Full answer
The US customary system defines one cup as exactly 16 tablespoons. This relationship is the single most useful conversion to memorize for cooking and baking, since most recipe measurements toggle between these two units.
Breaking it down further: a half cup contains 8 tablespoons, a third cup is roughly 5 tablespoons plus 1 teaspoon, and a quarter cup is 4 tablespoons. Going the other direction, each tablespoon holds 3 teaspoons, so a full cup equals 48 teaspoons.
Note that the US cup (236 mL) differs from the metric cup (250 mL) used in Australia, Canada, and the UK. If you are following a recipe from one of those countries, a tablespoon also varies slightly — the Australian tablespoon is 20 mL versus the US 15 mL standard.
For dry ingredients like flour or sugar, spooning into the measuring cup and leveling off with a straight edge gives far more consistent results than scooping directly from the bag, which can pack 20–30% more ingredient than intended.