Circuit "max"

Post Reply | Watch this Post

I've seen this message before, and wished I printed it out (but I didn't). Now I think its "off the board". So, my (repeated) question is:

What is the mathematical formula for figuring out how much I can put on a circuit?

I've got a 20 amp breaker with several light fixtures on it, and I need to know if I can add something else, or, if instead, I need to run a new circuit.

Thanks in advance.