Aspect Ratio Calculator
Use RatioForge as a fast aspect ratio calculator for images, videos, designs and screen sizes. Enter a width and height to simplify the ratio, or choose a ratio such as 16:9, 9:16, 4:5 or 1:1 and calculate the missing dimension.
Calculator
Common aspect ratios
| Size / ratio | Label | Use-case |
|---|---|---|
| 16:9 | 1920×1080 | YouTube, TVs, monitors, presentations |
| 9:16 | 1080×1920 | TikTok, Reels, Stories, Shorts |
| 4:5 | 1080×1350 | Instagram portrait feed posts |
| 1:1 | 1080×1080 | Square posts, profile pictures, icons |
| 21:9 | 2560×1080 | Ultrawide monitors and cinematic layouts |
Formula
- To find height: height = width × ratio height ÷ ratio width
- To find width: width = height × ratio width ÷ ratio height
- To simplify a ratio: divide width and height by their greatest common divisor.
When to use an aspect ratio calculator
The calculator is useful before exporting a YouTube video, cropping an Instagram post, sizing a website image, preparing a presentation slide or checking an existing file. It works with pixels and proportional dimensions, so the same logic applies whether you are planning a 1920×1080 video, a 1080×1350 portrait image or a custom web container.
Aspect ratio describes the shape of a rectangle, not its quality or file size. A small 1280×720 image and a large 3840×2160 video are both 16:9 because they reduce to the same proportion. That is why ratio comes before resolution: choose the shape first, then choose how many pixels you need.
For content work, the wrong ratio usually creates visible problems. A horizontal image may get cropped in a vertical Story, a square logo can look padded inside a widescreen video, and a web hero image may shift awkwardly across breakpoints. Calculating the ratio before exporting avoids stretching, black bars and accidental crops.
Some visitors only need the missing height for a 1200px-wide image; others want to understand why their video has black bars or why two files with different pixel counts can share one ratio. Calculate and copy your result above, then move into a more specific calculator below when you know your destination platform.
Frequently asked questions
Related calculators and guides
Popular calculators for specific ratios and platforms:
- 16:9 aspect ratio calculator — widescreen dimensions for HD, 4K and YouTube
- 9:16 aspect ratio calculator — vertical video for TikTok, Reels, Stories and Shorts
- Instagram aspect ratio calculator — posts, Reels and Stories placements
- Social media image sizes — recommended dimensions per platform
- Aspect ratios explained — what 16:9, 4:3 and 1:1 actually mean