Note: I am not asking about the yield of brewed coffee.
Edit: I'm asking how many cups (dry measure) of grounds are in a 1lb bag of ground coffee? Or does it vary by the type of coffee?
The well-known recipe for the ground coffee to coffee beverage ratio is around 1:20.
One pound is equivalent of 453.6 grams. Therefore; you may expect to have 9072 grams of brewed beverage. When you assume that a cm3 coffee beverage is around 1 grams, yo should have a bit more than 9 liters of beverage. Again, this makes around 320 oz. beverage. If you assume that your cups are 10 oz, you should end up with 32 cups of beverage from 1 pound of ground coffee.
I admit that, using such a unit system makes it way harder than stating "1 kg coffee ends up two hundred 100 ml cups", at once.
(Updated after Paul's comment)
The solution is simpler as it depends solely on the density of coffee. Still, we may require a series of unit conversions.
The density of ground coffee is around 0.32 gr/cm3. This means, 453.6 grams (one pound) of coffee has a volume around 1.42 l. This volume is roughly 50 oz. Finally, a cup is 8 to 12 oz, let's say 10 oz on average. Therefore, a pound of coffee should be more or less 5 cups of coffee.
Note: This density is for ground beans. Green coffee beans has a density around 0.56 gr/cm3.
There are far two many variables for a definitive answer. All of the following will matter: exact type (and possibly batch) of bean, roast grade, grind, degree of compression in the cup, even the humidity on the day you measure. The biggest factors will be grind, bean, and roast - assuming you don't try to "settle" the coffee in the measuring cup.
For what it's worth, it usually is possible to fit ground beans in the same bag that held the whole beans before grinding, with a little shaking to settle the grounds. Assuming you have a practical problem to solve, that might solve it.