How to I 'up' the ingredients for a 8'' cake receipe using a 9.1/4'' tin

[pelvicflawed]

I'm attempting to make an apple and rasin cake (receipe from the WI book of cakes and biscuits) the receipe is for a 8'' tin but I only have a 91/4'' tin - any ideas what proportion I have to up the ingredients by?? - thanks

I'm not a cake maker but if your tin was 9 1/3 inches it would be 1/6 th bigger than an 8 inch tin, so if you divided the ingredients by six and then added on 1/6th you would have slightly more than you needed.

Divide it by seven and add on a seventh and you will have a bit less.

I think that's right. It's a bit early in the morning!

That sounds good - thanks

Er... Assuming these are circular cake tins and you want the same "depth" of cake in each then I'm not sure that'll work. Don't you need to work out the relative volumes of each tin?

e.g., 8" tin area of bottom of tin will be (pi x r2) or 16 x pi = approx 50.25 inches squared.

For the 9.25 inch tin (radius 4.625 inches) the area will be 67.20 inches squared.

Assuming you wanted, say a 1 inch depth of mixture in each you'd have 50.25 inches cubed and 67.20 inches cubed respectively.

So the 8 inch tin holds approximately 3/4 of the mixture that the 9.25 inch tin holds.

If the tins are square then the calculation will be different - 8 inch tin area will be 64 inches squared, 9.25 inch tin will be 85.56 inches squared so 8 inch tin still holds approx 3/4 of mixture that 9.25 inch tin holds.

The tins might be deeper, but it should be (9.25/8) squared, which is 33.69% more.

So add a third to all the quantities.

Thanks all for you help - will have a go tomorrow and see what we get!!

Ha, sorry I was talking crap. That's the same urge I have if someone asks for directions and I give them even though I don't really know!

Just to let you know have made cake this morning and added 1/3 to each of the ingredients - it looks good (the test will be in the eating when I take it to work tomorrow). Thanks to all of you who offered help.

I'd just make 1 and a half of the mixture and make fairy cakes with the excess...