How to Use This
Select the pan your recipe was written for and the pan you actually want to use. The calculator divides the two pans' volumes to give you a single multiplier — apply that number to every ingredient in the recipe, including leavening (baking powder/soda), which scales the same as everything else.
Pan Volume Reference
| Pan | Volume |
|---|---|
| 6" Round (2" deep) | 4 cups |
| 8" Round (2" deep) | 6 cups |
| 9" Round (2" deep) | 8 cups |
| 10" Round (2" deep) | 11 cups |
| 8" Square | 8 cups |
| 9" Square | 10 cups |
| 9x13" Rectangular | 14 cups |
| 11x7" Rectangular | 8 cups |
| 9" Springform | 10 cups |
| 10" Bundt | 12 cups |
| 9x5" Loaf | 8 cups |
| 8x4" Loaf | 6 cups |
A round pan's volume doesn't scale the way its diameter suggests — area scales with the radius squared, so a 10" round pan (78 sq in) has more than 50% more surface area than an 8" round pan (50 sq in), not 25% more. This is why eyeballing pan swaps by diameter alone is unreliable, and why the volume-based multiplier above is the more accurate approach.
Why Bake Time Changes With Pan Shape
Even when two pans hold the exact same volume, they won't necessarily bake in the same time if their shapes differ. A wider, shallower pan spreads the batter thinner, so heat reaches the center faster — start checking 10-15 minutes before the original recipe's stated time. A narrower, deeper pan holds the batter thicker, so the center takes longer to set — start checking 10-15 minutes after the original time. Only fill any pan about ⅔ full regardless of size, and bake any leftover batter as a smaller side portion (muffins or a mini loaf) rather than overfilling.
When to Split Into Multiple Pans Instead
If the scaling factor comes out above roughly 1.8-2x, it's often more reliable to bake the recipe twice (or split the batter across two of the original pan) rather than doubling ingredients and guessing at a much longer bake time for an unfamiliar large batch. This is especially true for delicate bakes like sponge cakes, where scaling errors are harder to fix mid-bake than with a denser cake or bar recipe.
When You Don't Know Your Pan's Exact Volume
If a pan is an odd shape or an unfamiliar size not in the chart above, measure it directly rather than guessing from the dimensions printed on the box (manufacturers round inconsistently, and vintage or hand-me-down pans often don't match modern standard sizes exactly). Fill the empty pan with water, one cup at a time, counting as you go, until it's full to the rim — that count is the pan's true volume, ready to use with the scaling factor the same way as any pan in the chart. This water-fill method is also the most reliable way to check a springform or bundt pan, since their fluted or removable-bottom shapes make the standard length-times-width-times-height math unreliable.
Combining Two Smaller Pans Into One Larger One
Two 9-inch round pans (8 cups each, 16 cups combined) don't quite equal one 9x13-inch pan (14 cups) — they actually hold more, not less, which is a common source of confusion when a recipe says "use two 9-inch pans or one 9x13." In practice this works because cake layers in round pans are baked thinner and don't fill to the very top the way a rectangular pan does; if you're converting a recipe the other direction (from a 9x13 to two round pans), split the batter evenly by weight or volume rather than by eye, and expect a very slightly shorter bake time in the rounds since the batter sits shallower.
Frequently Asked Questions
How do I convert a recipe from one pan size to another?
Divide the new pan's volume by the original pan's volume to get a scaling factor, then multiply every ingredient in the recipe by that number. For example, moving from an 8-inch round pan (6 cups) to a 9x13-inch pan (14 cups) means multiplying every ingredient by about 2.3.
What if the new pan is much bigger than what the recipe needs?
If the scaling factor is above roughly 1.8-2x, consider splitting the batter across two of the original pan size instead of scaling the recipe up — it's often more reliable than guessing at a large recipe multiplication, and you avoid ending up with an unusually thin layer in an oversized pan.
Does pan size change the baking time?
Yes. A wider, shallower pan spreads the same amount of batter thinner, so it bakes faster — start checking 10-15 minutes before the original recipe's time. A narrower, deeper pan holds batter thicker, so it takes longer — start checking 10-15 minutes after the original time. Either way, use a toothpick test rather than trusting the clock alone.