Bonus wagering calculator
A casino advertises the bonus. It does not tell you how much money has to go through the games to release it, or how much of the offer the house edge eats on the way. Put the terms in below and both numbers come out.
Negative. Clearing this bonus costs about £28.00 in house edge to keep £20.00 — on average you end up about £8.00 down by taking it. Playing the deposit on its own costs less.
How the arithmetic works
Nothing here is modelled or simulated. Four lines of arithmetic, printed so you can redo them on paper:
The result is an average, not a promise: variance means any single attempt ends far above or far below it. What the average does tell you is whether the offer is worth taking at all — if the edge cost exceeds the bonus, no amount of luck changes the fact that you are paying for the privilege of clearing it.
Two terms do most of the damage and both are checked in every review we publish: wagering applied to deposit + bonus rather than the bonus alone, and a game contribution below 100%. See how we score bonus terms, or the bonus section for offers with the terms already read and dated.
How to fill this in from a real offer
Every field maps to a line in the operator's bonus terms rather than to the banner, and the two frequently disagree. Open the terms page in another tab and work down.
Deposit is the amount you would actually put in, not the maximum the offer allows. A 100% match up to £200 gives a £20 bonus on a £20 deposit; the £200 is a ceiling, not a gift.
Match rate and max bonus come from the headline: "100% up to £200" is a rate of 100 and a cap of 200. Where an offer is a fixed amount rather than a percentage, set the rate so the two multiply out to the fixed figure.
Wagering and basis are the two that decide most of the answer. Find the multiple, then find what it applies to. "35× the bonus" and "35× deposit and bonus" are the same headline and twice the work, and the second is common enough to check every time.
Game contribution is the weighting for the game you intend to play. Slots are normally 100%, table games often 10% or 20%, live dealer sometimes zero. A game at 10% multiplies your required turnover tenfold, which is why the field is here at all.
RTP is the return-to-player of that game at that casino — the figure in the game's own information panel, not the studio's headline. Many studios ship a title at several settings and the operator chooses; the difference between 96.5% and 92% doubles what clearing a bonus costs.
Max bet is the ceiling on stakes while the bonus is active. It is usually £5, and the calculator uses it to show how many spins the requirement represents. Note that Britain also has a statutory ceiling on online slot stakes — £5 per game cycle for players aged 25 and over since 9 April 2025, and £2 for players aged 18 to 24 since 21 May 2025 — and the stricter of the two governs.
Cash-out cap is the maximum withdrawable from the offer. On a capped offer the cap is the offer, and leaving this field at zero when a cap exists will overstate what the bonus is worth.
The break-even multiple
There is a single number that decides whether a matched offer is worth taking before you calculate anything else, and it falls out of the same arithmetic.
A bonus of B at a multiple of M creates turnover of B × M. At a house edge of E, generating that turnover costs B × M × E on average. The offer breaks even when B × M × E equals B — that is, when M equals one divided by E.
On a 96% slot the edge is 0.04, so the break-even multiple is 25×. Below it, a matched bonus returns more than it costs to clear. Above it, the reverse. On a 94% game the line drops to about 17×; on a 97% game it rises to about 33×.
Most of the British market sits at 30× to 40×, comfortably above the line on any mainstream slot. That is the single most useful fact about casino bonuses, it takes one division to derive, and no operator will ever put it on a promotion.
What the calculator deliberately does not do
It does not predict what you will win. The expected cost is an average over a very large number of stakes, and any single attempt lands somewhere else entirely — often far above or far below. A high-volatility slot can return nothing for an entire clearing attempt and still average 96% across millions of spins.
It does not model the terms that void a bonus rather than price it: a maximum-bet breach, an excluded game, a withdrawal made before the requirement is met. Those are binary rather than arithmetic, and they end the calculation instead of changing it.
It does not account for the game weighting changing mid-clear. If you switch from a slot at 100% contribution to a table game at 10%, the requirement stops moving at a tenth of the rate, and terms frequently prohibit the switch outright while a bonus is active. Set the contribution field to the game you will actually play for the whole attempt rather than to the one you start on.
It does not know whether a bonus is sticky. A sticky bonus can never be withdrawn — only winnings above it become yours — while a non-sticky one converts to withdrawable funds once cleared. The turnover is the same; what you keep at the end is not.
And it does not tell you whether to take the offer. If you were going to stake that turnover anyway, the bonus is a genuine addition to your bankroll and the arithmetic reads differently. If the offer is the reason for the deposit, the honest figure is the one on screen.
Nothing here is advice to gamble. The calculator exists to show what a bonus costs, and the honest answer is usually "more than it looks". Gambling can be addictive — see responsible gambling.