"We believe this is the right leadership role ... to be providing more information so consumers can make better-informed purchase decisions about the food they eat," Yum spokesman Jonathan Blum said.
Yum said its calorie counts will be based on individual serving sizes rather than, for instance, on an entire pizza or bucket of chicken that a family would dig into.
Yum said it will encourage its franchisees to provide the same calorie information on their menu boards.
"We're hopeful that it will be at all of our restaurants across the United States," Blum said.
Louisville-based Yum has about 20,000 U.S. restaurants, and about 4,000 are company-owned.
The company said the calorie information will be phased onto menu boards starting this year and completed by Jan. 1, 2011. "We'll begin as quickly as we can," Blum said.
The decision comes as public policies requiring restaurant chains to post nutritional information are gaining a foothold. California Gov. Arnold Schwarzenegger signed legislation Tuesday requiring chains with at least 20 restaurants in the state to provide calorie counts on menus or indoor menu boards beginning in 2011. New York City also requires chains to post calorie counts on the menu.
Yum's decision got a thumbs-up from a consumer watchdog group.
Michael Jacobson, executive director of the Center for Science in the Public Interest, called it a groundbreaking announcement that is "fabulous news for health-conscious consumers."
"We applaud this move and encourage other major chains to follow this bold example," Jacobson said.
Jacobson added: "I never thought I'd say this, but I salute Colonel Sanders" - referring the founder of Kentucky Fried Chicken.
Asked if McDonald's Corp. plans to post calorie information on its menu boards nationwide, spokesman Walt Riker said the fast-food giant will continue using current methods of informing customers.
McDonald's said it provides nutritional information on its Web site, on select product packaging, in brochures available in its restaurants and on the back of trayliners.
"Customers are telling us that they are satisfied with the information we're providing," Riker said.
Yum said the calorie counts will be posted on menu boards inside its stores. Drive-through customers can request nutritional brochures already available in stores.
Asked if the company anticipated a shift in sales away from higher-calorie items, Blum said, "All food can be part of a balanced diet if eaten in moderation and balanced with exercise."
Each of Yum's restaurant brands already offer lower calorie menu options.
Yum said it will push for federal legislation to set uniform guidelines for such calorie displays.
"We think every supermarket, restaurant, convenience store - anybody who sells prepared food - ought to follow one standard, uniform guideline," Blum said.
Yum also announced it will quit advertising its products on television programs aimed at children under 12. Blum said the company does little advertising on such programs, but said "we're taking a stand."
The company said it will launch national online exercise programs featuring University of Louisville men's basketball coach Rick Pitino to help educate consumers about maintaining a balanced lifestyle.
The moves are the company's latest efforts to keep up with health conscious customers. In 2007, Taco Bell and KFC switched to cooking oils with zero grams trans fat per serving.
Shares of Yum Brands fell 20 cents to $32.41 in morning trading Wednesday.