Pan conversion
calculator
Recipe wants a 9×13; you own an 8×8. Pans convert by surface area — compare any two common pans, get the batter factor, and see what happens to depth and bake time.
Pans convert by area
For typical layer-depth bakes, what matters is surface area — batter spread over more or fewer square inches. Rectangles are length × width; rounds are πr², which is why a 9-inch round (≈64 in²) substitutes almost perfectly for an 8×8 square (64 in²).
So: halve the recipe for an 8×8, or make 2× 8×8 from one 9×13.
Depth is the catch
Pour unscaled batter into a smaller pan and it sits deeper — centers bake slower and can sink; go shallower and edges race ahead. Rough guide: within ±10% of area, bake as written; beyond that, scale the batter by the factor above (the recipe converter applies it) or adjust time — deeper bakes get 5–15 minutes more at the same temperature, shallower ones get checked early. The toothpick test outranks every clock.
Pan conversion FAQ
Yes with adjustment — the 8×8 has 55% of the area, so halve the recipe (the small surplus adds slight depth), or expect a much deeper, slower bake from full batter.
Nearly — π×4.5² ≈ 63.6 in² versus 64 in². They substitute for each other without any scaling.
By depth: deeper batter needs more time (roughly 5–15 minutes at the same temperature), shallower needs less — start checking early. Doneness cues beat the clock.
Same-diameter rounds have the same area, so yes for conversion purposes — just note springforms can leak very liquid batters.