Projector Throw & Screen Size Calculator

Works out the projected screen width, height and diagonal from a projector’s throw ratio and its distance from the screen. It runs entirely in your browser and shows the working, so you can check every step against your own figures.

How the projector throw & screen size calculator works

A projector’s throw ratio is its distance divided by the image width, so the screen width is simply the distance divided by the throw ratio. For a 16:9 image the height is nine-sixteenths of the width, and the diagonal follows from Pythagoras. The result is quoted as a diagonal in inches, the way screens are sold.

What you enter

Enter the throw ratio and the projector distance; the calculator returns the screen width, height and 16:9 diagonal. Every field is editable, and the result recalculates the moment you change a value.

Reading the result

Check the diagonal against the screen you want, then confirm the projector’s throw-ratio range brackets your figure — zoom lenses give a window of ratios, not a single value, so there is usually room to adjust.

Safe by design

This is pure geometry and acoustics — there is no safety threshold anyone acts on. It plans what you can see and hear, not any electrical or structural work.

Assumptions and limits

This is pure geometry for a 16:9 image on-axis. It ignores lens shift, keystone correction and the small light loss at the edges. A projector mounted off-centre or angled needs its own alignment beyond this size estimate.

Using it with the rest of BuildMetricLab

This calculator is one step in planning the job. Pair it with the related tools in this category and across BuildMetricLab to go from a single figure to a full costed plan — a sizing figure feeds a cost estimate, a cost estimate feeds a project budget, and each result carries straight into the next tool. Every BuildMetricLab tool runs entirely in your browser — no sign-up, nothing sent to a server, and the formula is shown on the page so the maths can be audited.