I am making a 3 layer 10" round sponge cake filled with buttercream and decorated with the vertical pleat/ruffle type buttercream decoration.  I know this kind of decor takes an awful lot of buttercream, but I wish I could find somewhere that helps you work it out exactly.  When I have done this in the past I always seem to make too little and end up having to make a dash to the shops to buy more butter and make another batch!  

I am making the classic buttercream - butter, icing sugar, water & vanilla.

Any ideas anyone? Or has anyone made this kind of cake that would know how much I need?

thank you 

Wilton used to have an icing guide for base amounts, perhaps you could check their site.

I've gotten into the habit of making more than enough, as the extra can always be frozen and saved.

(or squished between graham crackers for easy cookies).

AI have that very chart bookmarked. http://www.wilton.com/cakes/making-cakes/baking-party-cake-2-inch-pans.cfm

AAlso, maybe you could try doing one ruffle as a trial and see how much it takes? Then just estimate how many of that size you will need. I'm not sure if you are using the Wilton recipe, but 1c fat plus 4 c sugar makes about 3-31/2 c of icing.

Thank you all very much - had been trying to find that link for ages!!  I don't have time for a trial run, but at least once I have done this one I will know for next time 

AAs far as the trial, I just meant do a single ruffle on the back of a cake pan or some wax paper. I know what you mean about time. I usually just wing it, then I'm always nervous I don't have enough of something. So I make way too much instead. But that saved me last week, when I pulled enough frosting out of the freezer to ice 30 cupcakes.

Love that idea of a personal three-ring binder for reference.  I have intentions of doing that myself.  I have so many sticky notes inside cabinet doors, on top of the shortening can, on the backs of recipes, on the fridge, on my dresser (you know, after emptying my pockets).  Never thought of including photos though.  I think I just decided on a new-year's resolution.