8-Inch to 9-Inch Round Pan Conversion
A 9-inch round pan needs 26.6% more batter than an 8-inch round pan for the same depth. Multiply by 81/64 = 1.265625. Going from 9 inches to 8 inches, use 64/81 = about 0.7901 of the recipe.
- 3 min read
- Updated 2026-10-22
Printable conversion chart
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| Original amount | 8-inch → 9-inch | 9-inch → 8-inch |
|---|---|---|
| 100 g | 126.6 g | 79.0 g |
| 200 g | 253.1 g | 158.0 g |
| 300 g | 379.7 g | 237.0 g |
| 400 g | 506.3 g | 316.0 g |
Weights rounded to 0.1 g. Ratios compare the same number of round layers.
Scale your ingredients
Replace the example in the scaler below with your ingredients, one quantity per line. The starting multiplier is 81/64; change it for your conversion direction or batch size. This scales quantities, not baking time or ingredient densities.
Why one inch changes the batter by more than 12%
Round area grows with the square of the diameter. Dividing 9² by 8² gives 81/64; π and the radius conversion cancel out. This works for one pan to one pan or two 8-inch layers to two 9-inch layers. If the number of layers changes, include that count before dividing total areas.
Keeping the original batch
Pouring an unchanged 8-inch batch into a 9-inch pan makes a layer about 79% as deep. It may bake sooner and look flatter. Putting an unchanged 9-inch batch into an 8-inch pan makes it about 26.6% deeper, so overflow and an underdone center become concerns. Scale down rather than assuming the smaller pan will hold it.
Time cues for the new layer
Keep the recipe temperature and check early. Similar depth is a useful starting point, not a promise of identical time. Watch for the center to set and use the recipe’s doneness test. A wider, thinner layer can dry out while you wait for the old timer; a deeper layer may brown before its center is ready.
Example: resize a two-layer cake
For a recipe using 240 g flour in two 8-inch pans, use 303.75 g flour in two 9-inch pans. Scale sugar, fat, liquids and leavening by the same factor. The scaler above accepts 81/64 directly. If only one of the two pans changes size, make a separate plan for the batter split instead of dividing it equally.
Frequently asked questions
How much bigger is a 9-inch round pan?
It has 26.6% more area than an 8-inch round pan.
Can I use the same batter quantity?
Yes if the fill level is suitable, but the resulting layer depth and baking time change.
What multiplier goes from 9 inches to 8 inches?
Use 64/81, approximately 0.7901.
Does this work for two-layer recipes?
Yes, if the number of layers stays the same.