I have a cake order for a 3 tier wedding cake for 125 people. The customer is asking me what size pans I am going to use, and I don't even know. I've seen a couple sizing charts, is there anyone that has acually done a cake that knows for certain that it will feed 125 people, I do NOt want to run out of cake

A typical serving is 2 x 1 x 4 (height) inches. For a square cake a 8, 10, 12 inch pans would yield 154 servings. For a round cake a 6, 8, 10, 12 inch pans would yield 132 servings (as per the charts I use). I also provide the client with a cutting chart (for the caterer to use) and say the following in my contract: "The number of servings stated in this contract is based on a cake cutting diagram provided. Please inform your caterer/server to cut each slice to the size mentioned in the diagram if you wish to have the correct number of servings."

wilton has some good serving size charts on their site

I just did a round cake for 125. I used 6-10-14. It was for a friend and I was there. It was plenty.

http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm

A 14" x 10" x 6" yields 128 servings, but they'd need to serve the top anniversary tier.

That you so much...was the 14, 10 and 6 2 layers or 3? Also I called the catering company and they said they would follow the wilton serving size.

Wilton is the only chart to use. There's no need to even look at another chart.

I use the 6/10/14 for 130 servings so that should be fine.

Standard wedding cake height is 4" per tier, so however many layers you stack, they should end up 4" tall after being iced