So about a year ago I came up with is a basic conversion formula that tells you by which factor you should multiply the ingredients the original recipe calls for in order to end up with exactly the right amount of batter for your cake pan of choice. Unfortunately, it wasn’t as handy as I’d hoped. As it turns out, I did not only post the wrong formula (not very practical), some of my readers pointed out that there is a much easier formula!

Seriously guys, even those of us who suck at math (like me) can do this!

So let’s dive right in!

**When you don’t have the right size cake pan**

Imagine being in your kitchen, ready to bake an awesome cake. The first thing you do is turn on your oven and read through the recipe (because we all do that, right?). Say the recipe you want to make calls for an 8-inch springform pan, and all you have is a 9-inch springform pan. Or, even worse, you don’t even *have* a springform pan and all you have is a regular round 9-inch cake pan. Or, you have an 8-inch cake pan, a 10-inch cake pan and even a 12-inch cake pan, but not a 7-inch cake pan!

It’s the worst! Especially if you’re halfway through a recipe…

So what do you do when this happens? Well, you may find yourself surfing the world wide web in order to find out if you can use one of your other pans. Usually, what you’ll find is something like this:

Pan Size | Volume | or… | Pan Size | Volume |
---|---|---|---|---|

6 x 2 inches | 4 cups | 18 x 5 centimeters | 1280 mls | |

8 x 2 inches | 6 cups | 20 x 5 centimeters | 1570 mls | |

9 x 2 inches | 8 cups | 22 x 5 centimeters | 1900 mls |

Yeah… So not helpful! I don’t need to know how much water goes into a 6-inch pan! I need to know if I can use one of the pans I already have instead of the pan the recipe calls for!

Enter: the Round Cake Pan Conversion Formula!

**Why You Need The Round Cake Pan Conversion Formula**

If you were to use a smaller cake pan that the recipe calls for, you would quickly find out that the amount of batter the recipe makes is too much for your smaller pan. Best case scenario? You realize this before the pan is in the oven and decide not to pour all the batter in. That could happen.

Another thing that could happen is: you pour all the batter in your cake pan only to find out that, once it’s time to pull the cake out of the oven, it isn’t done yet. You decide to give the cake another few minutes in the oven, which eventually leads to a done cake with a burned top. Not ideal…

And the worst case scenario? You pour all the batter in, place the cake in the oven and go about your business. Forty minutes later you’re scraping blackened bits of cake from the bottom of your oven, because the batter has spilled over the edges of your cake pan…

Truth be told, using a smaller cake pan isn’t the end of the world, especially if you know what you’re doing. I make larger batches of cake batter all the time and use them to make smaller cakes. After all, experienced bakers know to only fill a cake pan halfway to two-thirds of the way up with batter. And having some leftover batter usually isn’t a problem. Not in this house, anyway…

No, it gets tricky when you only have a slightly larger pan at your disposal. Sure, you could double the recipe, but usually that means that you will have a lot of leftover batter. And while I like a little leftover cake batter, I don’t like having an entire bowl of the stuff… I can’t just throw it away, but eating it all seems a little excessive… So does eating an entire batch of cupcakes made with leftover batter…

**The Round Cake Pan Conversion Formula in Centimeters and Inches**

Like I said: with this formula, you can adjust the original recipe to fit your cake pan of choice. Just keep in mind, this formula only changes the cake’s diameter, not its height! If you want a taller or thinner cake, this formula won’t help you much.

**Step 1: start by determining the radius of the pan the recipe calls for:
**

(diameter of cake pan in centimeters or inches )/ 2 = radius

So, for a 18-cm cake pan:

18/2 = 9 cm –> radius is 9 cm

For a 7-inch cake pan:

7/2 = 3.5 inches –> radius is 3.5 inches

**Step 2: determine the radius of the pan you want to use:**

Again: (diameter of cake pan in centimeters or inches )/ 2 = radius

If you want to use a 20-cm cake pan:

20/2 = 10 cm –> radius is 10 cm

If you want to use an 8-inch cake pan:

8/2 = 4 inches –> radius is 4 inches

**Step 3: use the new round cake pan conversion formula to determine the factor with which you need to multiply the ingredients in the recipe**

Round cake pan conversion formula:

**(radius x radius of the pan you’re using)/ (radius x radius of the pan the recipe calls for) = factor**

So, in centimeters:

(10×10)/(9×9) = 1.234

If the recipe calls for a 18-cm cake pan and you want to use a 20-cm cake pan, the factor with which you need to multiply the ingredients the recipe calls for is 1.234.

