How Lottery Jackpots Grow So Large: How They're Calculated, What Happens When Nobody Wins, and How Often They're Won
When a lottery advertises a $1 billion jackpot, it's easy to picture a vault holding a billion dollars. That's not quite how it works. Jackpots are estimates built from ticket sales, interest rates, and payout rules — and the way they're calculated explains why they can grow so fast.
The Advertised Jackpot Isn't Cash Sitting in a Vault
The big number on the billboard in U.S. games like Powerball and Mega Millions is the annuity value: the total a winner would receive if they chose to be paid in installments over decades.
What the lottery actually holds is a smaller pool of cash. If a winner picks the annuity, that cash is invested so that, over time, it pays out the full advertised amount. If the winner takes the lump sum, they receive the cash value, which is typically a little under half of the advertised figure, depending on interest rates.
We call this gap the headline multiplier: the difference between the cash a jackpot is built on and the larger annuity number used to advertise it.
How a Jackpot Is Calculated
1. Ticket sales fund the prize pool
A portion of each ticket sold goes into prize funds. Part of that funds lower prize tiers, and part goes toward the jackpot.
2. The jackpot has a starting minimum
Each game begins a new jackpot cycle at a guaranteed minimum. Powerball jackpots start at $20 million, and since its April 2025 changes, Mega Millions jackpots start at $50 million.
3. Sales estimates set the next advertised jackpot
Before each draw, the lottery estimates how many tickets will be sold and how much that will add to the jackpot pool.
4. Interest rates convert cash into an annuity value
The lottery calculates how large an annuity the cash pool could fund over the payment period. Powerball and Mega Millions annuities are paid as 30 payments over 29 years, each 5% larger than the last. When interest rates are higher, the same cash pool can fund a larger annuity, so advertised jackpots look bigger.
What Happens When Nobody Wins the Jackpot?
If no ticket matches every number, the jackpot rolls over:
- The jackpot money stays in the pool.
- New ticket sales for the next draw add to it.
- The next advertised jackpot is higher.
Lower prize tiers are still paid in the draw nobody wins. Only the jackpot rolls over.
Some games use different rules:
- Jackpot caps. EuroMillions caps its jackpot at €250 million. When the cap is reached and stays unwon for a limited number of draws, the extra money rolls down to lower prize tiers.
- Must-be-won or rolldown draws. Some lotteries force the jackpot to be paid out to lower tiers after it reaches a certain size or number of rollovers.
Why Rollovers Make Jackpots Explode
Rollovers create a powerful feedback loop:
- Nobody wins → jackpot grows.
- A bigger jackpot attracts more players.
- More tickets sold → jackpot grows faster.
- News coverage attracts even more players.
We call this the jackpot snowball: each rollover makes the next rollover add more money, because a larger jackpot brings in more sales per draw.
Economist Victor Matheson of the College of the Holy Cross, who has studied lottery economics for years, is among the researchers who have examined how strongly ticket sales respond to jackpot size. That responsiveness is exactly what drives the snowball.
How Often Is the Jackpot Won?
The chance that someone wins a jackpot depends on how many different combinations players cover.
Here's a useful piece of math. If players buy tickets with random numbers, and the number of tickets sold equals the number of possible combinations, the chance that at least one ticket wins is about 63% — not 100% — because many tickets duplicate combinations while others go uncovered.
For Powerball, with 292,201,338 combinations:
| Tickets sold for a draw | Approx. chance at least one jackpot winner |
|---|---|
| 10 million | about 3% |
| 50 million | about 16% |
| 150 million | about 40% |
| 292 million | about 63% |
These estimates assume random number selection; real-world patterns, like many players choosing birthdays, change the actual figures.
That's why jackpots can roll over for months when sales are modest, and why they tend to be won once they become huge enough to trigger massive sales.
Why Jackpots Have Grown Over Time
Several changes over the past two decades have pushed jackpots higher:
- Longer odds. Format changes, like Powerball's move to 69 white balls in 2015, made jackpots harder to win.
- Higher prices. Powerball rose to $2 in 2012, and Mega Millions moved to $5 in 2025.
- More participating jurisdictions. Both games are sold across most of the U.S.
- Interest rates. Higher rates increase advertised annuity values.
For the records these changes produced, see The Biggest Lottery Jackpots in History.
Key Takeaways
- Advertised U.S. jackpots are annuity values; the cash in the pool is considerably smaller.
- Powerball jackpots start at $20 million, and Mega Millions jackpots start at $50 million after its 2025 changes.
- When nobody wins, the jackpot rolls over and grows with new ticket sales, while lower-tier prizes are still paid.
- EuroMillions caps its jackpot at €250 million and rolls excess money down to lower tiers.
- Bigger jackpots attract more players, creating a snowball effect that produces record jackpots.
- If as many random tickets are sold as there are combinations, there's still only about a 63% chance of a winner.
Quick Answers
How are lottery jackpots calculated?
Lottery jackpots are estimated from the cash in the jackpot pool plus projected ticket sales for the next draw. In games like Powerball and Mega Millions, that cash is converted into an advertised annuity value based on current interest rates and a 30-payment schedule over 29 years. The lump-sum cash value is smaller.
What happens when nobody wins the lottery jackpot?
When nobody matches all the numbers, the jackpot rolls over to the next draw and grows as new tickets are sold. Lower-tier prizes are still paid. Some games, like EuroMillions, have jackpot caps and roll excess money down to lower prize tiers if the capped jackpot isn't won.
How often does the lottery jackpot get won?
It depends on how many tickets are sold. For Powerball, if around 292 million randomly chosen tickets were sold for one draw, there would be roughly a 63% chance that at least one would win. With fewer tickets sold, jackpots can roll over for many draws, which is how record jackpots build.
Where Jackpots Are Heading
Advertised jackpots are tied to interest rates and ticket prices, both of which have risen in recent years. Our prediction: jackpot sizes will keep climbing, and more games will experiment with caps, rolldowns, and guaranteed secondary prizes to keep players engaged during the long rollover stretches that giant jackpots require.
For the odds themselves, read What Are the Odds of Winning the Lottery?, and for payout choices, see How Lottery Payouts Work: Lump Sum vs. Annuity.