Ellen makes billionaire Bill Gates guess everyday grocery prices. He’s really bad at it.

Don't expect one of the world's richest men to know how much a bag of grocery store pizza rolls costs — because he obviously has no idea.

Billionaire Bill Gates was Ellen DeGeneres' guest Wednesday on "The Ellen DeGeneres Show," and during the episode, Gates and DeGeneres played a little game called "Bill's Grocery Bills."

DeGeneres told Gates and the studio audience that if the Microsoft mogul was able to correctly guess the prices of certain grocery store products within just a dollar, the audience would win a prize.

After the show host asked Gates how long it had been since he'd stepped foot inside a grocery store, Gates quipped, "Long time ago."

DeGeneres kicked off the game by asking how much Gates believed a box of Rice-A-Roni went for nowadays. Though the answer was $1, Gates answered $5.

She continued and asked Gates the price of dental floss, and luckily, this time he was much closer — and within a dollar.

But a bag of Totino's pizza rolls? Gates guessed $22. The actual price was $8.98.

The audience collectively groaned in a good-natured way.

For what Gates is worth, he can purchase approximately 10,188,888,888 sacks of pizza rolls — which is an awful lot of pizza.

Gates, only with DeGeneres' promptings and suggestions from the audience, scraped by and won the game.

The audience members were gifted with return visits to "The Ellen DeGeneres Show" to take part in her annual 12 Days of Giveaways event.

See the hilarious segment below.