I tried to figure this out before hand. Doesn't work.
I bought & mounted the Epson 6050 at 16' 6" throw. My wife & I then spent a few months watching movies on a dark gray wall. Seating distance 11'. Tried different sizes and aspect ratios. Wound up with a 130" wide, 149" diagonal 16:9 Seymour XD with masking panels. We went back and forth many times over what was too big or too small. One day we'd say the large size was good; next day, it was too big with different video material.
The point is---try before you buy. There is no other way to know what you'll like. The saying is: you date your projector and you marry your screen.
Epson Pro Cinema 6050, Seymour Center Stage XD 130"w 150"d 16:9, Onkyo DX-C390 Six-Disk CD Changer
Triad Silver Speakers (11 in a 7.2.4 configuration), 2 JTR 118HT Subwoofers
Yamaha CX-A5200 11 Channel Processor, Monoprice Monolith 11 Channel Amplifier
Panasonic DP-UB820 UHD Blu-ray, Sony BDX-BP57 BD/SACD, Harmony Elite Remote, 10 Seats