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Screen Aspect & Letterbox Calculator
Screen width, height and letterbox bars
Updated July 12, 2026 · Live
What this tool does
Works out the width and height of a screen from its diagonal and aspect, and the letterbox bar depth when the content is a different aspect.
Enter the screen diagonal, screen aspect and content aspect; the calculator returns the width, height and letterbox bar depth.
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Formula Used
Works out the width and height of a screen from its diagonal and aspect, and the letterbox bar depth when the content is a different aspect. It runs entirely in your browser and shows the working, so you can check every step against your own figures.
How the screen aspect & letterbox calculator works
From the diagonal and the panel aspect, the width and height come straight from Pythagoras. When the content is wider than the panel — a 2.35:1 film on a 16:9 screen — the image fills the width but not the height, leaving black letterbox bars top and bottom. The tool works out the depth of each bar and the height of the active image.
What you enter
Enter the screen diagonal, screen aspect and content aspect; the calculator returns the width, height and letterbox bar depth. Every field is editable, and the result recalculates the moment you change a value.
Reading the result
The width and height tell you the physical screen; the letterbox bars tell you how much of a 16:9 panel a scope film actually uses. Cinemascope fans sometimes choose a 2.35:1 screen so wide films fill it edge to edge.
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 geometry for a flat screen. It ignores overscan, anamorphic lenses and masking systems. Content aspect also varies shot to shot in some films, so the bars are for the nominal ratio you select.
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.
Sources & methodology
Works out the width and height of a screen from its diagonal and aspect, and the letterbox bar depth when the content is a different aspect. Every result is calculated from the values you enter, all inputs are editable, and no time-sensitive prices or rates are embedded.
Frequently asked questions
Why do films have black bars?
Cinema films are often wider than a 16:9 screen (2.35:1 or 2.40:1). Fitting the width leaves the top and bottom unused, which shows as letterbox bars.
Should I buy a 2.35:1 screen?
If you mostly watch scope films, a 2.35:1 screen lets them fill it with no bars — but 16:9 TV content then gets side bars instead. It is a trade-off.
What aspect is most content?
Broadcast TV and streaming series are mostly 16:9; cinema films are commonly 1.85:1 or 2.35:1. This tool lets you compare any pairing.
Does the diagonal change with aspect?
The diagonal is fixed; the width and height it implies change with the aspect ratio, which is why a 100" 21:9 screen is wider and shorter than a 100" 16:9 one.
Spotted something off?
Calculations or display — let us know.