Wagering calculator: what a bonus really asks you to stake
Type in the numbers from a bonus clause. The calculator turns them into the total you must stake, the number of bets that takes at the minimum odds, and what that staking costs on average.
Illustrative example
- Wagering base
- KES 1,000
- Total turnover required
- KES 5,000
- Bets at the minimum odds
- 5 bets of KES 1,000 at odds of 1.50 or higher
- Expected cost of that turnover
- KES 250 at a 5% margin
- Bonus left after the expected cost
- KES 750
To make KES 1,000 withdrawable you must stake KES 5,000 in total, at odds of 1.50 or higher. At a 5% margin that staking costs about KES 250 on average, so the bonus is worth about KES 750 before tax.
Averages over many bets, before tax. One real bet can land anywhere. Figures are illustrative and come from the inputs, not from any operator.
How the figures are worked out
The calculator uses five lines of arithmetic, in this order. Nothing is fetched from an operator; every figure comes from what you type.
| Output | How it is worked out |
|---|---|
| Wagering base | The bonus, plus the deposit if the terms include it |
| Total turnover required | Base x rollover multiplier |
| Bets at the minimum odds | Turnover ÷ bonus amount, rounded up, with each bet staked at the bonus amount |
| Expected cost | Turnover x margin |
| Bonus left | Bonus minus the expected cost |
The fourth line is the one headlines leave out: every shilling of turnover pays the margin, whether the bet wins or loses. That is how a large rollover can cost more than the bonus is worth.
Where the 5% margin comes from
A bookmaker's margin is built into the odds. Each decimal price implies a probability of 1 ÷ odds. On a book with no margin the implied probabilities of all outcomes would add up to 100%; in practice they add up to more, and the excess is called the overround.
Illustrative example. A two-way market priced 1.90 and 1.90 implies 52.63% for each side, 105.26% in total: an overround of 5.26%. If each side really has a 50% chance, a KES 100 bet at 1.90 returns KES 190 half the time, or KES 95 on average. The book keeps KES 5 of every KES 100 staked, which is the 5% the calculator starts with.
Bonus alone, or deposit plus bonus
Two clauses can look alike and ask for very different amounts. "The bonus must be wagered 5 times" and "the deposit and bonus must be wagered 5 times" differ by the size of your deposit, multiplied by five.
| What the clause wagers | Base | Turnover | Bets of KES 1,000 | Expected cost | Bonus left |
|---|---|---|---|---|---|
| Bonus only | KES 1,000 | KES 5,000 | 5 | KES 250 | KES 750 |
| Deposit and bonus | KES 2,000 | KES 10,000 | 10 | KES 500 | KES 500 |
In a 100% match, including the deposit doubles both the turnover and the cost. The guide to a deposit match bonus, worked in shillings sets out the full arithmetic of a matched offer.
When the rollover uses up the bonus
At a fixed margin the expected cost grows in step with the rollover. At 5%, the cost equals the bonus when the rollover reaches 1 ÷ 0.05, which is 20 times the bonus.
| Rollover | Turnover | Expected cost | Bonus left on average |
|---|---|---|---|
| 1x | KES 1,000 | KES 50 | KES 950 |
| 5x | KES 5,000 | KES 250 | KES 750 |
| 10x | KES 10,000 | KES 500 | KES 500 |
| 20x | KES 20,000 | KES 1,000 | KES 0 |
| 30x | KES 30,000 | KES 1,500 | Minus KES 500 |
Past that point the offer costs more on average than it gives. A deposit-plus-bonus base in a 100% match gets there twice as fast, at 10 times. The guide to wagering requirements shows, with more examples, how the margin makes turnover expensive.
What the minimum odds change
The minimum odds do not change the turnover: KES 5,000 is KES 5,000 whether it is staked at 1.50 or at 3.00. They decide which bets count and how often each one loses.
| Decimal odds | Implied chance of winning |
|---|---|
| 1.50 | 66.7% |
| 2.00 | 50% |
| 3.75 | 26.7% |
An accumulator multiplies its legs: four legs at 1.50 give combined odds of 5.06 and an implied chance of 19.75%. Combining short prices to pass a minimum-odds rule makes each qualifying bet far less likely to win. The guide to the minimum odds rule covers how terms treat accumulators.
What the calculator leaves out
- Running out of balance. The averages assume you finish the turnover. A run of losing bets can empty the bonus balance first, and the attempt ends with nothing to withdraw.
- The clock. An expiry clause sets how long you have. Fitting the turnover into that time can mean larger or more frequent bets than you planned. See expiry and maximum win clauses.
- Maximum win. A cap on withdrawable bonus winnings limits what you can take out, not what the turnover costs.
- Tax. The resident withholding rate on withdrawals made by punters is 5% (Income Tax Act, Third Schedule, Head B, paragraph 5(i)), deducted by the payer under section 35. Excise duty of 5% is charged on the amount deposited for betting (Excise Duty Act, First Schedule, Part II, paragraph 4A, as amended by section 36 of the Finance Act, 2026). The guide to tax on winnings from a free bet or bonus works through both.
What the law says about bonus offers
Section 74(1)(b) of the Gambling Control Act, 2025 bars a licensee from making an offer designed to induce people to take part in gambling or to increase their participation. Section 74(3) adds that this does not limit free bets and bonus bets offered in the ordinary course of business, and the proviso to section 72(7) says the same about the ban on advancing credit to a player.
Rule 23 of the Conduct of Gambling Operations Regulations, 2026 (L.N. 112) requires a licensee to display the odds, rules and terms of each bet clearly and bars it from changing a bet's terms once the bet is accepted. Read the terms before the first qualifying bet: the calculator is only as good as the numbers you copy from them. When a bonus is withdrawn after the fact, the guide on whether a bookmaker can cancel a bonus sets out the complaint route.
Questions readers ask
Does the calculator use a real operator's offer?
No. The starting figures, a KES 1,000 bonus with a 5x rollover, minimum odds of 1.50 and a 5% margin, are an illustrative example written for this site. Replace them with the numbers in the terms you are reading.
Why do the minimum odds not change the number of bets?
The requirement is counted in shillings staked, not in bets won. Five bets of KES 1,000 meet a KES 5,000 requirement at any qualifying price. Higher odds change how likely each bet is to win and how quickly the balance can run out, which the calculator does not model.
Is the expected cost what I will lose?
Not exactly. It is the average loss over a very large number of bets at that margin. Any one set of bets can end well above or well below it, and a losing run can end the attempt before the turnover is complete.
Does the calculator send my numbers anywhere?
No. The arithmetic runs in your browser, and the page has no form that submits to a server. The privacy page lists what the site does and does not record.