How many wall 20 amp outlets can I run on a20 amp breaker or what is the math to this.

If this is a residential situation, there is no limit to the # of outlets. The critical thing is what load are you going to put on the system. You could overload a circuit with 1 duplex outlet if you plugged in 2 1500 watt frying pans. I do not like to put more than 8-10 outlets on a single 20amp breaker. You never know what people will plug into them. If you are running out of breaker space, dedicate 2 breakers to a subpanel and start over.

Dee,

Please do not add to a 3 year old post.

As to your question a 20 amp circuit at a full load can support, residential code does not give any limit.

Commercial is 10 duplex outlets per 20 amp breaker. I use this amount on any residential electrical work I do. Here's the math:

20A X 120V = 2400 VA (volt/amps)

Since you are going to use a multi outlet branch circuit you can only load the circuit to 80%

2400VA X .8 = 1920 VA.

Now for the final step, the typical load for each double receptacle is 180 VA, so the yield is 10.

1920VA / 180VA = 10.6 (I round down to 10)

As I said earlier this is more for commercial installations.