And in inches:

(4×4)/(3,5×3.5) = 1.306

If the recipe calls for a 7-inch cake pan and you want to use a 8-inch cake pan, the factor with which you need to multiply the ingredients the recipe calls for is 1.306.

**Step 4: once you’ve calculated the factor by which you should multiply the ingredients, calculate the amount of ingredient’s you’ll need:**

The recipe may call for the following ingredients:

– 4 eggs

– 200g (or 1 cup) of sugar

– 1 teaspoon of vanilla extract

– 480ml (or 2 cups) of milk

For centimeters:

4 (eggs) x 1.234 = 4.936 eggs **–> 5 eggs**

200 (grams of sugar) x 1.234 = 246.8 grams of sugar **–> 250g of sugar**

1 teaspoon (vanilla extract) x 1.234 = 1.234 teaspoon of vanilla extract **–> 1¼ teaspoon vanilla extract**

480 (ml of milk) x 1.234 = 592.32 ml of milk **–>590ml milk**

For inches, bearing in mind that 1 cup equals 240ml:

4 (eggs) x 1.306 = 5.224 eggs **–> 5 eggs**

240ml (of sugar) x 1.306= 313.44 ml of sugar **–> ****1¼ cup + 1 tablespoon sugar**

5 (ml vanilla extract) x 1.306 = 6.53 ml **–> ****1¼ teaspoon vanilla extract **

480 (ml of milk) x 1.306 =626.88 ml **–> 2½ cups + 2 tablespoons of milk**

Of course, if you measure by volume rather than weight, you need to be aware of the following:

CUPS | VOLUME |

1 cup | 240ml |

½ cup | 120ml |

⅓ cup | 80ml |

¼ cup | 60ml |

SPOONS | VOLUME |

1 tablespoon | 15ml |

1 teaspoon | 5ml |

½ teaspoon | 2.5ml |

¼ teaspoon | 1.25ml |

**So, just to recap:**

**Step 1: start by determining the radius of the pan the recipe calls for:
**(diameter of cake pan in centimeters or inches )/ 2 = radius

**Step 2: determine the radius of the pan you want to use:
**Again: (diameter of cake pan in centimeters or inches )/ 2 = radius

**Step 3: use the new round cake pan conversion formula to determine the factor with which you need to multiply the ingredients in the recipe using the round cake pan conversion formula:
**(radius x radius of the pan you’re using)/ (radius x radius of the pan the recipe calls for) = factor

**Step 4: use this factor to calculate the amount of ingredient’s you’ll need:
**factor x ingredients = right amount of ingredients for your pan

That’s it! Isn’t that easy??? This way, you can turn a recipe that makes a tiny 13-cm/5-inch cake into a huge wedding cake! Just calculate the factor by which you need to multiply the ingredients! And don’t worry too much if the amount of ingredients you need is a bit odd, like 388ml or something. Trust me, 390ml will do fine!

Oh, and the best part? This method works for regular cake pans and springform pans! Just don’t forget to use your head before pouring a batter into a springform pan. The batter can’t be too runny! Oh, and baking a cheesecake in a regular cake pan doesn’t sound like a good idea to me either, but apart from that, this method works beautifully!

Thanks Arielle and Boelo for letting me know that the last formula was wrong and for showing me an easier method

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Dee says

I’ve been looking for this formula. This is the most practical and easy way to convert cake pans. Thanks for sharing. 😀

The Tough Cookie says

You’re welcome, Dee

Merc says

But, what if not even the diamters aren’t the same, but the height as well?

Fx.

The receipe calls for a 16×10 cm round form, but I have a 25×7 cm round form?

The Tough Cookie says

Hi Merc, I’m sorry but I don’t really understand your question. Do you want to know how the use of this formula affects the height of the cake?

Vivi says

So the point i want to asking is can recipe that call for using 7inch pan being bake in 10inch pan?

The Tough Cookie says

I’m not sure how to answer this… Are you asking me if you can use this formula to change a recipe or whether you can try baking a recipe for a 7-inch pan in a 10-inch pan?

Fiona says

How would you calculate the baking time if you were to convert a large cake recipe to a smaller one? (IE: using a 6-inch cake recipe with 40 minute baking time to a 4 inch?

