Calculating Attenuation

[NWMushroom]

I'd appreciate some help figuring out attenuation on a recent brew.

My opening gravity was 1.073 so I used two packets of rehydrated Safale 05. I understand the attenuation of this yeast is around 73-77%.

Am I right in assuming I should get down to a final gravity of around 1.018? Does the fact I used two packets influence the FG?

 

[BBL_Brewer]

That's correct. The FG should be around 1.018 if the yeast attenuates as advertised. Pitching two packets of yeast won't negatively affect your FG. In fact it should do nothing but help.