Gravel Roof Calculations

Can any one give me an idea how many pound per square foot of loose pea gravel is on a roof?
Roof has between 1/2" to 1" thickness

Also, what would be the calculation per square foot of pea gravel embedded into the Bur roofing? is it half of the loose gravel? 1/4 of the loose gravel?

Thank you for your time and energy in answering my questions.

Roofer Gee

Pea gravel weighs about 2700 lbs per cubic yard or about 100 lbs per cubic foot. “Normal” gravel surfacing is about 4-5 lbs per square foot.

Get yourself a copy of this;http://www.amazon.com/Pocket-Ref-Thomas-J-Glover/dp/1885071000 and a calculator.