A "stake not returned" free bet is not really worth $50 in cash terms. If you lose, the voucher disappears. If you win, you only receive the profit from the bet, not the original $50 stake.
Laying the same outcome on an exchange gives you another option. Instead of waiting to see whether the free bet wins or loses, you can use the exchange to turn most of its value into a guaranteed amount.
The catch is that you will never get the full $50 back, and there is no fixed percentage that applies to every free bet. The amount you keep depends mainly on the odds you use and the commission charged by the exchange.
The mechanic
Back the free bet at bookmaker odds bo, then lay the same outcome on an exchange at odds lo, with commission c charged on net winnings.
Because the original stake is not returned on a free bet, the back side only pays the profit portion if it wins. That means the payout is stake × (bo − 1), rather than the full stake × bo that you would get from a normal bet.
The lay stake that balances the two outcomes is:
lay stake = stake × (bo − 1) ÷ (lo − c)
Once you have that number, you can calculate the liability and see what remains whichever side wins. That final amount is the real cash value of the free bet.
Worked example
Take a $50 free bet, backed at 4.40 decimal (+340), then lay the same selection at 4.40 on an exchange charging 2% commission:
- Lay stake - $38.81
- Liability - $131.96
- Result if the back bet wins - $38.04
- Result if the lay bet wins - $38.04
$38.04 out of a $50 free bet means you retain just over 76% of its face value.
That percentage is not a general rule. It comes directly from the formula once the odds and commission are fixed.
Why price is the lever
The easiest way to see how much the odds matter is to keep everything else the same and change the price. Here, the back and lay odds are matched exactly and the exchange commission stays at 2%:
- 2.00 - retains 49.5% ($24.75), liability $25.25
- 4.40 - retains 76.1% ($38.04), liability $131.96
- 10.00 - retains 88.4% ($44.19), liability $405.81
- 50.00 - retains 96.1% ($48.04), liability $2,401.96
The jump is biggest at the shorter prices. As the odds get longer, the retention percentage keeps improving, but the improvement becomes smaller and smaller.
The liability tells a different story. Going from 2.00 to 4.40 increases the amount you keep by roughly 1.5 times, but the liability increases by more than five times. Going from 4.40 all the way to 50.00 barely adds anything to the percentage you retain, while the liability increases another 18 times. So chasing very long odds just to get closer to the maximum possible retention quickly becomes expensive.
The ceiling
With very high odds, the retained percentage approaches 1 - c. At 2% commission, that means the theoretical ceiling is 98%.
You can get closer and closer to it, but you can never actually reach it because the exchange still takes its commission.
There is another problem with trying to get as close as possible to that ceiling: liquidity.
Odds of 50.00 or higher are often found in outright markets and more obscure props, where there may not be enough money available on the lay side to match the amount you actually need. Seeing 50.00 on the screen does not necessarily mean you can lay your entire stake at 50.00.
At that point, the problem is no longer the formula. It is whether the market can actually take your bet.
Why lay it at all
It is worth asking what you are actually gaining by laying the free bet instead of simply using it and accepting whatever happens.
Take the same $50 free bet at 4.40. If the price is genuinely fair, meaning the market's implied probability is actually correct, the expected value of simply placing the free bet is:
p × (bo - 1) × stake = (1 ÷ 4.40) × 3.40 × $50 = $38.64
That is slightly higher than the $38.04 you lock in by laying it.
The difference, around 60 cents, is essentially the price of removing the uncertainty. If you simply use the free bet, there is a 22.7% chance of receiving $170 and a 77.3% chance of receiving nothing.
By laying it off, you turn that uncertain result into a guaranteed $38.04.
So laying does not magically create extra value. You are giving up a small amount of expected value in exchange for removing almost all of the variance.
Whether that is worthwhile depends on what you prefer: a guaranteed amount now, or a larger amount that only arrives if the bet wins.
Where laying becomes much more useful is when you have several free bets. One free bet used normally can go either way. Ten free bets laid off individually give you a much more predictable combined result because the uncertainty has been removed from each one.
That is one of the main reasons matched betting works as a repeatable process. You are not relying on a free bet winning and hoping the results balance themselves out later. You are converting each offer into a relatively predictable amount.
The liability has to actually be sitting there
The retention figures above only work if you can actually fund the exchange liability.
At 4.40, that means having $131.96 available on the exchange when you place the lay. That is more than 2.6 times the $50 face value of the free bet.
At 10.00, the liability is $405.81.
At 50.00, it is $2,401.96.
This is important if you are handling several offers at once. The amount of money needed to cover the liabilities can become the real limitation long before commission becomes the main concern.
Free bet terms that change the formula
- Minimum qualifying odds. Many bookmakers only honour the free bet if it is placed at or above a minimum price - commonly around 1.50 to 2.00 decimal. That sets a floor on bo, not a ceiling; the long-price strategy above is normally unaffected, but a bet placed below the minimum can void the free bet entirely.
- Rollover or wagering requirements. Some "bonus" offers are not free bets at all in the sense used here - they require the bonus amount to be wagered multiple times before any of it can be withdrawn. The formula in this article applies to a genuine free bet, credited once and usable once; it does not apply to a rollover bonus, which needs a different framework entirely and is usually not worth laying off in the same way.
Stake returned is a different calculation
Some promotions return the original stake as well as the profit when the bet wins. That is a "stake returned" free bet, and it works differently from the type discussed here.
A stake-returned bonus pays stake × bo rather than stake × (bo − 1), so you would use the normal back/lay calculation instead.
It is worth checking the exact terms before doing the maths. Using the free-bet formula on a stake-returned offer will under-hedge it, while using the normal stake-returned formula on a genuine stake-not-returned free bet will over-hedge it.
What actually moves the number
- Back and lay odds close together. The formula assumes they match exactly. Any gap - the bookmaker offering worse value than the exchange, or vice versa - pulls the two outcomes apart and lowers whichever one ends up guaranteed.
- Commission rate. Moving from 2% to 5% commission on the same 4.40 free bet drops the guaranteed result from $38.04 to $37.13. A smaller effect than price, but never zero, and worth checking before you commit to an exchange.
- Odds format. Free bets are usually quoted at whatever price the bookmaker displays, which is not always decimal. Convert first, calculate second.
The safest approach is to run the actual numbers through the free bet value calculator before placing anything. The odds you can genuinely get, rather than the odds in an example, are what determine how much your free bet is worth.
And if you are considering a particularly long price, check the exchange ladder as well. A price being displayed does not necessarily mean there is enough money available to match the entire lay at that price.