A 'Number 'cake mould

This is the caje mould (if succede in posting it)

Why not make up a batch of batter and see how it goes. If it’s not enough, make some more. If it’s too much, throw it away or make something else

Would filling the mould with water then measuring how much it took to fill it give you an idea?

thanks petra , that is of course the very sensible thing to do to make quite a lot fill the thing to three-quarters and then fill cupcake moulds with leftovers.
Just trying to work out just how much I dare to go to, maybe a version of the 666 recipe and go 888.

Find a tin you usually use for cakes and fill that with water up to to the level you usually fill it with cake mix.

If it has a detachable base put a plastic bag in it first.
Measure the millilitres of water (representing cake mix).

Now measure how many millilitres of water your number 1 needs to fill up to "cake mix level"

From comparing the millilitres of the number tin to the ordinary one you will see how much cake mix to make.

It may be half as much, twice as much or whatever but you will easily see approximately how much you need.

This is what I'd do.

Good luck.

thank you NotSpaghetti, again sensible idea.

Fill the mould with water and measure the amount, easy peasy.

Fill mould with water then measure/weigh the water. From there you should be able to work out the sponge batter volume.

and please, no Betty Crocker. A basic sponge is very easy to make (look up Delia Smith) even for a beginner .

Please send photos when it’s finished, enjoy a good cake photo.

Thanks for the advice, the water thing was of course very sensible. So far I've made one of the zeros as a fruit cake (Mary Berry) and have made fondant butterflies and flowers and a little Grandma. My M-i-L will be 100 so it needs to be pretty.

and some of the decorations...will do more the day before once the fondant is on.

Looks like it will be a wonderful cake. Beautiful decorations.

https://www.gransnet.com/uploads/talk/202510/medium-1h7qj0-1000036727.jpg https://www.gransnet.com/uploads/talk/202510/medium-b5jm45-1000036726.jpg https://www.gransnet.com/uploads/talk/202510/medium-g6wift-1000036725.jpg

Cakes are done, will post photos of all assembled as tomorrow is her party. The card from the King has arrived all set now.

i have to add the tiny grandma and a a diamente '100'

I love Grandma, she's wonderful!