Cameron revealed he had a Panasonic breadmaker, which typically costs more than £100, and liked to use Cotswold Crunch flour, which is on sale online for £30.20 for a 16kg bag.
He stumbled over the question on the London radio station LBC 97.3, putting the Conservatives under further pressure over their response to squeezed household budgets.
"I don't buy the value sliced loaf, I've got a breadmaker at home which I delight in using and it turns out in all sorts of different ways," he said. "But you can buy a loaf in the supermarket for well north of a pound."
Told by presenter Nick Ferrari that the true cost was about 47p, he added: "Look, I'm trying to get my children to eat the sort of granary – and they take it actually, they like my homemade bread.