Cake Pan Size Converter

Pans swap by volume, not by the inch printed on the rim

An 8-inch round and a 9-inch round do not hold the same batter. Area grows with the square of the radius. This page treats batter height as 2 inches and computes cubic inches, then divides destination volume by starting volume. That quotient is the scale factor for every ingredient.

The volumes used here are: 8-inch round 100.5 cu in, 9-inch round 127.2, 10-inch round 157.1, 8-inch square 128, 9×13 inch 234, bundt 192, 9×5 loaf 96. Those round numbers are π r² h with r in inches and h = 2, except the square, sheet, loaf, and bundt, which use the box or a typical 12-cup bundt working volume.

School bake sales and birthday sheets fail when someone pours an 8-inch batter into a 9×13 and wonders why the cake is a pancake. Scale the recipe, or accept a thin cake and a shorter bake.

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How to use the cake pan converter

Select the pan the recipe assumes. Select the pan on your counter. Read the scale as a percent of the original recipe. 100 percent means the volumes match. 184 percent means you need almost two recipes of batter.

Fill pans about two-thirds full so the cake can rise. A bundt that is brim-full will weld itself to the oven floor.

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Formula and an 8-inch to 9-inch move

Scale = volume_to ÷ volume_from. Round volume = π × (diameter ÷ 2)² × 2. For 8 inches: π × 16 × 2 = 100.53, stored as 100.5. For 9 inches: π × 20.25 × 2 = 127.23, stored as 127.2.

Moving an 8-inch recipe into a 9-inch pan: 127.2 ÷ 100.5 = 1.266, shown as 127 percent of the original recipe. Multiply flour, sugar, eggs, and liquid by 1.27, or mix the original batter and accept a slightly shorter 9-inch layer.

Moving a 9-inch layer (127.2) into a 9×13 (234): 234 ÷ 127.2 = 1.84, or 184 percent. That is almost two full 9-inch batters. One 9-inch batter in a 9×13 makes a thin snack cake. Bake time drops.

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Measure the pan you actually own

Measure inside diameter or inside length, not the outer rim. A "9-inch" pan that is 8.5 inches across inside is an 8.5-inch pan. ARS conversion tables list 1 inch = 2.54 cm if your ruler is metric.

Springform pans leak batter. Match volume, then line the bottom. Dark metal pans brown faster. The scale factor does not change the oven setting by itself, but thinner batter in a dark 9×13 needs an earlier toothpick check.

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What to do with 79 percent versus 184 percent

Under 90 percent: you will have leftover batter. Bake cupcakes with the extra, or reduce the recipe. Over 120 percent: multiply the recipe or bake two smaller cakes. Near 100 percent (8-inch square at 128 versus 9-inch round at 127.2) you can pour as written.

Eggs do not scale to 0.3 of an egg gracefully. For odd percents, scale flour and sugar on a scale, then use a beaten egg by weight (a large egg without shell is about 50 g).

If the scale factor is 79 percent, you can mix the full 8-inch batter and hold back a muffin's worth. That is easier than multiplying every line by 0.79 on a sticky card in a loud kitchen.

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Time, frosting, and the sugar in a class cake

Thinner cakes finish sooner. Start checking 8 to 12 minutes earlier than the original recipe when you move into a larger footprint. Deeper cakes (bundt, loaf) need more time and a lower rack.

Scaling a recipe also scales sugar. AHA child guidance still uses about 25 g of added sugars per day after age 2. A frosted 9×13 for a class is a celebration food, not a daily lunch. This converter will not compute a calorie-percent sugar cap. It only scales batter volume.

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Egg cakes still follow leftover time

A baked sheet sitting in a classroom for the afternoon is a time-and-temperature problem. FSIS leftover advice still starts the 2-hour clock when the cake leaves a hot or cold hold. Cream-cheese frosting makes the clock stricter in practice. Send unfrosted squares when the party is long and the room is warm.

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A class sheet is not two stacked birthday layers

Two 9-inch layers stacked with frosting are a different party than one 9×13. The 184 percent scale fills the sheet with batter. It does not give you two layers. If you need height for candles, bake two 9-inch pans at 100 percent each, or use the 10-inch scale and split the batter.

Cupcakes are about 1/2 cup of batter each in a standard well, roughly 7 to 8 cubic inches. A 9-inch volume of 127 cu in is theoretically 16 cupcakes if you filled every well to that mark. In practice you get 18 to 24 because wells are not filled to a 2-inch cake height. Use a tested cupcake recipe when the form factor matters more than the math.

Gluten-free mixes rise less. Scaling a gluten-free box into a larger pan can give you a sad, thin square. Keep the pan the box names, or scale and accept a snack-cake height.

A loaf pan at 75 percent of a 9-inch layer will overflow if you pour 100 percent of a layer batter into it. That 96 cu in number is a warning. Bake the extra batter as cupcakes.

Write the scale percent on the recipe card in pencil. Next year's volunteer will thank you when the only clean pan in the church kitchen is a 9×13 and the card still says "two 8-inch rounds." Pencil erases when you buy a new pan with a different inside measure next year at the same bake sale table in the gym.

Take a photo of the pan stamp before you leave the kitchen.

Bundt cakes need a greased-and-floured web of corners. Scaling to 151 percent of a 9-inch layer fills a 12-cup bundt only if you also have enough batter to climb those corners. A single 9-inch batter in a bundt makes a short ring. Bake it anyway if you accept a shorter cake, and start checking early.

Sheet pans that are 13×18 (half sheet) are not the 9×13 row. A half sheet at 2 inches would be 468 cu in, twice 234. You would need about 368 percent of a 9-inch recipe. Most school "sheet cakes" are 9×13 or 11×15. Measure.

Leavening scales with the percent, but a 184 percent recipe in one bowl can overflow a home mixer. Mix in two batches. The geometry does not care about your mixer rim.

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Limits of a 2-inch volume model

Angel food, chiffon, and cheesecake do not scale like a butter cake. Foam cakes need a tube pan. Cheesecake needs a water bath and a springform, not a 9×13 multiply.

A 6-cup bundt is not the 192 cu in row. If your bundt is stamped 6 cups, it is closer to half of 192. Measure with water: 1 US cup is 14.4 cubic inches (236.588 mL). NIST volume units let you turn those cups into cubic inches if you want a custom scale.

Flour density still matters when you scale by cups instead of grams. Prefer grams after you have the percent.

A silicone loaf that slumps in the oven has the same cubic inches and a different height. Support it on a sheet pan so the sides do not bow.

Do not scale a boxed mix by this percent unless you also scale the listed water and oil. The box is one unit of chemistry, not a loose pile of flour.

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How it works

Round volume uses π r² h with a 2-inch batter height. Fill pans about two-thirds full so the cake can rise.

Frequently asked questions

• Bake time after scaling?

  Thinner batter in a larger pan finishes sooner. Start checking 5 to 10 minutes early.

Related calculators

References

1. NIST. SI Units - Volume
2. USDA ARS. Measurement conversion tables
3. NIST Office of Weights and Measures. Metric Household
4. USDA Agricultural Research Service. FoodData Central
5. NIST. NIST Handbook 44 (2024) Appendix C, general tables of units of measurement
6. USDA and HHS. Dietary Guidelines for Americans, 2020-2025
7. Vos et al., American Heart Association. Added Sugars and Cardiovascular Disease Risk in Children
8. USDA FSIS. Leftovers and Food Safety