Baking Pan Size Conversion: How to Swap Pans

To convert a recipe to a different baking pan size, compare the volume of the two pans and multiply every ingredient by the target volume divided by the original volume. An 8-inch round cake pan holds about 100 cubic inches at 2 inches deep and a 9-inch round holds about 127, so moving up one size means making about 1.27 times the batter.

Getting this right keeps the batter at the depth the recipe was tested for, which is what keeps the baking time and texture right too. The free baking pan converter calculates both volumes and the scaling factor for rectangular, round and tube pans.

Below are the formulas, two worked examples, a pan size chart with metric equivalents, and what to do about baking time after a pan swap.

How to calculate baking pan volume

rectangle or square: volume = length × width × depth
round:               volume = π × (diameter ÷ 2)² × depth
tube or Bundt:       volume = round volume − π × (diameter ÷ 8)² × depth
scaling factor       = target pan volume ÷ original pan volume

Measure inside the pan, across the top edge, and measure depth on the inside wall. When both pans have the same depth, comparing base areas gives the same answer, but volume is safer because pans often differ by half an inch or more.

Worked example: an 8-inch round recipe in a 9-inch round pan

1. Original pan: π × 4² × 2 = 100.5 cubic inches.
2. Target pan: π × 4.5² × 2 = 127.2 cubic inches.
3. Scaling factor: 127.2 ÷ 100.5 = 1.27.
4. Multiply each ingredient: 2 cups of flour × 1.27 = 2.54 cups, so about 2½ cups. Three eggs × 1.27 = 3.8, so use 4.

One extra inch of diameter sounds small, but it adds more than a quarter to the volume. Pouring the original amount into the larger pan gives a thin layer that bakes faster and rises less.

Worked example: a 9×13 recipe in an 8×8 pan

1. Original pan: 9 × 13 × 2 = 234 cubic inches.
2. Target pan: 8 × 8 × 2 = 128 cubic inches.
3. Scaling factor: 128 ÷ 234 = 0.55.

So an 8×8 pan takes just over half the batter. If you would rather bake the whole batch, two 8×8 pans hold 256 cubic inches, about 9 percent more than the 9×13, so the full recipe fits with slightly thinner layers.

Baking pan size conversion chart

Volumes assume straight sides 2 inches (5 cm) deep. Real pans have sloped sides and rounded corners, so their usable capacity is a little lower than these figures.

A few useful matches stand out. A 9-inch round and an 8-inch square hold almost exactly the same amount, so you can swap them freely. Two 9-inch rounds, at 254 cubic inches together, take a full 9×13 recipe. To check other sizes, convert centimeters to inches with the length converter, or base areas with the area converter.

Adjusting baking time and temperature after a pan swap

Baking time follows batter depth. If the scaling factor keeps the batter at the original depth, the time stays close to the original. If it doesn't, adjust:

• Shallower batter bakes faster. Start checking 5 to 10 minutes before the recipe's time.
• Deeper batter needs longer. For much deeper pans, many bakers lower the oven by 25°F (about 15°C) so the edges don't overbake before the center sets.
• Fill cake pans about half to two-thirds full to leave room to rise.
• Test doneness, not the clock. A toothpick in the center should come out clean or with a few moist crumbs.

Glass and dark metal pans also brown faster than light metal. The oven temperature conversion guide covers those adjustments and fan oven settings.

How to use the Baking Pan Converter

1. Open the Baking Pan Converter. Under Original Pan, choose a shape: Rectangle, Round or Tube/Bundt. You can also tap a Quick Preset, such as 9x13x2, 9-inch round or 10-inch tube, to fill in the original pan.
2. Enter the original pan's dimensions in inches: length and width for a rectangle, or diameter for a round or tube pan, plus depth.
3. Under Target Pan, choose the shape and enter the dimensions of the pan you plan to use.
4. Read the Scaling factor, shown with the Original volume and Target volume in cubic inches.
5. Multiply every ingredient by the scaling factor. To do that automatically, open the recipe scaler, set Original Servings to 1 and Desired Servings to the factor, and paste in the ingredient list.

If your pans are measured in centimeters, enter centimeters for both pans. The scaling factor is a ratio, so it stays correct; only the volume figures, labeled in cubic inches, will be off.

Common pan conversion mistakes

• Comparing diameters instead of volumes. A 10-inch round is 25 percent wider than an 8-inch round but holds about 56 percent more batter.
• Ignoring depth. A 3-inch-deep cake pan holds 50 percent more than a 2-inch pan of the same diameter.
• Measuring the outside of the pan. Rims and handles add width. Measure inside edge to inside edge.
• Trusting the math for Bundt pans. The tool subtracts a center tube a quarter of the pan's diameter across, about 2.5 inches in a 10-inch pan, but it cannot see fluted or sloping sides, which hold less. For these pans, fill the pan with water, measure it with a measuring cup, and compare that capacity instead.
• Overfilling to use up batter. Extra batter in a full pan can overflow or sink. Bake the leftover as cupcakes.

Frequently asked questions

How do I convert an 8-inch cake recipe to a 9-inch pan?

Multiply every ingredient by 1.27, or about 1¼. A 9-inch round holds about 127 cubic inches at 2 inches deep compared with about 100 for an 8-inch round.

What pan sizes are equal to a 9×13 pan?

A 9×13 pan holds about 234 cubic inches at 2 inches deep. Two 9-inch rounds (254) or two 8-inch squares (256) hold slightly more, so the full recipe divides between them with slightly thinner layers.

Can I use a 9-inch round pan instead of an 8-inch square?

Yes. At the same depth they hold almost the same volume, 127 versus 128 cubic inches, so you can use the original recipe and a similar baking time.

Does baking time change with pan size?

Yes, because time depends on how deep the batter is. Shallower batter bakes faster and deeper batter takes longer, so check for doneness early after any pan swap.

How do I find the volume of a Bundt pan?

Fill it to the brim with water using a measuring cup and count the cups or milliliters. This is more accurate than a formula because of the center tube and fluted sides.

How full should a cake pan be?

Fill most cake pans about half to two-thirds full. That leaves room for the batter to rise without spilling over.