What size pan will hold half of a batter for a round cake with a diameter of 9 inches?

It is a pan with a diameter of about 6.36 inches, not 4.5 inches. The pan is compared by area. Since the area increases proportionally to the square of the diameter, halving the width does not halve the volume but quarters it. The correct answer is 9 divided by 1.414 which is 6.36 inches. This same relationship also explains why the seemingly small step from an 8 inch pan to a 9 inch pan increases the batter by 27%.

Can a recipe for a 9 by 13 inch pan be baked in a round cake pan?

Yes, two 9 inch round pans are a common alternative. A rectangular pan that measures 13 by 9 inches has an area of 117 square inches while the total area of two 9 inch round pans is 127 square inches. So using round pans will result in about a 9% thinner cake unless you increase the amount of batter. If you set the number of pans to 2 on this page, then that aspect is taken into account by the conversion factor used in the calculation. Be sure to pay attention to your baking time though. The same amount of batter spread out over two flat layers will be done much faster than a single deep pan cake.

Is the shape's height important?

It depends on the type of question so this calculator has different options. The base area method keeps the height of the cake as given in the recipe and ignores the size of the pan. Most conversion tools use this method because it makes it easier to predict cooking time. The volume method takes into account both the heights of the pans, and you fill the pans with an amount of batter that is proportional to the ratio of the height of the pan to the recipe. If the heights are equal then both methods give the same result but if they are different then the results will be significantly different. So when changing from a flat cake tin to a taller sided one or vice versa, the height is most important.

Will the dough run out of the mold?

The calculator will tell you directly. It calculates the depth of batter in the pan and what percentage that is relative to the height of the pan. If it exceeds 100% then the batter will overflow the sides. At about 85% or more, a liner is recommended. The conversion factor alone cannot detect this error since a pan can have sufficient surface area but still be too shallow. Generally, cake pans are recommended to be filled to about half to two thirds to allow room for the cake to rise.

Can this also be used for bundt cake pans or other specialty pans?

For regular cake pans or angel food cake pans this tool can be used. As it is a circular shape with a hole in the middle, the base area can be calculated exactly when given the outside diameter and the diameter of the hole. However it is not suitable for bundt cakes which have ridges. The sloping decorative sides mean that the actual volume is significantly less than what would be guessed from the outline, and there is no formula to accurately represent this shape. For such pans you should fill with water in small increments to measure the volume, then enter that volume into a regular round pan. Also wet sugar based bundt cake batters are usually designed so that the middle cylinder supports the structure, so they are not suitable for flat pans at all.

Cake Pan Calculator - Convert a Recipe to Any Pan Size

Standard pans measured against the pan your recipe calls for. Footprints are geometric, so a real pan with sloping sides holds a little less than the cup figure shown - which is exactly why published capacity charts disagree with each other by about a cup.
Pan	Footprint (sq in)	Holds to the brim (US cups)	Batter at your fill level (US cups)	Multiply the recipe by
6 x 2 in round	28.3	3.9	2.6	0.444
8 x 2 in round	50.3	7	4.7	0.79
9 x 2 in round	63.6	8.8	5.9	1
10 x 2 in round	78.5	10.9	7.3	1.235
8 x 2 in square	64	8.9	5.9	1.006
9 x 2 in square	81	11.2	7.5	1.273
11 x 7 x 2 in rectangle	77	10.7	7.1	1.21
13 x 9 x 2 in rectangle	117	16.2	10.9	1.839
8 x 4 in loaf	32	5.5	3.7	0.503
9 x 5 in loaf	45	9.4	6.3	0.707
15 x 10 x 1 in jelly roll	150	10.4	7	2.358
9 x 2.5 in springform	63.6	11	7.4	1
9 x 3 in tube (3.5 in centre)	54	11.2	7.5	0.849
Two 8 x 2 in rounds	100.5	13.9	9.3	1.58
Two 9 x 2 in rounds	127.2	17.6	11.8	2
Three 6 x 2 in rounds	84.8	11.8	7.9	1.333

Sometimes you have a particular cake recipe in mind but not the pan size called for in the recipe instructions. This is one of the most common problems faced by bakers and the solution involves a single number. You multiply all ingredients by this conversion factor.

When comparing cake pans, do not focus on the width but rather how much batter they can hold. As area increases proportionally to the square of diameter, a pan that is one inch larger in diameter is actually significantly larger. If this point is ignored, the cake may overflow from the oven or become flat and dry when baked.

Calculation:

First, calculate the base area of each cake pan and then divide your pan's area by the one given in the recipe instructions.

\text{factor} = \frac{\text{area of your pan}}{\text{area of the recipe's pan}}

The area depends on the shape.

A_{\text{round}} = \pi \times \left(\frac{d}{2}\right)^{2} \qquad A_{\text{square}} = s^{2} \qquad A_{\text{rectangle}} = L \times W

Bun and angel food cake pans have two diameters because they are a circle with another circle cut out of the middle.

A_{\text{ring}} = \pi \times \left[\left(\frac{D}{2}\right)^{2} - \left(\frac{d_{\text{hole}}}{2}\right)^{2}\right]

Multiply all the ingredients in your recipe by this conversion factor. If the factor is greater than one you will need more dough and if it's less than one you'll use less dough.

