Matched betting
Free bet calculator — stake not returned
Almost every free bet a bookmaker issues is stake-not-returned: if the selection wins you are paid the winnings only, and the token itself is consumed. A EUR 20 free bet at 6.00 therefore credits EUR 100, not EUR 120. This calculator sizes the exchange lay that leaves the same figure on the table whichever way the event goes, and reports that figure as a percentage of the token face value — the number the industry calls retention.
Retention is what the free bet is actually worth to you, and it is always less than the face value, because the part of the return you never receive is the stake. How much less depends on three things the calculator makes explicit: the back price, the gap between the back and lay prices, and the commission the exchange charges on the lay. It reports the worse of the two outcomes rather than the better one, so the figure shown is the one available on both results rather than the flattering leg.
Inputs
The face value printed on the token. Only the winnings are paid out — this amount is not.
Longer prices generally give a higher retention percentage, provided the exchange price stays close.
The gap between the back and lay price is the spread. A wider spread lowers retention.
Charged on the net winnings of the lay bet. Typically 2%, but varies by exchange and by market.
Result
- RetentionWorst-case return as a percentage of the €10.00 face value
- 79.30%
- Worst-case returnThe lower of the two outcomes below — the amount the position leaves on either result
- €7.93
- Lay stake
- €8.09
- Liability at the exchangeMoney that must be available in the exchange account before the lay is placed
- €42.07
- If the bookmaker selection winsFree bet winnings, less the exchange liability
- €7.93
- If the exchange selection winsLay stake net of commission. The free bet itself cost nothing, so nothing is lost on that side
- €7.93
This is the arithmetic of the prices entered, assuming both legs are matched in full at exactly those prices. Exchange liquidity at long prices, movement between placing the two legs, minimum-odds or minimum-stake terms attached to the token, a void event, and account restrictions all change the real outcome.
How this is calculated
lay stake = (F x (B - 1)) / (L - c) retention = worst-case return / F
F is the face value of the free bet, B the back price, L the lay price and c the commission rate as a fraction. The numerator is F x (B - 1) rather than F x B because a stake-not-returned token pays the winnings only: a EUR 20 free bet at 6.00 credits EUR 100, not EUR 120. The denominator is L - c because exchange commission is charged on the lay bet's net winnings, which reduces the effective lay price by exactly c. To check a result by hand, take the lay stake and do two things with it: multiply by (L - 1) to get the liability, then subtract that liability from F x (B - 1) to get the position when the bookmaker selection wins; separately, multiply the lay stake by (1 - c) to get the position when the exchange selection wins. Those two figures should agree to within a cent or so of rounding. Retention is that figure divided by F. Note the ceiling this implies: even with zero commission and an identical back and lay price, retention works out at (B - 1) / B — 50% at 2.00, 83.33% at 6.00, 95% at 20.00. It therefore rises towards 100% as the back price lengthens without ever reaching it, and any spread or commission pulls it below that line.
Worked example
A EUR 20 stake-not-returned free bet placed at 6.00 with the bookmaker and laid at an exchange showing 6.20, with 2% commission.
- 01The token has a face value of EUR 20, but at 6.00 it credits winnings only: 20 x (6.00 - 1) = EUR 100.
- 02Commission of 2% is 0.02 as a fraction, so the equalising denominator is 6.20 - 0.02 = 6.18.
- 03Lay stake = 100 / 6.18 = EUR 16.18.
- 04Liability = 16.18 x (6.20 - 1) = EUR 84.136, rounded up to EUR 84.14 because it is money that has to be sitting in the exchange account.
- 05If the selection wins: EUR 100 credited by the bookmaker, less the EUR 84.14 liability = EUR 15.86.
- 06If the selection loses: the lay stake of EUR 16.18 less 2% commission = EUR 15.86 after rounding, and the free bet itself cost nothing.
- 07Both results land on EUR 15.86, which is 79.30% of the EUR 20 face value — the retention figure for these three inputs.
Questions
Why is a EUR 20 free bet not worth EUR 20?
Because the stake is not returned. The bookmaker pays the winnings and keeps the token, so at 6.00 a EUR 20 free bet produces EUR 100 rather than EUR 120 — the missing EUR 20 is the stake you never had. Laying the selection converts that one-sided return into the same figure on both results, but it cannot conjure back the part the bookmaker never pays. That is why retention is quoted as a percentage of face value rather than the face value itself.
Why does retention change so much with the back price?
The stake you forfeit is a fixed amount, but the return grows with the price, so at longer odds the forfeited stake is a smaller share of the whole. At an identical back and lay price with no commission the arithmetic gives exactly (B - 1) / B: 50% at 2.00, 75% at 4.00, 90% at 10.00. Spread and commission then subtract from that. Long prices also carry a practical cost the percentage does not show — the liability is far larger, and exchange liquidity is usually thinner.
Why might the real result differ from the figure shown?
Several ways, and they mostly reduce it. The lay may be only partly matched, or matched at a longer price than quoted if the market moves between placing the two legs — at long odds a couple of ticks moves the figure noticeably. The token may carry minimum-odds or minimum-stake terms that force a worse price. If the event is void the bookmaker may not re-credit the free bet while the exchange simply cancels, leaving nothing. Some markets are charged a different commission rate than the account default. Bookmakers also restrict or close accounts that use promotions this way, which ends the exercise regardless of the arithmetic.
How much money do I need in the exchange account?
The liability figure, which is much larger than the free bet itself — a EUR 20 free bet at around 6.00 needs roughly EUR 84 of liability available. It is rounded up rather than to nearest, because rounding it down would tell you that you need less than you do and the lay would be rejected. The liability is returned to you if the selection loses; it is paid out if the selection wins, which is the side where the bookmaker credits you instead.
Related calculators
These calculators are information tools. They describe the arithmetic of the prices you enter — they are not advice, and they do not predict outcomes. Betting involves risk. 18+ only. If gambling is causing you harm, support is available from Peluuri.