Calculateus

Baking Pan Converter

Convert a recipe from one baking pan size to another using each pan's surface area.

Result

Scale Factor
×0.54
9×13" rectangular Area
117 sq in
9" round Area
64 sq in

Your pan has less surface area than the recipe was written for - batter will be deeper, so it will likely need more time than the original recipe.

About the Pan Size Converter

A recipe written for a 9x13 pan doesn't translate directly to a round cake pan or a loaf pan - what actually matters is the pan's surface area, since that determines how thick the batter sits and how it bakes.

How It Works

The calculator looks up the interior surface area of both the pan the recipe was written for and the pan you're actually using, then divides to find a scale factor for adjusting ingredient amounts.

scale factor = area of your pan ÷ area of the recipe's pan

Examples

9x13 recipe into a 9-inch round

A 9x13 pan has 117 sq in of area; a 9-inch round has about 63.6 sq in - a scale factor of about 0.54, meaning roughly half the ingredients and a shorter bake time.

8-inch round into two 9x13 sheet cakes

Going from a small pan to a much larger one (high scale factor) means significantly more batter is needed and the bake will likely take longer despite being shallower, since total volume increased.

Advantages

  • Covers 10 common pan shapes and sizes with accurate surface area figures
  • Gives qualitative bake-time guidance based on whether the new pan is shallower or deeper
  • Works in both directions - scaling up or down

Common Mistakes

  • Assuming any pan swap works with unchanged ingredient amounts and bake time
  • Comparing pans by their stated dimensions instead of actual usable area
  • Not checking for doneness earlier when switching to a shallower pan

Edge Cases to Watch For

  • A scale factor doesn't tell you the new bake time directly - a shallower pan (higher scale factor) bakes faster, and a deeper pan (lower scale factor) bakes slower, but the exact adjustment depends on the specific recipe.
  • Pan shape (round vs. square vs. rectangular) affects heat distribution somewhat independently of area, so results can vary slightly even between pans of similar surface area.
  • This calculation assumes a similar fill depth is desired - very deep or very shallow pans relative to typical baking depth may need more than a simple area-based adjustment.

Common Use Cases

  • Substituting a pan you own for the one a recipe calls for
  • Splitting a 9x13 recipe into round layer cakes
  • Converting between metric and US pan sizes
Written & fact-checked by the Calculateus TeamLast updated August 5, 2026How we verify our formulas

Frequently asked questions

Should I scale the ingredient amounts too?

Multiply every ingredient by the scale factor shown, just like scaling a recipe for more or fewer servings - a scale factor of 0.75 means using three-quarters of each ingredient.

Does this tell me the exact new bake time?

No - pan depth changes bake time in a way that depends on the recipe (cakes vs. bars vs. cookies behave differently), so there's no reliable universal formula. As a rule of thumb, a shallower pan (scale factor above 1) bakes faster and a deeper pan (below 1) bakes slower - start checking 15-20% earlier or later than the original time and use a toothpick test.

Related calculators

Ingredient ConverterConvert cooking ingredients between cups, grams, tablespoons and ounces using real ingredient density, not a generic volume-to-weight guess.Oven Temperature ConverterConvert oven temperature between Fahrenheit, Celsius, and UK Gas Mark for any recipe.Air Fryer ConverterConvert a conventional oven recipe's temperature and cook time to air fryer settings.Recipe ScalerScale a recipe up or down to a new number of servings, converting every ingredient amount proportionally.

Conclusion

Surface area, not the pan's labeled dimensions, is what actually determines how a recipe bakes in a different pan. Scale the ingredients by the area ratio, then treat the original bake time as a starting point rather than a guarantee - check a few minutes early if your pan is shallower than the recipe's.