Beam Size Calculator (BSC)

Project Optional. Used for the PDF report header.

Project name Prepared by Display units

Screen

Calculation based on Value (mm) Aspect ratio (W : H) Height from floor (mm) Derived dimensions

Projector and lens

Seed database, 2026-05-17 — entries marked (unverified) have estimated specs. See shared/databases/projectors.json.

Projector Lens Lens diameter (mm) Shift range (V / H)

Positions

Throw distance (mm) Lens centre to screen plane. Projector lens centre height (mm) Porthole distance from lens (mm) Lens to porthole plane (small, typically 100–500 mm).

Porthole

Width (mm) Height (mm) Centre height from floor (mm)

Calculation mode

Mode

Results

Pick a projector to begin.

Configuration

Computed

How to read this Background on the inputs, drawings, and verdict.

The three modes

This calculator answers one of three questions. Mode A, verify fit, is the default: you have everything and want to know whether it fits. Mode B gives the smallest aperture the beam clears at your positions. Mode C gives the range of lens-centre heights that keep the beam clean through a fixed porthole.

Fit verdict tiers

Clean = all margins ≥ 10 mm. Tight = all margins ≥ 0 but at least one < 10 mm. Partial clip = at least one margin between −20 mm and 0. Fail = at least one margin worse than −20 mm.

Lens shift

When the lens centre is off the screen’s vertical centreline, the projector must shift the image vertically to land it centred. That is a derived requirement, expressed as a fraction of image height. If it exceeds the lens’s published shift range, the projector has to be repositioned. This reports the geometric requirement.