Cake Pan Converter

Background.

Two inches of diameter sounds trivial, yet a 10-inch round cake pan covers 78.54 square inches and an 8-inch round only 50.27. To bake a layer of the same thickness, the bigger pan needs 1.5625 times the batter. Pan area grows with the square of the diameter, which is why swapping pans by eye so often ends in a thin, dry layer or batter creeping over the rim.

The comparison here is by footprint area, the method King Arthur Baking publishes: round pans measured as π times the radius squared, square and rectangular pans as length times width. Matching area keeps the batter at the depth the recipe was designed for, and depth decides how long the centre takes to set and how dark the edges get. Two pans that hold the same volume can still bake quite differently if one is wide and shallow and the other narrow and tall.

There are two ways to act on the answer. Multiply every ingredient by the scale factor, and the batter sits at exactly its original depth in the new pans. Or keep the recipe as written and look at how full the new pans would be: the verdict checks that against the half-to-two-thirds fill range Wilton and King Arthur both give, and the bake-time note tells you whether to start testing early or expect a longer bake.

All dimensions are inside measurements in inches, and capacities are in US cups.

What is cake pan converter?

Converting between cake pans means comparing total base areas: the combined footprint of the pans you will bake in, divided by the combined footprint of the pans the recipe names. The count matters as much as the size. A layer-cake recipe written for a pair of 8-inch rounds has 100.53 square inches to fill, not 50.27. The ratio is the factor applied to every ingredient, flour and salt alike; above 1 the new pans are larger, below 1 they are smaller. A separate figure, each pan's brim capacity, is its volume filled to the top edge, which tells you whether a given quantity of batter can physically fit.

How to use this calculator.

1. 01Choose the shape of the pan the recipe was written for and enter its inside measurements in inches: diameter for a round pan, side for a square, length and width for a rectangle. Measure across the base rather than the rolled rim, because most pans taper slightly.
2. 02Add that pan's depth and how many the recipe uses. Layer-cake recipes usually call for two or three.
3. 03Do the same for the pans you plan to use. A loaf pan counts as rectangular and a straight-sided springform as round.
4. 04Set how full the original pan was. If the recipe does not say, 60% sits in the middle of the half-to-two-thirds range.
5. 05Read 'Multiply the recipe by' if you intend to scale, or the fill percentage and verdict if you would rather bake the recipe unchanged.

The formula.

The scale factor is f = (n₂ × A₂) ÷ (n₁ × A₁), where A is the base area of one pan and n the number of pans; subscript 1 is the recipe's pan and 2 is yours. A round pan's area is π × (d ÷ 2)², a square's is s² and a rectangle's is L × W. Because area follows the square of a length, modest changes in diameter move the recipe a long way.

Capacity is total area × depth in cubic inches, divided by 14.4375 to give US cups. That divisor is exact: the US gallon is defined as 231 cubic inches and holds 16 cups, and 231 ÷ 16 = 14.4375.

The batter the recipe makes is the original pans' capacity times the fill percentage you enter. Poured unscaled into the new pans, it spreads to a depth of batter volume ÷ new total area, and that depth as a share of the new pans' height is the fill percentage reported. The verdict places it in one of four bands: more than the brim, above two-thirds, from one-half to two-thirds inclusive, or below one-half.

The bake-time note compares that unscaled depth with the batter's depth in the original pan. Within 2% either way the timing is treated as unchanged; shallower batter means checking 10 to 15 minutes early, deeper batter up to 10 to 15 minutes longer, following King Arthur's guidance. π is used at full precision, so a 9-inch round comes to 63.62 square inches, a shade under the 64 of the 8-inch square that baking guides treat as its equivalent.

A worked example.

Frequently asked questions.

References& sources.

1. [1]King Arthur Baking Company (2019-04-23). 'The essential alternative baking pan sizes.' Source of the area method — square and rectangular pans compared by length x width, round pans by radius squared x 3.14 — of the 8-inch square and 9-inch round equivalence, of the 117 square inch figure for a 9x13, and of the two-8-inch-round overflow warning.
2. [2]King Arthur Baking Company (2025-08-18). 'Why the size of your baking pan matters so much.' Source of 'fill the pan between half and two-thirds full', of the 8-inch square / 9-inch round volume equivalence (about 128 cubic inches or 8.8 cups), and of the 10-to-15-minute bake-time adjustments in both directions.
3. [3]Wilton Brands LLC. 'Wedding Cake Guide.' Source of 'Fill pans 1/2 to 2/3 full; 3 in. deep pans should be filled only 1/2 full', of the note that its 2-inch batter amounts assume pans two-thirds full, and of the 4 to 5 1/2 cup yield of an average two-layer cake mix.
4. [4]Wilton Brands LLC. 'Cake Bakeware 101: How to Prepare a Cake Pan and More.' Source of 'filling your pans no more than 2/3 full with batter (a little more than half way)'.
5. [5]National Institute of Standards and Technology (2008). 'Guide for the Use of the International System of Units (SI), NIST Special Publication 811', Appendix B.8. The US liquid gallon is exactly 231 cubic inches, so the cup used here is exactly 231/16 = 14.4375 cubic inches.