Aspect Ratio Calculator
This calculator converts image or screen dimensions to aspect ratio, and vice versa. Enter width and height to calculate the simplified ratio (e.g., 16:9). Alternatively, enter one dimension and the aspect ratio to find the missing dimension. Common aspect ratios are displayed in a reference table: 4:3 (traditional), 16:9 (widescreen), 16:10 (computer), 21:9 (ultrawide), 1:1 (square), and 4:5 (vertical). Aspect ratio matters for video production, screen design, social media content, and photography. Knowing the aspect ratio ensures your content displays correctly on different devices without distortion or unwanted black bars.
Aspect ratio calculation
Aspect ratio = gcd-simplified (width : height)
Decimal ratio = width / height
Missing height = width / decimal ratio
Missing width = height * decimal ratio
Common aspect ratios
| Name | Ratio | Decimal | Use case |
|---|---|---|---|
| Square | 1:1 | 1.00 | Instagram, profile pictures |
| 4:3 | 4:3 | 1.33 | Traditional TV, older monitors |
| 16:10 | 16:10 | 1.60 | Computer monitors |
| 16:9 | 16:9 | 1.78 | HDTV, YouTube, widescreen |
| 21:9 | 21:9 | 2.33 | Ultrawide monitors, cinema |
| 4:5 | 4:5 | 0.80 | Vertical Instagram posts |
| 9:16 | 9:16 | 0.56 | Vertical video, phone screens |
Aspect ratio calculator: frequently asked questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between the width and height of an image, screen, or video. It is expressed as width:height, often in simplified form. For example, 16:9 means the width is 16 units for every 9 units of height. Common aspect ratios include 4:3 (traditional TV), 16:9 (widescreen TV and HD video), 21:9 (ultrawide), and 1:1 (square).
How do I calculate the aspect ratio from dimensions?
Divide the width by the height to get a decimal, then express it as a ratio. For example, an image 1,920 pixels wide and 1,080 pixels high has a ratio of 1,920 / 1,080 = 1.778, which simplifies to 16:9. This calculator simplifies the ratio to its lowest whole numbers automatically.
What are common aspect ratios?
Common aspect ratios include: 4:3 (traditional TV, older monitors), 16:9 (widescreen TV, HD video, modern monitors), 16:10 (some computer monitors), 21:9 (ultrawide monitors and cinema), 1:1 (square images, Instagram posts), 4:5 (vertical Instagram posts), and 9:16 (vertical smartphone video).
How do I find a missing dimension from the aspect ratio?
If you know the aspect ratio and one dimension, multiply that dimension by the ratio. For example, with a 16:9 ratio and a width of 1,920 pixels, the height is 1,920 * (9/16) = 1,080 pixels. Conversely, if you know the height, multiply by the inverse ratio.
Why does aspect ratio matter?
Aspect ratio determines how content appears on different devices. A video created for 16:9 widescreen will have black bars on a 4:3 screen, or may be stretched on a 21:9 ultrawide. Social media platforms have specific recommended aspect ratios for images and videos. Choosing the correct aspect ratio ensures content displays optimally.
Official sources
- Image and video standards: National Institute of Standards and Technology.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.