Example calculation:

The recipe calls for a 9 inch round pan but you only have an 8 inch round pan.

A_{\text{recipe}} = \pi \times 4.5^{2} = 63.62 \text{ sq in} \qquad A_{\text{yours}} = \pi \times 4^{2} = 50.27 \text{ sq in}

\text{factor} = \frac{50.27}{63.62} = 0.79

So we use 79% of everything. For example, if the recipe calls for 250 grams of flour, we will use 197 grams. If it calls for 300 milliliters of milk, we will use 237 milliliters.

When you reverse the calculation, it does not give the result that you would expect from a subtraction. When changing from an 8" diameter shape to a 9" diameter shape, the conversion factor is 1.27 and not 1.21. The latter is the result when adding back the subtracted value of 21%. To calculate the reverse factor, use division instead of subtraction. Dividing 1 by 0.79 gives 1.27, and these two numbers are in the same relationship but from opposite sides.

Why not just cut the diameter in half?

When asked how much a half cake will fit into a pan with a diameter of 9 inches, many people answer with 4.5 inches. This is not correct. The batter that fits in a pan with a diameter of 4.5 inches takes up only one fourth of the volume because area quarters when halved.

The actual diameter of a pan that will hold twice the amount of batter is approximately 6.36 inches.

d_{\text{half}} = \frac{9}{\sqrt{2}} = 6.36 \text{ in}

The same relationship shows that a size change from 8 to 9 may seem like only a small difference but actually requires a 27% increase in batter.

Surface area or volume: The choice that this calculation tool makes unequivocally.

Many common cake pan conversion calculators don't clearly explain what they're actually comparing and it's not just rounding differences.

Most converters only compare the surface area and do not change the depth of the cake. This is a reasonable default setting. Recipes are designed to bake cakes with a certain thickness, and if you keep that thickness, the baking time and texture will be similar. However, there are also converters that take into account the height of the pan and compare the volume. In this case, you fill the pan with the same amount of batter as in the recipe pan, making sure to maintain the corresponding height ratio.

If the depth of the pans is equal then both results are exactly the same so there will be little difference to see but if the depths differ then different results occur. If you replace a 9x2 inch round pan with a rectangular baking pan that has a depth of 1 inch, the area factor changes to 2.36 and the volume factor changes to 1.18 which means in one case or the other the batter will overflow from the pan.

Setting	What is held constant	Use it when
Footprint	The depth of the cake	The default, and correct for almost every swap between normal cake pans.
Capacity	The fraction of the pan that is filled	The two pans are noticeably different heights and you care more about filling the pan properly than about matching the recipe's layer.

How much batter should you put in a cake pan?

All detailed baking instructions say essentially the same thing: you should fill your cake pan to no more than two-thirds full. This calculator uses a default value of "two-thirds," but it can be adjusted.

This is important because the conversion factors alone do not tell you if there will be enough room. If a 9x2 inch round pan is filled two-thirds full, it has a batter height of 1.33 inches. If that same amount of batter were to go into a rectangular pan with sides only 1 inch high, no matter how wide the pan is, the batter would overflow. The fill level tester on this page will help you identify problems before they happen in your oven.

Using too little batter can cause more subtle problems. If the cake layer is significantly thinner than the recipe calls for, it will bake faster, brown more and tend to dry out. For this reason, this calculator flags instances where the filling height is less than about one-third of the pan height.

Using multiple cake pans

Since there is a field for the number, this calculator can answer some questions. In a comparison table of recipe blogs, shapes can only be listed individually to get an answer.

The surface area of a rectangular pan measuring 13 by 9 inches is 117 square inches. The combined surface area of two round pans with a diameter of 9 inches is 127 square inches. If you are using a 13 by 9 pan and a 9 inch round pan for one recipe, the factor is 1.09. This means that a two-layer round cake made from a recipe for a rectangular cake would be slightly thinner. Increasing the batter by about 9% will help correct this.

The same adjustment method can also take into account the opposite cases. To bake a cake with a diameter of 6 inches in three layers, you need three molds. Since each mold has an area of 28.27 square inches, the total area is 84.8 square inches. This is an area that is 33% larger than that of a single mold. Here, "a single mold" refers to a round mold with a diameter of 9 inches.

Common conversion examples:

The following factors are not simple representations of pre-determined values but have been calculated by dividing the area of the desired shape by the area of the shape given in the recipe.

Recipe calls for	You have	Multiply by
8 in round	9 in round	1.27
9 in round	8 in round	0.79
9 in round	6 in round	0.44
8 in round	6 in round	0.56
8 in round	10 in round	1.56
7 in round	9 in round	1.65
9 in round	Two 8 in rounds	1.58
13 x 9 in rectangle	9 in round	0.54
13 x 9 in rectangle	8 in square	0.55
6 in round	7 x 11 in rectangle	2.72
17 cm round	23 cm round	1.83

There are some equivalent relationships that are worth memorizing as they come in handy often. A round shape with a diameter of 9 inches has an area of 63.6 square inches while a square shape with sides of length 8 inches has an area of 64 square inches. As far as the recipe is concerned, these shapes are about the same size so no conversion is needed if you substitute one for the other.