The Tough Cookie says

Hi Fiona, if you’ve been baking for a while, you may have noticed that baking time is never set in stone. When I convert a cake recipe, I usually do a test run, and keep an eye out on the cake to determine whether it’s done or not. If I were you, I’d start checking the cake after about 15-20 minutes. If it looks done through the oven door (not too pale or undercooked), open the oven door and gently press the top of the cake. If it springs back, insert a cake tester in the center of the cake. If it comes out clean, the cake should be done. I wish I also had a formula to convert baking times, but I hope this helps too 😉

garima says

Hey, how do i adjust the baking time or temperature if i switch from a 8 inch tound cake pan to a 9 inch round pan.

The Tough Cookie says

Hi Garima, if you convert a recipe to make a cake larger, the cake will need more time in the oven. Unfortunately I can’t tell you exactly how long the cake should bake, as I don’t have a formula to convert baking times. However, I’d say do a test run and start checking the cake after it’s been in the oven long enough to for an 8-inch cake. First look through the oven door. If the cake looks undercooked, give it about 10 more minutes. If the cake looks about done, open the oven door and test it for doneness by lightly pressing down on the top. If the cake is done, the top of the cake should spring back. You can also test for doneness by inserting a cake tester into the center of the cake. If it comes out clean, the cake is done. Hope this helps

Leonela says

Your conversion is very helpful but what if the recipe is in cups? Do I convert it into ml before multiplying by the factor ?

The Tough Cookie says

Hi Leonela, I don’t think you need to convert the cups to ml first. For example, 1 cup x 1.2 = 1.2 cups. 240ml x 1.2 = 288ml, which is 1.2 cups. However, if you happen to have a kitchen scale and feel like converting to mls or grams (especially when working with dry ingredients) I always recommend using a scale, because by multiplying the ingredients you may end up with weird amounts that are difficult to measure in cups, such as the above mentioned 1.2 cups. Hope this helps!

Crizette Yap says

hello,thanks for sharing its interesting.if the recipe call for 9 round 21/2 inch high and i want to use the smaller pan to 6 or 8 inch pan.how to compute it .should i divide it into 2?thanks!

The Tough Cookie says

Hi Crizette, just use the formula, using 9 inch for the diameter of the ‘called for pan’, and 6 or 8 inch (depending on which one you choose to work with) for the ‘pan you want to use’.

Juliet says

Hi,

Just wanna say thanks a lot for this formula.

And also I see that you’ve been very patient in your replies and really wanting to help everyone. Cheers to that! =)

The Tough Cookie says

Thanks Juliet, I try 😉

Helen says

Brilliant! This post just totally saved my day (and my upcoming tea party). 15cm to 20cm no problem.

Thank you.

The Tough Cookie says

So glad my post was helpful Helen 😀

Luisa says

Hello,

Thanks for the formula, I’ve been looking for something like this for a while… I am slightly confused about how to scale DOWN using the formula, I have a recipe for a 10 inch cake that I want to convert to 8 inch tins, then 6 inch etc down to 4 inches but as I scale down the tins the recipe gets larger because in step 3 : conversion formula the number I divide the original radius of goes up, for example 10 inch to 8 inch in step 3 = 5×5 (25)/4×4 (16) = 1.5625 so my new recipe is 525g / 1.5625 (336g) but for a 6 inch tin it is 525g / 1.11111 (472g). I am not great at maths so sorry for the confusion. Thanks! Luisa

Luisa says

I am sorry to waste your time, I was doing it wrong, it works great!!

The Tough Cookie says

Haha, just read this now 😉 Glad you figured it out!

The Tough Cookie says

Hi Luisa, I think you’ve misread the formula a bit. You want to convert a 10-inch cake recipe to an 8-inch cake recipe, right? In that case, you need to use the following formula: (4×4)/(5×5) = 0.64. The recipe you have calls for a 10-inch recipe, but the pan you want to use is an 8-inch 😉

So, for the 8-inch cake, multiply the ingredients for the 10-inch cake with

0.64.6-inch cake: (3×3)/(5×5)=

0.364-inch cake: (2×2)/(5/5)=

0.16Hope this helps!

Pete says

It’s worth pointing out that this formula will result in a cake of the same height. No big deal when most conversions will be for fairly similar sized tins (eg 23cm to 20cm – 9” to 8”). However, for larger differentials or circumstances where you need or want to maintain the relative proportions (height to width), the factor should be a ratio of the cubes (eg 10^3 divided by 11.5^3). Without taking this into account, scaling from, say, 30cm to 18cm (12” to 7”) would produce a cake that looks too tall for its size.

