Bonus ball, in full
In the same-pool version, one extra ball comes out of the same drum after the main numbers. UK Lotto draws a seventh ball from the 59, and Irish Lotto draws its bonus from the balls still left in the drum. Players never choose it. Its only job is to split one match level into two, so a ticket matching five main numbers lands in a higher tier if its sixth number happens to be the bonus.
The separate-pool version works differently. Powerball's red ball is drawn from its own set of 26, the Mega Ball from a set of 24, and EuroMillions draws two Lucky Stars from 12. Players pick these themselves, and matching them is part of the jackpot condition rather than a tie-break. A Powerball jackpot needs five white balls and the red one, which is why the odds are 1 in 292,201,338 and not 1 in 11,238,513.
Mixing the two up leads to a common error. A same-pool bonus ball cannot make the jackpot harder to reach, because the jackpot is decided before it drops. A second-pool ball multiplies the size of the whole outcome space. The clue is in whether the ticket asks you to pick the extra number: if you pick it, it is a second pool, and if you do not, it only sorts the lower tiers.
- Lottery mechanics
- Supplementary ball, Bonus number
A worked example
One round of UK Lotto draws 6 from 59, giving 45,057,474 tickets. To match five plus the bonus, five of your six numbers must be main numbers and the sixth must be the bonus ball, which happens in 6 of those combinations, so 1 in 7,509,579 for that round. Matching five without the bonus happens in 6 × 52 = 312 combinations, or about 1 in 144,415. Since June 2026 a line plays two rounds a night, each with its own bonus ball, so the published per-line figures are roughly half those counts.
Sources
The Powerball jackpot, which needs the five white balls and the red Powerball, is quoted at odds of 1 in 292,201,338.
Powerball — Prize ChartThe Mega Ball is chosen by the player from a separate pool of 24 numbers.
Mega Millions — FAQsEuroMillions takes five main numbers from 50 and two Lucky Stars from a pool of 12, and the jackpot needs all seven.
Wikipedia — EuroMillionsUK Lotto draws six balls from 59, then a further Bonus Ball from the same set, which affects only players matching five main numbers.
Wikipedia — National Lottery (United Kingdom)
See also
Where it comes up on this site
Bonus ball: frequently asked
Depends on the game. UK Lotto and Irish Lotto take the bonus from the same drum as the main numbers, so nobody chooses it. Powerball, Mega Millions and EuroMillions ask you to pick the extra number yourself, and that one comes from a separate pool.
Only when it comes from a second pool. A same-pool bonus drops after the jackpot has already been decided, so it cannot make the top prize harder to reach. All it does is split one match level in two. A second-pool ball is part of the winning combination, and that is a different kind of change. Powerball's red ball multiplies the white-ball count of 11,238,513 by 26, which is how the jackpot odds arrive at 1 in 292,201,338.