Distances
Five numbers decide where everything goes, and every one of them is taken with a tape measure rather than chosen from a catalog. Each page here has the measurement, the errors that follow from getting it wrong, and the fixes that cost nothing.
Pages with a calculator
Seating Distance
Picture width, viewing angle, and the band on the floor that both ends of the answer mark out.
Distance from the screen
Screen Height
Seated eye height against panel height, and what to do when a stud lands somewhere else.
Screen height from the floor
Projector Throw Distance
Room depth and image width turned into the ratio you take to the manufacturer documentation.
Throw ratio your room needs
Pages without one
These two are settled by a tape measure and a trial position rather than by arithmetic, so no calculator is offered for them.
Mount Clearance
Depth behind the panel, room for the connector, and the arc an arm sweeps across the room.
Speaker Placement
The gap under the picture, the seated ear, and the socket that settles the position.
Limits of a calculator
Every tool on this site prints its formula on the page underneath the result, together with a list of what it does not account for. That list is the important half. A figure produced from three inputs cannot know about the beam over your head, the window behind the seats, or the fact that half the household watches lying down.
Use the number as a starting mark on the floor, then sit at it. Every page here also carries a list of changes that cost nothing, and those settle the room more often than a purchase does.