The colloquial phrase "dollars to donuts", sometimes spelled "dollars to doughnuts" or used with other monetary units, indicates that something is exceedingly likely to happen. When placing a bet, the person gambling feels that their outcome is a sure thing. They feel so confident that they believe they could gamble their dollars against someone else's donuts, indicating that even though the bet is lopsided the gambler thinks there is no way they can lose and they'll end up with a box of free donuts.
Of course, many gamblers feel like they're going to win, which is why gambling exists. Sometimes this slang phrase is used to psyche themselves up to place the bet. The unfortunate problem is that sometimes the donuts win.
- Buster Douglas versus Mike Tyson (1990): Most gambling houses would not take any bets on this fight because the world believed Mike Tyson would knock out the overweight and past his prime Douglas.
- Ronda Rousey versus Holly Holm (2015): Rousey entered the ring undefeated and with a string of knockouts mere minutes into her UFC fights. Holm landed a kick to Rousey's head in the second round that took the champion out.
- The Olympics "Miracle on Ice" - USA versus USSR (1980): The Russians had stocked their team with NHL-class players, but they ended up losing to a United States team that had a lot of heart.
Those that had a few bucks on the underdogs made a killing and were able to buy all of the donuts they could want. As they say, there's no such thing as a sure thing.