Simply put, ground beef is beef muscle (not organ meat) ground or very finely chopped. Which part that muscle comes from determines its flavor, texture, and, to some degree, its fat percentage. Ground beef labels can be quite confusing. Some ground beef is labeled by cut (chuck, sirloin, or round), while some is labeled by percent fat to percent lean.

By law, the maximum fat content in any ground beef is 30% (70% lean). The leanness of specific ground beef products can be determined from the cut of meat (chuck, sirloin, or round), or by the amount of fat that's trimmed before grinding. Of the three cuts most commonly used for ground beef, ground chuck is usually the highest in fat content (around 20% fat), and round is generally the lowest (about 11% fat). Sirloin falls between the two (about 15% fat).

The cut on the label is not necessarily an indication of leanness. By law, all packaged ground beef may have fat added to it, as long as the label says how much. A package labeled "80% lean ground sirloin" is 20% fat -- 5% more fat than a piece of ground sirloin naturally contains.

Look for labels that tell the amount of percent fat to percent lean -- then there'll be no guessing. Or choose a whole piece of chuck, sirloin, or round, and ask the person behind the meat counter to trim and grind it for you.