Cake Pan Size Converter: 9x13, 8x8, Round

How the pan scale factor works

Batter spreads across the floor of the pan. If you want about the same depth of batter in a different pan, scale the recipe by the ratio of the two floor areas. This calculator finds that ratio. Round pans use the area of a circle from the diameter you type: π × (diameter ÷ 2)². The field is a diameter, the distance across the pan, not the radius. Square pans use side × side. Rectangular pans use length × width; the second dimension appears only when you choose rectangular.

Scale factor = new pan area ÷ original pan area. Multiply every ingredient by that factor. A factor of 1.25 means a quarter more of each ingredient. A factor of 0.80 means you keep 80% of each ingredient. The panel also prints both areas in square inches so you can see which pan is actually larger. Areas are the inside floor, so measure across the interior, not the outside handles.

The factor is about volume only in the sense of "same depth." A deeper fill in the same footprint needs more batter and a longer bake, and this page has no depth field. Bake time is not multiplied by the factor. A chart of the common pairs, 9×13, 8×8, 9×9, and 8-, 9-, and 10-inch rounds, is the baking pan conversion chart. It uses this same area function.

8x8 pan conversions

The 8×8 square is the pan home bakers swap most often, so here are its common pairs, each from the same floor-area formula the calculator runs. An 8×8 is 8 × 8 = 64 square inches.

• 8×8 recipe into a 9×13: 117 ÷ 64 = 1.828125, displayed as 1.83. That is less than a full double. A doubled 8×8 recipe in a 9×13 bakes up a little deeper than the original.
• 9×13 recipe into an 8×8: 64 ÷ 117, displayed as 0.55. A little over half the sheet recipe.
• Two 8×8 pans and one 9×13: 128 versus 117 square inches. See the answer box above: 0.91 one way, 1.09 the other.
• 8×8 and a 9-inch round: 64 versus π × 4.5² ≈ 63.62. The factor is 0.99 from the square to the round, so they are nearly interchangeable.
• 8×8 and a 9×9: 81 ÷ 64 = 1.265625, displayed as 1.27. A 9×9 needs about 27% more batter than an 8×8 at the same depth.
• 8×8 and an 8-inch round: 64 versus about 50.27. Not interchangeable: 0.79 from the square to the round.

Every factor here compares floor area only. This page has no depth field, so it does not give quarts or cups of batter. For batter volume at a depth you choose, the baking pan conversion chart works it out from the area.

Worked examples

Example 1: A 9-inch square to a 10-inch round

The square is 9 × 9 = 81 square inches. The round is π × 5² ≈ 78.54 square inches. Factor ≈ 78.54 ÷ 81 ≈ 0.97. The pans are close. Many bakers would bake the original recipe in the 10-inch round and expect a slightly shallower cake. If you want the depth to match, multiply each ingredient by 0.97, which is a small trim.

Example 2: A 9-inch round into a 9×13

A 9-inch round is π × 4.5² ≈ 63.62 square inches. A 9×13 rectangle is 117 square inches. Factor ≈ 117 ÷ 63.62 ≈ 1.84. One layer's worth of batter does not fill a 9×13 to the same depth. You need a bit under a double recipe. Pouring the unscaled batter into the larger pan makes a thin cake that finishes early and dries out at the edges.

Example 3: An 8-inch round versus an 8-inch square

The round is π × 4² ≈ 50.27 square inches. The square is 64 square inches. From the round recipe to the square pan, the factor is 64 ÷ 50.27 ≈ 1.27. The square holds about 27% more batter at the same depth, because the corners add area the circle does not have. Going the other way, square to round, the factor is about 0.79. The earlier habit of calling these pans interchangeable overfills one of them.

Example 4: Two 9-inch layers versus one 9×13

Two 9-inch rounds are about 127.2 square inches together. A 9×13 is 117. The factor from the two rounds to the sheet is 117 ÷ 127.2 ≈ 0.92. A two-layer cake recipe is in the same neighborhood as a 9×13 sheet, close enough that the sheet will be a little fuller if you use the whole recipe. For a nearer match, multiply by 0.92, or accept a slightly taller sheet cake and start checking doneness earlier than a deep round would need.

When to use this

Use it when the pan in the recipe is missing, dirty, or the wrong shape, and you have a different pan whose inside length and width you can measure. Loaf pans are not a separate shape; enter them as rectangles using the inside length and width. A muffin tin is a set of small rounds. Scaling a whole cake recipe into muffins also changes bake time a lot, so treat the factor as a volume hint and rely on a muffin recipe when you have one.

