Help!!! Cake tin sizing for birthday cake

[Queazy]

Right I'm making my dd's doll cake. I'm not a baker. I'm an idiot. I should have bought it

I'm using a Nigella choc cake recipe I know and love, but it says to bake in two 20cm cake tins. I want to use a large 23cm tin and a 2 litre Pyrex dish to make the doll. I have no idea how to roughly work out the amount of mixture I need. Two of Nigella's recipe or more?!?! 23cm is obviously bigger, but I plan to slice in half and ice. The 2l dish is going to be on a wing and a prayer.

Can you smell the fear...

p.s. Thank you in advance to anyone who read to the end and can help

To convert it to the pyrex dish you will need to work out the volume required for the height you want vs the volum of the original tin. This website explains how:

www.cocoandme.com/2010/10/12/cake-pan-size-conversion-the-formula/

For the round - round conversion this is a bit easier to follow

www.cookipedia.co.uk/recipes_wiki/Cake_tin_conversion_charts

For unusual shaped tins I use water. So basically fill with water and tip into a measuring jug

Thank you so much - so, so helpful!

I would say 4 times the normal recipe. If you have extra you can make cupcakes.

I am always surprised at how much more mixture you need for only tin that seems only fractionally smaller! DEFINITELY calculate it online as carefully as you can.