Helen Peatling says

Hi, I want to make a rectangle cake which should be cooked in a rectangle tin size 28cm x18cm, but I only have a 32cm x 22cm rectangle tin. Can you please tell me how to do this. I’m only a home cook and am not understanding the chart. It’s not your fault it’s me. Can you please tell me the adjustments to the recipe please, Helen.

The Tough Cookie says

Hi Helen, sorry for the late reply but your comment got lost Have you worked out the factor yet?

Diana Mascarenhas says

Hi just wanted to say a big thank you regarding this formula it really worked out so well and the make came out really well.just a few questions though

If the calculation on the eggs comes to about 2.458 do I use 2 eggs only or 3

And if it’s measurement is spoon wise then how do I do the calculation coz I got a bit confused on the baking powder as the recipe reads 1/4tsp and the calculation says 1.234.

Hope I am making myself clear.

Awaiting for your reply thanks

The Tough Cookie says

Hi Diana, so sorry for the late reply. Your comment got lost

If the calculations say 2.458 eggs, you can use 2.5 eggs. I’m personally okay with using half an egg, but I won’t crack an extra egg for a third or fourth of an egg, except if it’s a particularly finicky recipe (macarons!).

If you measure in spoons, it’s easiest if you calculate in mls. For example, 1/4 of a teaspoon is 1.25mls. If you multiply that with your calculated factor, you should end up with an amount x in mls, because you’re thinking in mls, not teaspoons. You then simply convert the needed mms back to spoons again. Hope this helps!

Sumin says

Hello this is such a useful tip! I have a quick question. If I decide to bake in a smaller pan, does that only change the baking time and not the temperature?

The Tough Cookie says

Yes Sumin, only baking time

Kara F says

This was very helpful and worked great! Just for the sake of simplicity, I want to mention that you can actually cut out a step in your calculations. Your factor, which is a ratio of the radii squared, will be exactly the same as simply taking the ratio of the diameters squared. As illustration, if we want to convert a recipe that calls for an 8 in pan to enough batter for a 9 in pan, following your equation, we would first find the radii (8 in diameter = 4 in radius; 9 in diameter= 4.5 in radius), then plug in : (4.5×4.5)/(4×4) = 1.266 as our factor. Alternatively, we can plug in diameters instead and get the same factor: (9×9)/(8×8)= 1.266.

Of course, either way works! I just wanted to mention this in case the minimizing calculations is helpful for people.

Thanks again!

The Tough Cookie says

Hi Kara, thanks so much for sharing this! I’m not really a math genius 😉

patti says

Hi, thank you for this helpful formula! I’m not a baker but I am trying to figure out if I can get away with using use a regular 9″ round pan instead of the recipe’s 8″ springform, and I’ve calculated the ratio at 1.125. I see in the comments above you mentioned that “2.45 eggs” could be rounded to 2.5 — but I have two questions… My calculations will increase the number of eggs from 6 to 6.75 — so I should NOT round up to 7 eggs, is that correct? And if I need to use “precisely” 6.75 (or even 6.5), how would I go about estimating 3/4 (or 1/2) of an egg? (The original recipe calls for 3 ingredients — 6 eggs, 1/2 cup butter, and 1 pound chocolate — that’s it… Is it ok to “eyeball” estimate it”, or is it important enough to warrant using my kitchen scale? Thanks!

The Tough Cookie says

Hi Patti, I’m so glad you like this formula! It sounds like the recipe you’re trying to make is pretty casual (are you making a flourless chocolate cake, by any chance?) so in this case I’d just eyeball the 3/4 of an egg. Whisk one egg, than use three quarters of it for your recipe.

Ed says

Thanks so, so much, was wondering how I could make a 8inch birthday cake with a 9inch bowl!! Thanks a lot- very useful. Can I just ask- how the hell did you work it out!?!?

The Tough Cookie says

I’m so glad I could be of help, Ed! 😀 And yeah, it took me a few headaches to get the formula right…

Kerrima says

This is great stuff, very helpful. I’m trying to estimate some costs and working out how to covert a regular cake into a 3 tier and cost it was a nightmare before I found this. Brilliant, thanks!

The Tough Cookie says

Glad you like the post Kerrima!