Searching for the right projector can be a chore. We suggest you to go for reputed brands with good optical zoom abilities.
Though it is counter-intuitive, projector distance from the screen doesn't make any difference in this calculation. It is a flawed advice given by some sellers to sell you a projector with less than required brightness. Please don't fall for it.
This calculator only gives you the brightness required but the optical zoom capability of your projector also matters.