Baking Pan Size Conversion Calculator

How it works

A recipe fills a pan to a certain depth. To get the same depth in a different pan, the amount of batter has to change in proportion to the pan's bottom area: a round pan's area is π × (diameter ÷ 2)², a square or rectangular pan's is length × width. The scale factor is the new pan's area divided by the original's; with several pans, their areas are added.

When the pans differ in depth, comparing volumes (area × depth) is closer to how much each pan holds. Bundt and muffin pans have no simple bottom area, so they are compared by volume only: a Bundt pan by the brim-full capacity marked on it, a muffin pan by the number of cups times the capacity of each.

If the recipe is not scaled, the same batter spread over a different area comes out deeper or shallower in proportion to the ratio of the areas, which the calculator reports for flat pans.

Formula

round area = π × (diameter ÷ 2)²;  square = side²;  rectangle or loaf = length × width
volume = area × depth;  Bundt = rated capacity;  muffin = cups × capacity per cup
total = one pan × number of pans
factor = new total ÷ original total  (area, or volume)
unscaled batter depth change = original area ÷ new area − 1

Example

A recipe for one 9 × 13 in pan (117 sq in) baked in two 9 in rounds (2 × 63.6 = 127.2 sq in) scales by 127.2 ÷ 117 = 1.087; left unscaled, the batter is 8.0% shallower.

From one 8 in round (50.3 sq in) to one 9 in round (63.6 sq in) the factor is 81 ÷ 64 = 1.266, and an unscaled 9 in recipe in the 8 in pan is 26.6% deeper. Both pans 2 in deep hold 6.96 and 8.81 cups.

Assumptions and limitations

• Pans are treated as straight-sided. Loaf, square and rectangular pans usually flare outward and have rounded corners, so their true capacity differs a little from length × width × depth.
• Volume compares brim-full capacity. King Arthur Baking notes that a Bundt pan's bakeable capacity is well below its rated capacity: about 6 cups of batter for a 10-cup pan (PJ Hamel, 2016, updated 2020).
• The capacity per muffin cup is a typical value, not a published standard; it varies by pan and is editable. The default of 0.3 cup brim-full is derived from King Arthur Baking's report that the roughly 6 cups of batter from its Classic Birthday Cake makes 24 to 30 cupcakes with each cup filled about four-fifths full (Kye Ameden, 2019): 0.2 to 0.25 cup of batter per cup ÷ 0.8 = 0.25 to 0.31 cup brim-full.
• Baking time changes with batter depth and pan material, and no published model gives the new time; it is not calculated, and doneness has to be checked. King Arthur Baking reports a larger pan often bakes faster and a smaller, deeper one may need 10 to 15 minutes longer.
• Pan comparisons follow King Arthur Baking: PJ Hamel, "The essential alternative baking pan sizes" (2019, updated 2020) and Bronwen Wyatt, "Why the size of your baking pan matters so much" (2025).

Frequently asked questions