What is letterboxing?

Letterboxing adds horizontal black bars to the top and bottom of a frame when the source video is wider than the target container. The bars fill the unused vertical space after the video is scaled to fit the container width.

What is pillarboxing?

Pillarboxing adds vertical black bars to the left and right of a frame when the source video is taller (or narrower) than the target container. The bars fill the unused horizontal space after the video is scaled to fit the container height.

How are bar sizes calculated?

The calculator scales the source video to the maximum size that fits inside the target frame while preserving the original aspect ratio. Bar size is (frame dimension minus scaled dimension) divided by two, giving the bar on each side.

Can I enter non-standard aspect ratios?

Yes. Enter any width:height values in the custom fields. Decimal values like 2.39:1 are also supported.

What if the aspect ratios match?

When source and target ratios are identical, no bars are needed. The video fills the frame exactly and bar sizes are zero.

Aspect Ratio Letterbox Calculator

Name: Aspect Ratio Letterbox Calculator
Availability: InStock
Author: Nham Vu

Enter source and target aspect ratios to instantly see letterbox or pillarbox bar sizes and scaled video dimensions.

Input

Source Video Aspect Ratio

Presets:

Target Frame Aspect Ratio

Presets:

Target Frame Size (pixels)

Width

Height

Edit either field — the other updates automatically from the target ratio.

Preview

Source

Letterbox (horizontal bars)

Results

Bar type

—

Frame size

—

Scaled video size

—

Top bar

—

Bottom bar

—

Scale factor

—

Bar coverage

—

FFmpeg pad filter

—

Summary

Enter source and target aspect ratios to instantly see letterbox or pillarbox bar sizes and scaled video dimensions.

How it works

Enter the source video aspect ratio (e.g. 16:9) or pick a preset.
Enter the target frame aspect ratio (e.g. 4:3) or pick a preset.
Specify the target frame width or height in pixels.
The calculator shows scaled video dimensions and exact bar sizes.
Switch between letterbox (horizontal bars) and pillarbox (vertical bars) results automatically.

Use cases

Determine black bar sizes before exporting a widescreen video to a 4:3 broadcast frame.
Verify pillarbox dimensions when placing a 9:16 vertical clip into a 16:9 timeline.
Calculate safe areas for overlays on letterboxed content.
Plan crop or pad settings in FFmpeg, Premiere Pro, or DaVinci Resolve.
Check whether a cinematic 2.39:1 source fits within a 1.85:1 theatrical frame.
Understand scaling math when mixing aspect ratios in multi-camera edits.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu