Here's the thing about powdered sugar and granulated sugar—many of us (myself included!) have accidentally swapped them in recipes, only to end up with disaster. It's not just a tiny difference; that 3% cornstarch in powdered sugar changes everything. Let me break it down like I'd explain it over coffee.
What's really going on?
Granulated sugar is pure sugar—just sucrose, nothing else. Powdered sugar? It's 97% sugar plus 3% starch (usually cornstarch) to keep it from clumping. That starch isn't just filler—it makes powdered sugar soak up way more moisture. I tested this once: cookies made with powdered sugar instead of granulated spread out like pancakes and got gritty. A friend of mine even called them 'crumbly disaster cookies'—I'll never forget it.
| What it is | Why it matters |
|---|---|
| Granulated sugar | 100% sucrose. Holds shape, helps cookies rise, caramelizes evenly. |
| Powdered sugar | 97% sugar + 3% starch. Absorbs moisture, messes with texture, won't caramelize right. |
Real mistakes I've seen (and made)
Cookie dough with powdered sugar? Cookies spread too thin, turn crumbly. My first batch of snickerdoodles did this—felt like I'd wasted a whole bag of flour.
Frosting with granulated sugar? It just doesn't dissolve. You end up with gritty frosting that won't stick to the cake. I learned this when my sister's birthday cake looked like it had sand in it.
Trying to caramelize powdered sugar? It burns fast, tastes bitter. I once made caramel for a pie and it tasted like burnt regret. (No joke—my dog wouldn't even sniff it.)
Storage tip that saved me
Don't leave powdered sugar in a jar near the sink. Humidity makes it clump like wet sand. I keep mine in an airtight container with a silica gel packet—works like a charm. Granulated sugar? It's fine out in the open. No drama.
Bottom line: These aren't interchangeable. That 3% starch isn't a 'minor detail'—it's the whole reason your cookies spread or your frosting fails. I've learned this the hard way (and so have most home bakers I know). Treat them like different ingredients, not just sugar. Your next batch will thank you.
