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.
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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.