How bright will this projector and screen combination be?
Brightness depends on usable lumens, screen area and gain. Published lumens alone are not enough: label the entered value, reserve loss/headroom, and measure the installed image before deciding.
Method
Screen width and height come from diagonal and aspect ratio. fL = usable lumens × gain ÷ area (ft²); nits = fL × 3.426. Reserve is an editable planning assumption.
Important limitation
Brightness does not guarantee contrast, HDR quality, black level or viewing suitability. Use a meter and exact product documents.