A lottery is a game in which people buy numbered tickets. The numbers are then drawn at random, and the people who have those numbers on their tickets win a prize. Lotteries are a popular source of public funding for things like schools, hospitals, roads and canals. They are also used to award sports team rosters, university placements and more.

Despite the fact that they know their odds are long, many people still play the lottery. Some do it for fun, and some do it out of a sense that winning the lottery may be their last, best or only chance at getting rich. These people go into the game clear-eyed about the odds and what they’re up against. They’ll often choose their lucky numbers, stick to the same store and time of day they purchase tickets, or even use a quote-unquote system that isn’t based in statistical reasoning.

But what if there was a way to win the lottery without buying a ticket? That’s what mathematician Stefan Mandel did, and he shared his formula with the world.

Essentially, you take the total amount of money that has been paid into the pool for a lottery draw and divide it by the number of tickets sold. The remainder of that sum is the prize amount. Then, you subtract the costs and profits for organizing and promoting the lottery and, if applicable, the percentage that goes to taxes and fees, leaving the net prize.