds (decimal), your back stake, the exchange's lay odds, and the exchange commission as a percentage. The calculator returns the optimal lay stake, the liability you must cover on the exchange, and your guaranteed profit or qualifying loss whichever side wins.
The Formula Explained
The lay stake is chosen so both outcomes return the same net amount: $$\text{Lay Stake} = \frac{\text{Back Odds} \times \text{Back Stake}}{\text{Lay Odds} - \dfrac{\text{Commission \%}}{100}}$$ where commission is a decimal. Profit is $$\text{Profit} = \text{Back Stake}\left(\text{Back Odds} - 1\right) - \text{Lay Stake}\left(\text{Lay Odds} - 1\right)$$ A positive figure is locked-in profit; a small negative figure is a qualifying loss you accept to unlock a free bet.
Worked Example
Back odds 2.5, back stake £100, lay odds 2.6, commission 5% (0.05). $$\text{Lay Stake} = \frac{2.5 \times 100}{2.6 - 0.05} = \frac{250}{2.55} = £98.04$$ $$\text{Liability} = 98.04 \times 1.6 = £156.86$$ $$\text{Profit} = 100 \times 1.5 - 98.04 \times 1.6 = 150 - 156.86 = -£6.86$$ — a typical qualifying loss for a normal (non-free) bet.
FAQ
Why is the profit sometimes negative? On a qualifying bet you usually accept a tiny loss; the real profit comes when you use the free bet the promotion unlocks.
What are decimal odds? Decimal odds include your stake, so odds of \(2.5\) return £2.50 per £1 staked (£1.50 profit).
Does commission apply to the back bet? No — exchange commission only applies to net winnings on the lay side, which is why it is subtracted from the lay odds.
