How do i know how many servings per cake? Is there a website that would tell me how many servings depending on the different size cake pans??

There are several sites that offer help on servings.
Our own IndyDebi has a chart ....
Wilton.com has one. Many of us base our pricing on these #s but there cutting chart is thumbs down!
Earlene Moore also has a chart. Her serving sizes are larger than the industry standard of 1x2x4.

The you can also figure out your self what each size pan serves by drawing a size of each out of paper (use newspaper for larger ones) ; mark off the sizes and count Sq & sheets are easy to figure as single layers are cut into 2x2x2 servings so if the sheet is say 9x13 you would multiply 4x6 to find it serves 24.

It's the Cook's Dream website then scroll to the bottom to "batter data"

http://cooksdream.com/Merchant2/merchant.mvc?Store_Code=C&Screen=batter_data

Wilton has one but they have it deeply embedded into their website. So this one is easier to get to and I really like the Ultimate Baker, Cook's Dream boys. They've been good to me.

Here's the wilton chart: http://www.wilton.com/wedding/wedding-cakes/wedding-cake-data.cfm

Here's my website page showing you how to cut a cake to achieve the wilton servings: http://cateritsimple.com/_wsn/page10.html

Here's what a 1x2x4 piece of cake looks like: http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1156785