Video Aspect Ratio Calculator
Two Different Problems, One Underlying Ratio
"Aspect ratio" work usually means one of two tasks: reducing a pixel resolution like 1920×1080 down to its simplest ratio form like 16:9, or scaling a resolution up or down to a new width or height while keeping the original proportions intact. Both rely on the same width-to-height relationship, just applied in opposite directions.
The Formulas
Scale: New Height = New Width ÷ (Width ÷ Height)
Scale: New Width = New Height × (Width ÷ Height)
Simplifying finds the greatest common divisor (GCD) of the width and height and divides both by it, producing the smallest whole-number ratio that describes the same proportions — 1920×1080 reduces to 16:9, for instance. Scaling holds the aspect ratio (width ÷ height) constant and solves for whichever dimension you didn't specify.
Common Resolutions and Their Simplified Ratios
| Resolution | Simplified ratio | Common name |
|---|---|---|
| 1920 × 1080 | 16:9 | Full HD widescreen |
| 3840 × 2160 | 16:9 | 4K UHD |
| 1080 × 1920 | 9:16 | Vertical/mobile (Reels, Shorts, TikTok) |
| 1080 × 1080 | 1:1 | Square (social feed) |
| 2048 × 1080 | 256:135 | DCI 2K cinema |
| 1280 × 720 | 16:9 | HD ready |
A resolution can share the same simplified ratio as a very different pixel count — 1080p and 4K are both 16:9, just with four times the total pixels at 4K.
Where This Matters
- Cropping for a different platform — converting a 16:9 landscape video to a 9:16 vertical format for social media requires knowing the new dimensions that preserve as much of the frame as possible.
- Resizing without distortion — scaling only a width or only a height without recalculating the other stretches or squashes the image; solving for the matching dimension avoids that.
- Checking delivery specs — a platform or client spec sheet often names a ratio like 16:9 rather than exact pixel dimensions, so simplifying your resolution confirms it actually matches.
How to Use This Calculator
- Choose a mode: Simplify Width:Height or Scale to New Dimension.
- For Simplify: enter Width and Height in pixels.
- For Scale: enter the original Width and Height, choose whether you're scaling by a new width or new height, then enter that new dimension's value.
- Select Calculate to see the simplified ratio or the scaled resolution.
Related Calculations
Check how a resolution's pixel count multiplies when upscaling with the Video Resolution Upscale Calculator, or work out ideal seating distance for a given screen with the Screen Viewing Distance Calculator.