This article explains how to calculate matched bets, to give you a clear understanding of the maths behind matched betting, and why it’s a low-risk betting strategy. Learn how to calculate qualifying bets, free bet stake returned and free bet stake not returned matched bets.
We have already explained in detail what matched betting is, but for the basis of this article, it is simply converting a bookmaker’s free bet or bonus into real money.
To do this you must place a back bet with the bookmaker who offered you the bonus and then lay - read what lay betting is on an exchange - the same result on the Smarkets betting exchange - allowing you to cover all potential outcomes, removing your risk, and lock in a profit regardless of the result.
You complete matched bets in two stages:
- Qualifying bet
- Free bet stake returned/stake not returned
Below we explain how to calculate these matched betting bets, and calculate your return. For the examples, we will use a hypothetical bonus of “Bet £20, get a £20 free bet”.
How to calculate a qualifying matched bet
All matched bets require you to make a qualifying bet, which ensures you are eligible to receive the bookmaker bonus.
We know to qualify for this matched bet we must bet £20 to receive a £20 free bet. You have decided to back Ipswich Town to beat Derby County with the bookmaker at odds of 1.58 and laid them on the Smarkets exchange - industry-low 2% commission - for 1.60.
1: Calculate optimal lay stake:
Once you have made your back bet you need to calculate your optimal lay stake with the equation below:
Qualifying bet optimal lay stake = back odds / (lay odds – exchange commission) * back stake
So for our example, that would be:
You would then make a £20 lay bet on Ipswich to win at odds of 1.60.
2: Calculate profit if the back bet wins:
Now you have placed your two bets - one with the bookmaker and one with the exchange - you can calculate your profit if the bet with the bookmaker wins.
Profit = (back odds – 1) * back stake – (lay odds -1) * lay stake
So for our example, that would be:
3: Calculate profit if the lay bet wins.
To calculate your profit if your lay bet with the exchange is successful use this equation:
Profit = lay stake * (1 - commission) - back stake
In our example that would be:
4: Qualifying bet profit
The table below shows all outcomes and your profit for your qualifying bet - this includes the 2% commission charged on the exchange if your bet won.
Outcome |
Bookmaker |
Smarkets exchange |
Profit/loss |
Ipswich win |
+ £11.60 |
- £12.00 |
- £0.40 |
Ipswich don’t win |
- £20.00 |
+ 19.60 |
- £0.40 |
So if you placed this qualifying bet, you would lose £0.40. However, you will receive your free £20 bet.
How to calculate a free bet stake not returned (SNR) matched bet
Once you have qualified for your free bet, you will have received your bookmaker bonus. The process is very similar to above, but the equations are slightly different - because the back bet is placed using the bookmaker’s free bet.
Find similar back and lay priced odds like before. For this example let’s say you have placed £20 on the horse Talaayeb at 4.1 with the bookmaker on the 15:05 at Newbury and laid him for 4.2 on the Smarkets exchange.
1: Calculate optimal lay stake:
Once you have made your back bet you need to calculate your optimal lay stake using the equation below:
SNR optimal lay stake = (back odds – 1) / (lay odds – commission) * back stake
So for our example, that would be:
You would then make a £14.83 lay bet on Talaayeb to win at odds of 4.2 on the betting exchange.
2: Calculate profit if the back bet wins:
Now you have placed your two bets - one with the bookmaker and one with the exchange - you can calculate your profit if the bet with the bookmaker wins the same as before:
Profit = (back odds – 1) * back stake – (lay odds -1) * lay stake
So for our example, that would be:
3: Calculate profit if the lay bet wins:
Next, you calculate your profit if your lay bet with the exchange is successful - here we don’t account for the loss of the back stake, as it’s the bookmakers own money (bonus they offered).
Profit = lay stake * (1 - commission)
So for our example that would be:
4: Free bet stake not returned (SNR) profit
The table below shows all outcomes and your profit for your free bet SNR matched bet - this includes the 2% commission charged on the exchange if your bet won.
Outcome |
Bookmaker |
Smarkets exchange |
Profit/loss |
Talaayeb wins |
+ £62.00 |
- £47.45 |
+ £14.55 |
Talaayeb doesn't win |
£0.00 |
+ £14.53 |
+ £14.53 |
So if you placed this free bet SNR matched bet, you would win £14.53 of the original £20 free bet.
How to calculate a free bet stake returned (SR) matched bet
The bookmaker may offer you a free bet which includes returning the free bet with your winnings. Like before you can calculate the lay bet to extract an equal profit.
As an example let’s say the original qualifying bet gave you a £20 stake returned free bet. So you've placed £20 with the bookmaker on Andy Murray at 6.00 to beat Novak Djokovic and laid him for 6.2 on the Smarkets exchange.
1: Calculate optimal lay:
Once you have made your back bet you need to calculate your optimal lay stake using the equation below:
SR optimal lay stake = back odds / (lay odds – commission) * back stake
So for our example, that would be:
You would then lay Andy Murray for £19.42 to win at odds of 6.20 on the betting exchange.
2: Calculate profit if the back bet wins:
Now you have placed your two bets you can calculate your profit if the bet with the bookmaker wins - this time we don’t minus ‘1’ from the back odds:
Profit = back odds * back stake – (lay odds -1) * lay stake
So for our example, that would be:
3: Calculate profit if the lay bet wins:
You then calculate your profit if your lay bet with the exchange is successful:
Profit = lay stake * (1 - commission)
So for our example, that would be:
4: Free bet stake returned (SR) profit
The table below shows all outcomes and your profit for your free bet SR matched bet - this includes the 2% commission charged on the exchange if your bet won.
Outcome |
Bookmaker |
Smarkets exchange |
Profit/loss |
Murray wins |
+ £120.00 |
- £100.98 |
+ £19.02 |
Murray doesn't win |
£0.00 |
+ £19.03 |
+ £19.03 |
So if you placed this free bet SR matched bet, you would win £19.02 of the original £20 free bet.
Apply this to betting
Now you understand how to calculate matched betting bets, and the maths behind them, you can see why it’s a low-risk betting strategy - low-risk not risk-free because of the potential for human error.
Remember the key to matched betting is to draw as much profit from the original free bet, to do this you should use an exchange which offers you the best commission structure - which is what Smarkets does with an industry-leading fixed 2% commission structure on net market wins only.