The egg problem

While flour can be scaled up or down as desired, eggs cannot.

If a recipe calls for 3 eggs and you're increasing it by a factor of 1.83, then you'll need 5.49 eggs in theory. It is possible to crack an egg open and weigh out part of it. This method is often used by professionals when baking wedding cakes. If you're only making one cake for a Tuesday night dinner party, you can round the number of eggs up to 5.

In this case however the factor in the recipe no longer changes to 1.83 but becomes 1.67, calculated as 5 divided by 3. If you for example increase flour and sugar with a factor of 1.83 while only increasing the number of eggs with a factor of 1.67, the dough can become drier than stated in the recipe without being noticed. Cakes are very sensitive to the ratio between liquid and dry ingredients.

When you enter the number of eggs on this page, the calculator will process it honestly. It rounds the number of eggs, calculates the factor based on the actual amount of eggs used and adjusts all other ingredients accordingly. Even small corrections can be crucial for whether a cake turns out or is just acceptable.

Adaptation of oven temperature

There is no universal formula for baking time. Tools that suggest such a formula are only estimates. What actually exists is an adjustment guideline.

If the batter is deeper than called for in your recipe, you will need to bake it longer and at a lower temperature. Reduce your oven temperature by about 25 degrees Fahrenheit (F) or 15 degrees Celsius (C), and increase your baking time. If a deep cake is baked at the original temperature, the outside will set before the center has a chance to cook through, resulting in a sunken center.

If the dough is thinner it should be baked at a higher temperature for less time. Increase your oven temperature by about 25 degrees Fahrenheit (F) and start checking much earlier than the recipe calls for. Even doubling the amount of dough does not necessarily double the baking time.

If you want to keep the depth, i.e. the base area stays the same, then the baking time hardly changes. Nevertheless, you should start testing about five minutes earlier, as wide and flat shapes tend to set faster at the edges. Wooden skewers or wooden toothpicks often give a better indication of the state of the cake than any clock. Compared to metal test sticks they allow for a better assessment of the consistency of the raw dough.

Sometimes it's better not to convert at all.

For certain doughs you should use molds designed specifically for them and that doesn't change with any calculation.

Pan	Why it does not swap
Fluted Bundt	Very sweet, wet batters rely on the centre tube to carry heat inwards and support the rise. The fluting also means the pan holds less than its outline suggests, so the geometry over-estimates it.
Angel food and chiffon tube	The batter climbs the ungreased walls as it rises. Move it to a nonstick or a plain round pan and it has nothing to hold on to.
Springform for cheesecake	Cheesecake needs the tall removable sides and usually a water bath. A cake pan of matching area will not release it.
Anything one size step apart	A 20 cm to 22 cm change, or an 8 to 9 inch round, is often not worth the trouble. The cake is a little taller or a little flatter and that is all.

Glass and ceramics do not necessarily need a different size but rather a different attitude. As they retain heat longer than metal, you should lower the oven temperature by 25 degrees Fahrenheit and expect a cooking time that may be about ten minutes longer.

How to measure baking molds correctly:

Measure the inside from edge to edge not the outside frame. Wall thickness or overhangs can add half an inch and on small shapes that half inch can be a significant error in measurement.

For round shapes measure the diameter in the widest part that runs through the center. For rectangular shapes measure two sides. When measuring height place a ruler perpendicular to the work surface and read the measurement up to the top edge of the shape.

The most accurate method is to not use a ruler at all. Simply fill the pan with water and count how many measuring cups it takes. This will give you the actual volume including the sloping sides. For decorative pans this is often the only way to get an accurate measurement.

The published capacity listings differ by about a full cup from each other, and for this reason: Geometrically, 6.96 cups fit into an 8 x 2 inch round container; one common reference list says 6 cups, another says 7. The sides of actual containers are sloped so the capacity is slightly less than that of a perfect cylinder in both cases. In addition, each listing measures a different type of container.

This tool is meant to assist with conversions and does not constitute recipe verification. It will show the amount of dough required and whether or not it fits into a pan but cannot guarantee what the end result would be if a particular type of dough were baked in an unapproved pan.

First calculate the area of the shape given in the recipe and the area of your existing pan. Then divide the area of your existing pan by the area of the pan given in the recipe, and multiply that result by each ingredient. The surface area of a round pan is calculated as the area of a circle, so 3.1416, where you halve the diameter and then multiply that result by itself again. The surface area of a rectangular or square pan is found by multiplying length times width. A round pan with a 9 inch diameter has an area of 63.6 square inches while a round pan with an 8 inch diameter has an area of 50.3 square inches. So if you are baking a recipe for a 9 inch pan in an 8 inch pan, then you will need to increase all the ingredients by a factor of 0.79. If the recipe includes eggs, round up the calculated number of eggs to the nearest whole egg and adjust all other ingredients accordingly.

Cake Pan Calculator

The pan your recipe calls for

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