The recipe says a 9-inch round; your cupboard says an 8-inch square. Can you substitute? Usually yes — if you compare pans the right way. The right way is surface area, not diameter, because two pans with the same area hold batter at the same depth and bake in roughly the same time.
Pan sizes by surface area
| Pan | Area | Closest substitutes |
|---|---|---|
| 6" round | 28 in² | half a 9" round |
| 8" round | 50 in² | 9" loaf (45 in²) |
| 9" round | 64 in² | 8" square (64 in²) |
| 10" round | 79 in² | 9" square (81 in²) |
| 8" square | 64 in² | 9" round (64 in²) |
| 9" square | 81 in² | 10" round (79 in²) |
| 9×13" rectangle | 117 in² | two 8" rounds (100 in²)* |
| 9×5" loaf | 45 in² | 8" round (50 in²) |
| 10-cup bundt | ~92 in² equiv. | 9×13" (scale down ~20%) |
*Close but not exact — expect slightly thicker layers and add a few minutes.
Get the exact scaling factor → Pick the pan the recipe calls for and the pan you own; our free pan converter tells you exactly how much to scale the recipe.The two rules of pan substitution
Rule one: within ±15% of area, bake as written. The batter will sit slightly deeper or shallower, but not enough to change the outcome meaningfully. A 9-inch round recipe in an 8-inch square is a perfect swap; in a 9-inch square (27% bigger) it needs scaling up, or you'll get a thin, dry layer.
Rule two: adjust time, not temperature. Keep the oven where the recipe says. Deeper batter needs longer at the same heat; shallower batter needs less. Start checking for doneness about 10 minutes before the recipe's stated time whenever you've changed pans — a toothpick costs nothing.
What about depth?
Area math assumes similar pan depths (most standard pans are 2 inches). If you're moving a layer-cake recipe into a deep 3-inch pan or a bundt, the center takes noticeably longer to set — lower the temperature by 25°F and expect to add time. Our oven temperature converter can help if your recipe and your oven speak different units.
Once you have your scaling factor, the recipe scaler will apply it to every ingredient in one pass.