Baking Pan Size Conversion: Free Calculator (9x13 to 8x8, Round, Bundt & More)

For Zainab's seventh birthday, she chose a chocolate cake from a recipe card that called for a 9×13 pan. I had promised her a tall, round layer cake with sprinkles on the sides, and all I owned were two 8 inch round pans. I poured the batter in, filled both pans almost to the top, and slid them into the oven feeling very proud of myself. Twenty minutes later, chocolate batter was dripping onto the oven floor and the kitchen smelled like smoke.

My mother would have laughed. In her kitchen in Karachi, she baked every cake in the same dented round tin, and when a recipe made too much batter, she simply poured the extra into a steel katori and baked a little cake for whoever was helping her. She never measured a pan in her life. I, on the other hand, clearly needed some help.

That smoky birthday taught me that baking pan size conversion is really just a little geometry. A 9×13 pan holds almost twice as much batter as an 8 inch round, so my two pans had been asked to hold far too much. Once I understood that, I could bake any recipe in any pan I owned, from Bundt pans to cupcake tins, without wasted batter or burnt ovens.

I built this free calculator so you never have to learn that lesson the hard way. Choose the pan your recipe uses and the pan you want to use, and it tells you exactly how much to make, how many pans or cupcakes the batter will fill, and how to adjust the bake time. You can even paste your ingredient list and get it scaled to the new pan. Below the tool, I share the charts and rules I bake by.

BAKING PAN SIZE CONVERTER

Choose your two pans, add the original bake time if you have it, and your answer appears below. You can also paste your ingredients to scale them.

HOW TO USE THE PAN SIZE CALCULATOR

1. Choose the pan your recipe uses. Pick from squares, rectangles, rounds, springforms, loaf pans, Bundt pans, pie plates and muffin tins, or enter a custom size in inches or centimetres.
2. Choose the pan you want to use. The calculator compares how much batter each pan holds.
3. Read your answer. You will see whether to use the recipe as written, make half, make one and a half times as much, or how many cupcakes the batter makes.
4. Add the bake time and temperature. The calculator estimates the new bake time and tells you if the oven should go lower for a deeper pan.
5. Scale your ingredients. Paste the ingredient list and every amount is converted into easy measurements, with a note when the eggs need splitting.
6. Copy and bake. Copy the scaled recipe to your notes, preheat the oven, and you are ready.

THE SIMPLE MATH BEHIND PAN CONVERSIONS

For cakes, brownies and bars, what matters most is the area of the pan, because you want the batter to sit at the same depth. Same depth means the same bake time, the same texture and no overflowing.

• Square or rectangular pans: multiply length by width. A 9×13 pan is 117 square inches. An 8×8 pan is 64 square inches.
• Round pans: multiply 3.14 by the radius squared. The radius is half the diameter, so a 9 inch round is 3.14 × 4.5 × 4.5, or about 64 square inches.
• Your scaling number: divide the new pan's area by the original pan's area. From a 9×13 to an 8×8, that is 64 ÷ 117 = 0.55, so you make about half of the recipe.

Deep pans like Bundt pans and loaf pans are different, because the batter sits much deeper. For those, the calculator compares the volume of batter each pan holds instead. As a rule, cake and loaf pans are filled about halfway, and Bundt pans and muffin cups about two-thirds full.

THE MOST COMMON PAN CONVERSIONS

These are the swaps readers ask me about most, worked out with the same numbers the calculator uses.

9×13 to 8×8

An 8×8 pan holds about 55% of what a 9×13 holds, so make half of the recipe. If you would rather keep the full recipe, divide it between two 8×8 pans. This is how I make one of my casseroles for dinner and a second one for the freezer.

9×13 to Round Cake Pans

A 9×13 recipe fills two 9 inch round pans, which makes it ideal for a classic layer cake. In 8 inch rounds, it is a little more than two pans' worth, about 2⅓, which is exactly why my birthday cake overflowed. Use two 8 inch rounds and bake the extra batter as a few cupcakes.

8×8 and 9 Inch Round

These two pans hold almost exactly the same amount, about 64 square inches each, so you can swap them without changing a thing. A 9×9 pan holds about a quarter more, so the cake will be a little thinner and may bake a few minutes faster.

9×13 to a Bundt Pan

A 9×13 recipe fits a 12-cup Bundt pan almost exactly. Because the batter is much deeper, lower the oven by 25°F (15°C) and expect a longer bake. A 30-minute 9×13 cake usually needs about 45 to 55 minutes in a Bundt pan.

9×13 to Loaf Pans

A 9×13 recipe fills about two 9×5 loaf pans. Loaf pans are deep and narrow, so lower the oven by 25°F (15°C), bake longer, and tent the top with foil if it browns before the center is set.

Cake Recipes to Cupcakes

A 9×13 cake makes about 24 standard cupcakes, and an 8×8 or 9 inch round cake makes about 12 to 13. Fill each cup about two-thirds full and start checking standard cupcakes at about 17 minutes. Mini cupcakes usually take 10 to 14 minutes.

9×13 to a Jelly Roll Pan

A 10×15 jelly roll pan is only about 1 inch deep, so it takes about two-thirds of a 9×13 recipe for a thin sheet cake. Watch it closely, because thin cakes can go from done to dry very quickly.

ADJUSTING BAKE TIME AND TEMPERATURE

Baking time depends on how deep the batter is, not on how much batter there is. That is why two 8×8 pans bake in about the same time as one 9×13, while the same batter in a Bundt pan needs much longer.

• Same depth: keep the same temperature and start checking 5 minutes early.
• Thinner batter: keep the temperature the same and check much earlier.
• Much deeper batter: lower the oven by 25°F (15°C) so the outside does not burn before the middle is cooked, and bake longer.
• Cupcakes: bake at the recipe temperature, usually 350°F (180°C), for about 17 to 22 minutes.

