Bill Gates has no idea what groceries cost, but you should - here's how much it costs to buy groceries in 25 major US cities

• Bill Gates, the second richest person in the world, recently appeared on an episode of "The Ellen DeGeneres Show."
• Ellen DeGeneres quizzed Gates on his knowledge of grocery prices, and he failed miserably at guessing the cost of laundry detergent and other staples.
• The cost of groceries varies depending on where you live - we put together a list of the average cost of food staples in 25 major cities across the US.

Bill Gates has no idea what groceries cost.

During an appearance on a recent episode of "The Ellen DeGeneres Show," the world's second richest person couldn't correctly guess the price of Tide Pods or Rice-a-Roni.

But for most people, it's pretty important to know exactly what your bank account is in for when hitting the supermarket.

According to a 2017 survey by Gallup, the weekly median spending on food for American families is $130 - that's roughly $520 a month. Specifically, 24% spend less than $100 a week, 42% spend $100 to $199 a week, 18% spend $200 to $299 a week, and 12% spend $300 or more.

But that amount of money could go a little or a long way depending on where you live. Groceries are notoriously more expensive in certain cities (looking at you, New York and San Francisco).

From Atlanta to Los Angeles to Gates' hometown of Seattle, we took a look at how much groceries cost in 25 major US cities. We used NerdWallet's cost of living calculator to get a better picture of just how much money three basic food staples - bread, a dozen eggs, and a gallon of milk - will take out of your grocery budget.

Maybe Bill could learn a thing or two.