Exactly what is the proper way to calculate water lift?

Let's say I have a 10' total rise and my pump is a 300gph.

How do I figure out the new gph?
There must be a simple/ standard formula.

BTW, the information and friendliness in this ng is rather unique. The posts
& info has helped me immensely, even though I had to drain & "fix" my
mistakes twice. The pond looks wicked awesome now, thanks to info from
people in here.
--
The~Doofie~Man ©
"LET ME SEE YOUR CIGARETTE LIGHTERS!!!!!"
Putting the fun back in FUNeral!!
http://www.geocities.com/doof70/index.html