As its name suggests, half-and-half is simply equal parts milk and cream. Whereas heavy cream is just, you know, cream. The real difference lies in the fat content: Half-and-half is 10 to 18 percent fat, and heavy cream falls between 30 and 36 percent. So when is it OK to use up the half-and-half you have on hand in place of heavy cream in a recipe?
For the most part, half-and-half and heavy cream are interchangeable.
Using half-and-half in place of heavy cream can lighten up a pot of clam chowder without any major consequences, and on the flip side, a drizzle of cream instead of half-and-half can add extra richness to a dish of macaroni and cheese.
The only exception to this rule is if you’re making whipped cream: The extra fat in heavy cream holds together all the air bubbles you’re beating in with your whisk. That’s why you also see the label heavy whipping cream being thrown around—the minimum fat content is upped to a porky 36 percent, so it will whip up fluffier and last longer without deflating.