How-to

How to convert a recipe for a different pan size (area chart and multiplier grid)

Published October 10, 2026 Last checked October 16, 2026

The one-line method: compare areas, not diameters

To convert a recipe to a different pan, work out each pan’s area, divide the new area by the old, and multiply every ingredient by the result. A 9-inch square recipe going into a 9 x 13 is 117 ÷ 81 = 1.44, so you make about 1.5 batches. The batter ends up the same depth as the original, and the original time is a fair first check.

If you don’t want to rescale, you can pour the original batter into the new pan, but the depth changes. A larger pan gives a thinner layer that bakes faster. A smaller pan gives a deeper layer that bakes slower and may overflow. Either way, you plan the time around that change.

This guide is arithmetic plus published baking guidance from King Arthur Baking. We checked the area figures against King Arthur’s own and recalculated each one. It’s not a kitchen test.

Pan area and volume chart

Sources and math: King Arthur Baking’s alternative pan sizes guide gives 50 square inches for an 8-inch round, about 64 for a 9-inch round (63.6 rounded), 64 for an 8-inch square, 81 for a 9-inch square, 77 for an 11 x 7, and 117 for a 9 x 13. Its pan size guide puts a 2-inch-deep 9-inch round and 8-inch square at about 8.8 cups each, a 9 x 3-inch springform at about 13 cups, and a 9 x 5 loaf at nearly a cup, “almost 20%,” more than an 8.5 x 4.5. Its reducing guide uses 38.25 square inches for the 8.5 x 4.5 loaf. The 10-inch round, half sheet, and the other brim volumes are our arithmetic (1 US cup ≈ 14.44 cubic inches). They assume straight sides and square corners, so real pans hold somewhat less.

Two things in the chart surprise people:

• A 9-inch round holds about 27% more than an 8-inch round, even though it’s only an inch wider. King Arthur gives the same 26.6% figure. A 9-inch recipe in an 8-inch pan can overflow.
• An 8-inch square and a 9-inch round are effectively the same pan. Both are about 64 square inches, so you can swap them without changing the recipe.

Pans vary by brand, and listed dimensions may be measured across the top rim. For a ruler-free answer, fill the pan with water one cup at a time and count. Then plan to fill it with batter only half to two-thirds full, as King Arthur recommends for most butter and oil cakes.

Pan multiplier grid

To skip the division, find the pan the recipe was written for in the left column and the pan you’re using across the top. The number is what you multiply every ingredient by to keep the batter the same depth.

Every cell is the new pan’s area divided by the old pan’s, using π × r² for rounds (an 8-inch round is 50.3 square inches before rounding) and length × width for the rest. Round to a multiplier you can actually measure: 1.27 becomes 1¼, 1.44 becomes 1½, 0.79 becomes ¾. Two groups come out within about 5% of each other, so they swap without rescaling: a 9-inch round and an 8-inch square; and a 10-inch round, a 9-inch square, and an 11 x 7.

How deep will the batter be?

Depth is what sets bake time, and it’s simple to work out: batter volume ÷ pan area = depth. One US cup is about 14.44 cubic inches. Take 6 cups of batter, roughly 87 cubic inches. That’s about what King Arthur’s Classic Birthday Cake makes, enough for two 9-inch layers or one 9 x 13, according to its cake-to-cupcake guide.

The last column is the useful one when you don’t know the recipe’s original pan. Measure your batter in a large measuring jug and pick a pan that can take it. It’s based on King Arthur’s advice not to fill a cake pan more than two-thirds full, and it assumes straight sides, so a real pan with sloped sides and rounded corners holds a little less. Less batter than that is fine; it just bakes thinner and sooner. Two-layer recipes split the batter, so 6 cups across two 9-inch rounds is about 3 cups, and about 0.7 inch deep, in each.

Measuring a pan with sloped sides

Most metal and glass pans are wider at the rim than the base, and the listed size may be measured across the top. For area math, measure the inside at the top and at the bottom and use the average. A “9 x 13” that measures 8 x 12 at the base has an average of 8.5 x 12.5, or about 106 square inches, not 117. That 10% difference is why a recipe can run deeper in your pan than the chart predicts. If you’d rather not measure, fill the pan with water a cup at a time and use the volume instead.

The ratio method, step by step

1. Measure both pans across the inside. Diameter for rounds, length and width for rectangles. If the sides slope, average the top and bottom measurements, as above.
2. Calculate both areas. Rectangles: length × width. Rounds: 3.14 × radius × radius (the radius is half the diameter).
3. Divide the new area by the old. That’s your multiplier.
4. Multiply every ingredient by it, leavening included, and round sensibly. A 1.44 multiplier can become 1.5 for most home bakes if the new pan has room.
5. Keep the oven temperature. The batter depth is close to the original, so the time is too. Check a few minutes early and go by doneness.

