You might be tempted to proceed with the recipe as written, but not so fast. While a 9-inch pan doesn’t sound that much larger than an 8-inch pan, a 9-inch round is actually more than 25 percent bigger than an 8-inch. So your cake will not only be thinner, but it can also overbake.
Finding that conversion factor is a straightforward matter of dividing the area of the desired pan by the area of the original pan. You then multiply each ingredient by that percentage.
Or, if you’re not up for dusting off your math skills, just consult our chart below. We’ve done the calculations for you for the most common pan sizes.
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How to Make Your Baking Recipe Fit a Different Pan
As long as the height of your desired pan is the same as the original pan, you can make a swap (though be sure to read through our “More Tips for Success” section below before doing so).
Just use the below chart to determine your conversion percentage, then multiply each ingredient in your recipe by that number. For example, to bake a 9-inch round cake in a 13 by 9-inch pan, multiple each ingredient by 1.8. And note that for some conversions, you won’t need to scale your ingredients at all.
More Tips for Success
1. Round awkward fractions. Instead of trying to measure, say, 2.37 teaspoons, round up to 2.5.
2. To measure part of an egg, beat a whole egg and then measure out what you need. A standard large egg translates to about 4 tablespoons, so 2 tablespoons would give you half an egg.
3. Consider your equipment. With a smaller volume, will the recipe still work in a stand mixer, or would a hand mixer work better? With a larger volume, will you need to make two batches?
4. Don’t rely on the times in the recipe. Bake times as well as mixing or processing times can change when you’ve scaled a recipe. Use visual cues if provided.
5. Keep expectations realistic. While knowing this simple math can really improve your results, don’t forget that baking relies on precision, and your recipe may not bake up exactly like the original.