*To compare items of different quantities, unit price was used to calculate total cost.

WINNER: Walmart

To find out whether Kroger, Walmart, or Aldi is the cheapest grocery store, we checked prices on the same items, but not necessarily the same brands, at three stores in the same western Ohio market area.

We filled our shopping cart with several products from each department, including milk, a dozen eggs, and butter from the dairy case; chicken breast and ground beef from the meat counter; enough produce to make a decent salad; condiments such as ketchup, ranch dressing, and peanut butter; frozen foods such as pizza and family-size lasagna; bread and buns from the baked goods aisle; and staples such as pasta, flour, chicken broth, soda, juice, and cereal.

Photo credit: Chris Hondros/Getty Images

To make our grocery store price comparison fair, we calculated a per-unit price for like items of unequal amounts or sizes, and then used that result to determine the total cost for the most commonly sold quantity. For example, russet potatoes were available at both Aldi and Walmart in 10-pound bags but Kroger was selling 8-pound bags, so we projected the cost of a 10-pound bag at Kroger using the price per pound.

Our final tally produced a clear overall winner: Aldi, where the grocery bill came to $67.34, about 14% cheaper than the Walmart total of $78.23 and more than 20% cheaper than Kroger (even with a store savings card). Aldi outpriced Walmart on 33 of 41 items. Kroger was never the cheapest choice.

However, more than 90% of the products at Aldi are private label, and the discount grocer carries few national or regional brands. For shoppers who prefer not to buy generic equivalents of their favorite brands, we also did a Walmart vs. Kroger price comparison of popular name-brand products. When we compared prices on 30 national brands — products like Jif peanut butter, Uncle Ben's rice, and Dannon yogurt — Walmart was the cheapest grocery store, with overall savings of 9% over Kroger Plus Card prices and double that without a savings card. Only five items in our shopping cart were less expensive at Kroger than at Walmart, and three of those were cheaper only for Kroger Plus Card holders.