For most standard recipes (cookies, muffins, cakes), you can swap them one-for-one by volume—one cup of brown sugar for one cup of white sugar. It’s literally that simple. Don’t overthink it.
If you’re feeling brave, try a half-and-half mix. Use half white sugar for crispness and half brown sugar for chewiness and flavor. You get the best of both worlds. It’s like being the diplomat of your own dessert.
Notice I said by volume, not by weight. Brown sugar is denser, so a cup of brown sugar weighs more than a cup of white. But for home baking, volume is totally fine. You’re not building a rocket; you’re making something delicious.