Chocolate Birthday Cake Calculator

For those times that you need chocolate cake but you can’t find a tin the right size in your cupboard.

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For those times that you need chocolate cake but you can't find a tin the right size in your cupboard.

It seems that there’s a lot of love around for my Chocolate Birthday Cake Recipe and I’ve started to get requests for the quantities to make it in various different shapes and sizes. So far each time I’ve been asked I’ve tapped away in excel to work out what’s needed, but I thought it was about time I sorted out a calculator (just like my vanilla birthday cake calculator) so you can do it yourselves without waiting for me.

All you need to do is to enter your tin dimensions and the number of layers you’d like the cake to have into the boxes and it’ll tell you what you need. I hope you all find it useful…

Round Tin

Square or Rectangular Tin

As with the vanilla version, I’ve not tested the cake in all possible sizes but as long as you don’t stray too far from the original quantities it should still work well.

Cooking times and temperature are the same as in the original recipe. However, if you decide to put a 2-layer cake into one deep tin rather than splitting it into two sandwich tins, you should wait to check it until it has been in the oven for at least 45 minutes (otherwise it’ll sink in the middle).

If you only know your tin measurements in inches, simply multiply them by 2.5 to get the dimensions in centimetres.

If you’d like to use the recipe to make cupcakes instead of one big cake, the quantities for a 20cm round cake with 2 layers will give you enough mixture for 12 cupcakes. They’ll take 25-30 minutes to cook.


  1. Thank you so much for your chocolate cake calculator! I have the same approach to birthdays as you for my two boys. They choose the cake theme and I scour Pinterest for ideas. I need to make a Harry Potter cake next week for my 5 year old’s birthday. I have ordered a 22x32cm rectangular cake tin to make a spell book, but then just couldn’t find a choc cake recipe I trusted. Your calculator is so clever and much appreciated!! Can’t wait for the tin to arrive and have a go!

  2. silly question…..but the buttercream quantities….is that enough for the middle of the cake and around?

    • It should be enough to fill the middle of the cake, cover the top and have a thin layer around the sides.

  3. Wiil be baking a football shirt chocolate birthday cake for my grandson in a 39x26cm tin 3cm deep,possible to have mixture.

    • Hi Richard,

      I would use…
      300g flour
      345g margarine
      345g sugar
      6 eggs
      1/2 tsp vanilla extract
      3 tsp milk
      60g cocoa powder
      150g milk chocolate

  4. Hi Charlotte!
    I have only recently come across your website and I made your chocolate cake recipe and it was a massive success- thank you! I wanted to ask your opinion on square tints etc. I want to make an oblong cake , as close to the shape of a pint of Guinness as possible! It’s for a birthday cake! I was going to use a rectangular tin but I was conscious of the waste. Do you have any advice as to what I could use? It’s for approx twelve people. Thank you! Paula

  5. Hi Charlotte!
    Thank you!

    • Hi Charlotte- just wanted to let you know I used a rectangular tin as you suggested and it was absolutely fine. Such a lovely cake! I’m hoping to try your vanilla one in similar sizes I also used medium eggs and it didn’t seem dry but I might try with large eggs as well- do you think it would make much difference? Thank you again for this recipe- it is really lovely!

      • Charlotte Oates

        I usually use large for this one but I have used medium if I’ve not got any large in and it’s always turned out fine.

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