General Motors Co. said its coming Chevrolet Bolt electric car will travel 238 miles on a single charge, giving GM a key marketing claim over Tesla Motors Inc. as the nation’s largest auto maker prepares to begin deliveries of the first long-range, affordable electric vehicle this year.

Ever since GM revealed a concept of the Bolt in early 2015, the Detroit auto maker has said only that its range would top 200 miles on a charge. The estimate of 238 miles disclosed on Tuesday leapfrogs the projected 215-mile range of Tesla’s...