The calculator gives you a starting time, but your eyes and a toothpick are the final test. A cake is done when it springs back when pressed lightly, starts to pull away from the sides, and a toothpick in the center comes out clean or with a few moist crumbs. If your recipe is from the UK or uses gas marks, my oven temperature converter will translate the temperature too.

HOW TO SCALE A RECIPE FOR A NEW PAN

Scaling most ingredients is easy: multiply each one by the same number. A few ingredients need a little thought.

• Eggs: when the math gives you part of an egg, whisk the eggs together and measure. One large egg is about 50 grams or 3¼ tablespoons. The scaler in the calculator does this for you.
• Baking powder and baking soda: scale them exactly, and measure carefully. Too much makes a cake rise and then sink.
• Salt, spices and vanilla: scale them as written. If the result is a tiny amount, a scant pinch is fine.
• Weigh when you can: scaled amounts are easier to measure in grams. My cooking measurement converter turns cups and spoons into grams for over 100 ingredients.

Saad has become my official recipe halver. He loves typing the ingredients into the scaler and reading the new amounts out loud while I measure, and he catches me every time I forget to halve the vanilla.

CASSEROLES, BARS AND BROWNIES

The same math works for savory dishes. A 9×13 casserole like my beef enchilada bake or Cheddar Bay green bean casserole splits neatly into two 8×8 dishes, one to bake tonight and one to freeze. Casseroles are forgiving, so you rarely need to change the temperature, but deeper dishes take longer to heat through in the center.

Bars and brownies follow the same rules as cakes. My lazy girl pecan pie bars bake in an 8×8 pan, so for a 9×13 you would make about 1¾ times the recipe. Because bars rely on texture, keep the depth the same and check them a few minutes early.

WHY PAN MATERIAL MATTERS TOO

Two pans of the same size can bake very differently. Here is what to watch for:

• Glass and ceramic dishes: they hold heat longer and brown the edges faster. Many bakers lower the oven by 25°F (15°C) when baking cakes in glass.
• Dark metal pans: they absorb more heat and brown faster. Start checking a few minutes early.
• Light aluminum pans: these give the most even results and are what most recipes are tested in. A good one costs under $15 and lasts for years.
• Cast iron skillets: a 10 inch skillet measures about 9 inches across the bottom, so treat it like a 9 inch round.

WHEN TO DOUBLE OR HALVE INSTEAD

Sometimes the easiest answer is not an exact conversion but a simple one. If the calculator says to make 0.9 or 1.1 times the recipe, just make the recipe as written and adjust the bake time. If it says 0.55, half the recipe is close enough. When you need a larger batch, like a sheet cake for a party, my party food calculator tells you how many servings you need, and you can work backward to the pan size from there.

MY TIPS FOR BAKING IN A DIFFERENT PAN

• Never fill a cake pan more than two-thirds full. Batter needs room to rise.
• Line pans with parchment when you switch shapes, so the cake releases cleanly.
• Bake extra batter as cupcakes instead of overfilling. Little bakers in the house will thank you.
• Put a baking sheet on the rack below the first time you try a new pan, just in case.
• Write the conversion on your recipe card, so next time you do not have to work it out again.

FREQUENTLY ASKED QUESTIONS

These are the pan questions I get most often.

Can I use an 8x8 pan instead of a 9x13?

Yes, but make about half of the recipe, because an 8×8 pan holds about 55% as much as a 9×13. Or keep the full recipe and divide it between two 8×8 pans.

How many 9 inch round pans equal a 9x13?

Two 9 inch round pans hold about the same amount of batter as one 9×13 pan, which makes a 9×13 recipe ideal for a two-layer round cake.

Is an 8x8 pan the same as a 9 inch round?

Yes, almost exactly. Both are about 64 square inches, so you can swap them without changing the recipe or the bake time.

How many cupcakes does a 9x13 cake recipe make?

A 9×13 cake recipe makes about 24 standard cupcakes. Fill each cup about two-thirds full and start checking at about 17 minutes.

Can I bake a 9x13 recipe in a Bundt pan?

Yes. A 9×13 recipe fits a 12-cup Bundt pan. Lower the oven by 25°F (15°C) and expect it to take about 45 to 55 minutes.

How do I adjust baking time for a different pan size?

Bake time depends on batter depth. If the batter is the same depth, keep the time about the same and check early. If it is deeper, lower the oven by 25°F and bake longer. If it is shallower, bake for less time.

How do I calculate the area of a round pan?

Multiply 3.14 by the radius squared. The radius is half the diameter, so a 9 inch round pan is 3.14 × 4.5 × 4.5, or about 64 square inches.

How do I halve a recipe with 3 eggs?

Whisk 2 eggs together and use about 75 grams, or 5 tablespoons, of the mixture. Save the rest for scrambled eggs.

BAKE IN THE PAN YOU HAVE

Zainab did get her round birthday cake in the end. I baked it again the next weekend, two 9 inch rounds this time, with a handful of cupcakes from the extra batter, and nothing dripped onto the oven floor. I hope this calculator gives you the same confidence to bake any recipe in whatever pan is in your cupboard. Bookmark it, and the next time a recipe calls for a pan you do not own, you will know exactly what to do.

Ready to bake? Here are a few of my family's favorites to try in any pan:

• Classic Coffee Cake
• Victoria Sponge Traybake
• Chocolate Zucchini Muffins
• Lazy Girl Pecan Pie Bars
• Blackberry Cobbler with Almond Flour Topping

Happy baking from my kitchen to yours! 🎂🧁