Quick example
Convert an 8-inch round cake to a 9-inch round pan
With both pans 2 inches deep, the 8-inch round has about 50.3 square inches of base area and the 9-inch round has about 63.6. Divide the target capacity by the original capacity to get a 1.266× recipe multiplier—about 26.6% more batter.
Common pan reference
Approximate area and geometric capacity
| Pan | Base area | Depth | Volume to rim |
|---|---|---|---|
| 8-inch round | 50.27 in² | 2 in | 6.963 US cups |
| 9-inch round | 63.62 in² | 2 in | 8.813 US cups |
| 8-inch square | 64 in² | 2 in | 8.866 US cups |
| 9-inch square | 81 in² | 2 in | 11.22 US cups |
| 9 × 13-inch rectangle | 117 in² | 2 in | 16.21 US cups |
| 8½ × 4½-inch loaf | 38.25 in² | 2.5 in | 6.623 US cups |
These are idealized straight-sided volumes to the rim. Usable batter capacity is lower and varies with pan construction.
Area versus capacity
Depth determines which ratio matters
Equal depths
The volume ratio equals the base-area ratio, so area alone is enough to scale the recipe.
Different depths
The calculator multiplies base area by depth and uses the resulting volume ratio.
Round pans
Base area is π times the radius squared. Small diameter changes produce larger-than-expected area changes.
Square and rectangle
Square area is side squared; rectangular area is length times width.
Bake with judgment
Scaling batter does not scale baking time directly
Never fill a pan to its geometric capacity. Leave the headroom required by the recipe, especially for cakes and quick breads that rise. Pan material, wall slope, batter depth, and oven behavior can change baking time. Start checking earlier when batter is shallower and rely on the recipe's doneness cues.
Common questions
Baking pan conversion FAQ
How do I scale a recipe for a different pan?
Multiply every ingredient by the target pan volume divided by the original pan volume.
Can I use a 9-inch pan for an 8-inch cake recipe?
Yes, but the same batter will be shallower. For equal depths, multiply the recipe by about 1.266 to maintain the original batter depth.
Do I scale baking time by the same factor?
No. Check earlier for shallower batter and use recipe-specific visual, temperature, or tester cues.
Are the listed cup capacities fill amounts?
No. They are geometric estimates to the rim. Safe usable capacity is lower.