How to use this calculator
Choose the shape of each pan and measure its inside dimensions. For a square, enter the same length and width. Use the measurement-system selector for inches or centimeters. Enter an ingredient amount to see how the area ratio scales it.
The formula
A worked example
An 8 inch round pan has an area of about 50.27 square inches. A 10 inch round pan has 78.54 square inches. The factor is 1.5625, so an ingredient listed as 200 g becomes 312.5 g. An 8 × 8 inch square to a 9 × 13 inch rectangle instead uses a factor of 117 ÷ 64 = 1.828125.
Assumptions & limitations
Straight-sided round or rectangular pans with equal batter depth. Excludes tube pans, bundt pans, tapered sides, and pan-count changes. It does not predict baking time. Check capacity and leave room for the batter to rise.
Common questions
Can I switch from round to rectangular?
Yes. Choose each shape separately. The calculator compares base areas, preserving batter depth rather than overall pan capacity.
Do I also scale baking time?
No. Pan material, shape, batter, and oven behavior can change baking time. Check doneness instead of multiplying time by the ingredient factor.
Units reference
The calculation follows the method above. This reference supports the units and conversions.
NIST: units and conversion factors ↗Formula and worked example checked against automated test cases. About our methodology.