Round baking pans: scale by area, not by diameter
Use the squared diameter ratio to scale ingredients while keeping batter depth comparable.
Method
Changing a round pan’s diameter changes its base area by the square of that change. If the original and replacement pans have straight sides and you want the same batter depth, scale the recipe using their internal base areas. This answers an ingredient-quantity question; it does not calculate a baking time.
Circle area is π times radius squared. Because radius is half the diameter, the area ratio simplifies to replacement diameter squared divided by original diameter squared. Measure both internal diameters in the same unit. A 20% larger diameter gives 44% more area, not 20% more, because both horizontal dimensions increase.
- Internal diameters20 cm → 24 cm
- Area ratio(24 ÷ 20)² = 1.44
- Scale an ingredient300 g × 1.44 = 432 g
Use the squared diameter ratio to scale ingredients while keeping batter depth comparable.
Worked example
Moving from a 20 cm round pan to a 24 cm round pan gives a factor of 1.44. An ingredient amount of 300 g becomes 432 g. A second ingredient of 150 g becomes 216 g, and 200 g of liquid becomes 288 g. Multiply every scalable ingredient by the same factor rather than increasing only flour or only liquid.
In Baking pan scaler, enter original diameter 20, target diameter 24 and ingredient amount 300 to obtain 432 in the same unit. Repeat for the other ingredients, or use Recipe scaler with a ratio of 1 to 1.44. If an ingredient must be divided, measure a suitable fraction by weight when practical. Do not treat the pan-area factor as a serving count or a time multiplier.
(24 ÷ 20)² = 1.44
300 × 1.44 = 432 g
150 × 1.44 = 216 g
200 × 1.44 = 288 g
- Ingredient 1: original
- 300 g
- Ingredient 1: scaled
- 432 g
- Ingredient 2: original
- 150 g
- Ingredient 2: scaled
- 216 g
Both ingredients are multiplied by 1.44. All bar values are masses in grams.
Checks and limits
This shortcut compares round bases at comparable intended batter depth. Different shapes, sloping sides, centre tubes, pan materials or a changed fill depth need further checks. A taller pan does not mean it should be filled to the rim. Follow the recipe’s fill and doneness guidance and allow room for expansion; geometry alone cannot guarantee the finished bake.
Related calculators
Source: King Arthur Baking