Aspect Ratio Calculator
Calculate proportional dimensions for images and videos. Enter width, height, or ratio to instantly get the missing value. Common presets: 16:9, 4:3, 1:1, 3:2.
Dimension Calculator (ratio: 16:9)
How to use
- 1 Enter the width and height of your original media (image, video frame, container).
- 2 The tool calculates and displays the simplified aspect ratio (e.g. 16:9).
- 3 Enter a new width to get the proportional height, or enter a new height to get the width.
- 4 Use it for responsive design, video thumbnails, or maintaining proportions when scaling.
Key features
- Calculates the simplified aspect ratio from any width and height
- Computes the missing dimension when width or height changes
- Supports any dimension — pixels, cm, inches, or abstract units
- Useful for responsive images, video embeds, and container sizing
What is Aspect Ratio?
An aspect ratio describes the proportional relationship between width and height, expressed as width:height. A 1920×1080 video and a 640×360 thumbnail both share the 16:9 ratio — scale either dimension by the ratio and the shape stays identical.
Getting aspect ratio right matters whenever you resize, crop, or embed media: a 4:3 image squeezed into a 16:9 frame looks stretched; a 16:9 video in a square container gets letterboxed or clipped. It also shows up in responsive CSS, where the aspect-ratio property (supported in all modern browsers since 2021) lets you define boxes that scale freely.
Common Use Cases
Video resizing and cropping
Calculate the exact new dimensions to resize a video without distortion before exporting.
Responsive image containers
Determine the height needed for a given width (or vice versa) to maintain the same ratio in CSS layouts.
Design asset preparation
Scale a design asset to multiple resolutions (1x, 2x, 3x) while preserving the original proportions.
Social media formats
Convert an image to the exact required ratio for LinkedIn (1.91:1), Instagram Reels (9:16), or Twitter (16:9).
Iframe and embed sizing
Calculate the correct height for a YouTube or Vimeo embed given a known container width.
Game and canvas rendering
Maintain a fixed game canvas ratio when scaling to different screen sizes in HTML5 or CSS.
Common Aspect Ratios
Reference for the formats you'll encounter across video, photo, and UI design.
| Ratio | Example sizes | Typical use |
|---|---|---|
| 16:9 | 1920×1080, 1280×720 | HD video, YouTube, TV, presentations |
| 4:3 | 1024×768, 800×600 | Legacy monitors, old TV, photography |
| 1:1 | 1080×1080, 512×512 | Instagram posts, avatars, thumbnails |
| 3:2 | 1500×1000, 3000×2000 | DSLR photography (standard sensor) |
| 9:16 | 1080×1920, 720×1280 | Reels, TikTok, Shorts, Stories |
| 21:9 | 2560×1080, 3440×1440 | Ultrawide monitors, cinematic video |
Frequently Asked Questions
How do I calculate aspect ratio from width and height?
Divide both the width and the height by their greatest common divisor (GCD). For example, 1920×1080: the GCD of 1920 and 1080 is 120. 1920 ÷ 120 = 16, 1080 ÷ 120 = 9 → 16:9. This tool does that automatically — just enter your width and height and it returns the simplified ratio.
What's the difference between aspect ratio and resolution?
Resolution is the absolute pixel count (width × height), e.g. 1920×1080. Aspect ratio is the proportional relationship between them, e.g. 16:9. Two different resolutions can share the same aspect ratio — 1920×1080 and 640×360 are both 16:9. Knowing this helps when scaling content across devices without distortion.
What are the most common aspect ratios for video?
16:9 is the standard for HD video, YouTube, and TV. 9:16 for vertical formats (TikTok, Reels, Shorts). 4:3 for older TV content and classic photography. 21:9 for ultrawide cinematic video. 1:1 for square social media posts. Each ratio serves a different medium — this calculator makes it easy to convert between them.
How do I calculate height from a known width and aspect ratio?
Divide the width by the first number of the ratio, then multiply by the second. For a width of 800 and a 16:9 ratio: 800 ÷ 16 = 50, then 50 × 9 = 450. The same formula works backwards to find width from height. This tool does both calculations instantly.
What aspect ratio should I use for Instagram, LinkedIn, or Twitter?
Instagram feed: 1:1 (square), 4:5 (portrait), 1.91:1 (landscape).
Instagram Reels / Stories: 9:16.
LinkedIn: 1.91:1 for link previews, 1:1 for profile images, 4:3 for document posts.
Twitter / X: 16:9 for images and cards, 1:1 for profile photos.
YouTube: 16:9 for videos, 1:1 for thumbnails recommended.
Use the tool's "Social Media" presets to get exact sizes instantly.