After you have the factor, the Recipe Scaler will rewrite an ingredient list if you can express the factor as a servings change. A factor of 1.5 is the same multiply as going from 4 servings to 6. The Oven Temperature Converter is the place for Fahrenheit, Celsius, and gas mark. It does not take a pan factor, and it should not: temperature usually stays put while time changes.

Common mistakes

• Typing a radius into a diameter field. A 9-inch pan is 9 across. Entering 4.5 makes the area one quarter of the real pan and the factor collapses.
• Scaling flour and leaving the eggs alone. The factor applies to the whole formula if you want the same batter. Partial scaling changes the recipe, not just the yield.
• Multiplying the bake time by the factor. A wider, shallower pan usually finishes sooner. A smaller, deeper pan usually needs longer. Start checking at roughly 70% of the original time and use a toothpick or a thermometer.
• Measuring the outside of the pan. Rolled rims and handles add an inch that is not floor area. Measure the interior.
• Ignoring depth. Area scaling keeps depth similar. If you deliberately fill a pan deeper, you need more batter than the area ratio suggests, and you need more time.

Limitations

No pan depth, no batter volume in cups, and no presets for bundt, tube, or muffin pans. A bundt's center tube removes area; a simple diameter overstates it. Glass, dark metal, and shiny aluminum brown differently at the same oven setting, and the factor will not capture that. Very large factors, roughly double or more, can push a recipe whose structure depends on a specific egg or leavening ratio. At that point a recipe written for the pan is safer than a heroic multiply. Salt, spices, and chemical leaveners are the ingredients bakers most often scale a little more cautiously than the pure area ratio. The cooking measurement myths article is a good reminder that a cup of flour is already an approximate measure before you scale it.

FAQ

Do two 8x8 pans equal one 9x13?

Not exactly. Two 8x8 pans have 128 square inches of floor together, and a 9x13 has 117. The two squares hold about 9% more at the same depth. To move a two-8x8 recipe into one 9x13, multiply by 0.91. To go from a 9x13 into two 8x8 pans, multiply by 1.09.

How do I convert an 8x8 recipe to a 9x13?

Multiply every ingredient by 1.83. That is 117 square inches divided by 64. It is a little less than a double, so a doubled 8x8 recipe makes a slightly deeper 9x13 cake. Bake time does not scale by the factor; check doneness early.

Should salt and baking powder take the same factor?

For a factor near 1, yes. For a large jump, many bakers scale salt, hot spice, and leavening a bit less than the flour and liquid, then adjust. Chemical leavening that is wildly overscaled tastes metallic and can collapse the crumb. If the factor is extreme, find a tested recipe.

Do I change the oven temperature?

Keep the recipe temperature unless the pan material forces a known adjustment, such as lowering the set point slightly for glass. Change the time, and check early. Convection ovens are a separate adjustment from pan size.

What if the factor is exactly 2?

Double every ingredient, and plan on a larger pan or a second pan. Do not pour a double recipe into the original pan. Use the recipe scaler to rewrite the list so a 1/3 cup does not get doubled in your head as "a bit more."

Are square inches the same as cups of batter?

No. Square inches compare the floor. Cups of batter also depend on how deep you fill. If a recipe says "fills a 9-inch round two-thirds full," the area factor estimates a new pan filled to a similar fraction, not a cup count.

Why does a 9-inch round not equal a 9-inch square?

The square's side is 9 inches, so its area is 81. The round's widest point is 9 inches, and the corners are missing, so its area is about 63.6. The shared "9" is a width, not an area.

Practical tips

Measure the inside of both pans before you shop for a substitute, and write the factor on the recipe card next to the pan you actually own. Stay within about a quarter of the original area when you can. Outside that, texture and time drift enough that a purpose-written recipe is worth finding.

Shallow batter browns faster. If the top colors early, tent it with foil and keep baking until the center tests done. Deep batter needs patience and often a lower rack so the bottom is not still raw when the top is finished. Pan color matters here as much as the factor: a dark nonstick pan runs hotter at the edges than a light aluminum pan.

For a dinner you are also scaling by headcount, do the pan factor and the servings factor as two separate questions. Servings change how much food you want. Pan area changes how that food fits. The recipe scaler handles the ingredient list once you know the multiply.

Related calculators

• Recipe Scaler
• Cooking Measurement Converter
• Oven Temperature Converter
• Fraction, Decimal, and Percent Converter
• Baking pan conversion chart
• Recipe halving, doubling, and thirding chart when the servings changed and the pan did not
• Cooking measurement myths