Weighing makes step 4 much easier. If the recipe gives grams, multiply them directly. If it gives cups, our cups to grams guide explains why each ingredient needs its own conversion.

Worked conversions

One correction while checking: King Arthur’s alternative-pans article calls two 8-inch rounds “about 9% short” of a 9 x 13. By the article’s own areas (2 × 50 = 100 against 117), it’s closer to 15% short. The direction of the advice is the same. The batter will be deeper than intended.

What if you don’t rescale? Adjusting depth and time

Sometimes you just want to bake the original batch in the pan you have.

Into a bigger pan: thinner, faster

King Arthur’s pan size guide says it’s “always better to bake a recipe in a slightly larger pan than a smaller one.” The batter is shallower, so the center sets sooner. Their advice is to start checking “about 10 to 15 minutes before the suggested bake time.” Expect flatter layers or thinner bars.

Into a smaller pan: deeper, slower, riskier

Deeper batter can need 10 to 15 more minutes, by King Arthur’s estimate. Butter cakes can dry at the edges while the middle catches up, and a full pan can overflow. Don’t fill past two-thirds. Spoon the extra into a few muffin cups. Bars in a smaller pan come out thicker and need a longer bake.

Into a Bundt: plan for more time

A Bundt cake is deeper than a layer. King Arthur’s alternative-pans guide says a cake baked in a 10-cup Bundt needs about 30% longer than in a 9 x 13, and about 15–20% longer in a 12-cup Bundt. A standard butter or oil cake of about 6 cups of batter is a good fit for a 10-cup or larger Bundt. Grease the pan’s detailing well. Sponge, chiffon, and angel food cakes aren’t good candidates for pan swaps.

Into a loaf pan: scale down at least 20%

Going from a 9 x 5 to an 8.5 x 4.5 loaf, King Arthur advises scaling the recipe down by at least 20%. That matches the area math (38.25 ÷ 45 = 0.85) plus the slope of the sides. Quick breads in a loaf are deep, so use a tester in the center.

Glass, dark metal, and depth

Material changes the timing too. King Arthur notes glass or stoneware dishes may need a slightly longer bake, possibly at a lower temperature. Dark pans tend to brown edges faster than light aluminum. These effects are smaller than a wrong pan size but add to it, so check early the first time you use a new pan.

Recipes you shouldn’t convert casually

• Cheesecake and anything in a springform: King Arthur advises against swapping standard pans for a springform. Depth and water-bath setups are part of the recipe.
• Foam cakes: angel food, chiffon, and sponge rely on pan shape and sides.
• Yeast bread: a loaf’s size and shape affect rise and bake. Use a dough weight per pan from a tested recipe, and check with a thermometer.

If you’re halving into a smaller pan, the timing rules are in does baking time change when you halve a recipe. If you’re going bigger, see how to double a cake recipe.

Doing the conversion in Sous Chef

A pan change touches the whole recipe: every quantity, the pan line in step one, and the bake time near the end. In Sous Chef on iPhone you can ask “I only have a 9 x 13, adjust this,” and the edit can change both the ingredient lines and the steps that mention the pan or check time. Every change is validated before it applies, edited lines are marked, and the original recipe stays as it was. It’s still a suggestion, not an oven test. Go by the doneness cues. For one quick conversion, a calculator and the chart above are all you need. Sous Chef is free to download and try; heavier AI use may need a subscription later.

Common questions

How do I convert a recipe from a 9-inch round to a 9 x 13 pan?

Multiply the ingredients by about 1.8 (117 ÷ 64). Many bakers simply double, which makes the batter about 9% deeper, so a slightly longer bake is likely. Check at the original time and use a tester.

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

Yes. Both are about 64 square inches, so the recipe, temperature, and time can stay the same.

How much bigger is a 9-inch round than an 8-inch round?

About 27% more area: roughly 64 square inches against 50. That’s enough for a 9-inch recipe to overflow an 8-inch pan, so scale it to about 0.8× or bake the extra batter separately.

How do I find the volume of a Bundt or odd-shaped pan?

Fill it with water a cup at a time and count. Plan for batter to fill about half to two-thirds of that volume, and expect a Bundt to bake longer than a 9 x 13. King Arthur estimates about 30% longer for a 10-cup Bundt.

Do I change the oven temperature for a different pan size?

Usually not. Keep the tested temperature and change when you check: earlier for a shallower bake, later for a deeper one. Glass dishes are the common exception, where a slightly lower temperature may help.

Is a half sheet pan twice a 9 x 13?

By area it’s closer to 1.75×, about 204 square inches inside against 117, but it’s only about an inch deep. It suits thin sheet cakes and bars, not a deep 9 x 13 cake recipe doubled.