Put this here because I think tuners would have a better handle on this.

I want to convert AFGS to CFM. How much does one cubic foot of air weigh (in grams)?

 

That depends on the temperature, pressure, and to some degree, humidity.

One cubic foot of air at standard temperature and pressure assuming average composition weighs approximately 0.0807 lbs.

For non-standard temp and pressure calculate using this formula.

Wt = (1.325) x (B) / (T) + (459.2)

where:
1. Wt stands for weight
2. B stands for barometric pressure
3. T stands for temperature