How to Convert Cake Pan Sizes
Swapping pan sizes without adjusting the recipe is why cakes overflow or bake up thin and dry. The key insight: what matters is the pan's area, not its diameter. A 9-inch round has noticeably more area than an 8-inch, so it needs more batter to reach the same height.
Scale by area, not diameter
Area grows with the square of the radius, so going from an 8-inch to a 10-inch pan isn't a 25% increase — it's over 50%. Calculate each pan's area, divide the new by the old, and multiply every ingredient by that factor. This tool does the area math for round pans automatically.
Adjust your bake time
More or less batter changes baking time and, if the depth changes, the rate the center cooks. A wider, shallower cake bakes faster, so start checking well before the original recipe's time and rely on a toothpick, not the clock.
Frequently asked questions
- Can I use a 9-inch pan instead of 8?
- Yes, but scale the recipe up by about 1.27x, since the 9-inch has more area, or expect a thinner cake.
- Do I scale by diameter?
- No — scale by area, which grows with the square of the radius.
- Does bake time change?
- Yes. Different batter volume and depth change timing; check for doneness early.