Victoria Sponge recipe for 20cm square cake tin?

[taffetawitchescat]

I am making a football pitch birthday cake on Thursday for DS's 7th birthday and am using a 20cm square cake tin. I made this delicious Victoria Sponge for DD's birthday in the summer and would love to replicate it for a 20cm square cake, however, the only recipes I can find online are for madeira cakes, which isn't what I want.

I know the Vic Sponge cake stands up well to fondant icing and decorations as this is what I did for DD's.

Any ideas how I should adjust quantities/baking temp/baking times? I only have the one tin so I guess I need to make a big one and slice in half horizontally once cold.

Advice really appreciated.

Here are some equivalents:

Round Square
18cm 15cm
20 18
23 20
25 23
28 25
30 28

Failing that, do some maths with area = pi x r x r and then take the square root to convert from square to round.

Thanks tb - I did find a 23cm round Vic Sponge recipe but the prob with Vic Sponge recipes is they all split between two tins, and I'm only using one, so assume because of the greater density would need to cook for a fair bit longer?

This is all well and good, can tell when a cake is done etc but if cooking for longer should I then reduce temperature?

Keep temp the same. My mother used to make a bit of a dip in the centre, so that when it cooked there wouldn't be too big a bump in the middle. If it does have a bump/cracks, you can always use it upside down. Then you'll have a flat top.

If you get the tins you used last time and fill them with water then pour into your 20cm square tin you will get a good idea of how many times bigger it is. I always cook sponges for about 30 mins whatever ize they are.