Cake Pan Size Converter
The recipe calls for a pan you don't own? Enter both pans and get one number: what to multiply every ingredient by.
Use the same unit (inches or cm) for both pans — the result is a ratio, so it works either way.
How pan conversion works
The converter compares the two pans' surface areas. A round pan's area is π × (diameter ÷ 2)²; a rectangular pan's is width × length. The multiplier is simply the new pan's area divided by the original's.
Scaling by area keeps the batter depth the same, and depth is what controls how a cake bakes. Same depth means the original temperature and bake time remain good starting points — just start checking a few minutes early, since ovens and pans vary.
Why going from 8″ to 10″ isn't "a bit more"
Pan area grows with the square of the diameter. An 8-inch round holds about 50 sq in; a 10-inch holds about 78.5 — that's 56% more batter, not 25%. Under-scaling is the usual reason a cake in a bigger pan comes out thin, dry, and overbaked.
Common swaps
| 8″ round → 9″ round | × 1.27 |
|---|---|
| 9″ round → 8″ round | × 0.79 |
| 8″ round → 9×13″ rect | × 2.33 |
| 9×13″ rect → 8″ square | × 0.55 |
| 8″ square → 9″ square | × 1.27 |
Eggs are the awkward ingredient — you can't add 1.56 eggs. Round to the nearest half egg (beat one and use part of it), and let the flexible ingredients absorb the difference.