Practical Tools
Image

Aspect Ratio Calculator

Find the aspect ratio of any width and height, or calculate a missing dimension from a known ratio. Works for images, videos, screens, and print layouts. Free, no signup.

What do you want to find?
Enter values above to calculate.

How to use this tool

  1. 1Choose what you want to find: 'Find ratio' to calculate the ratio from a width and height, 'Find height' to calculate height from a width and ratio, or 'Find width' to calculate width from a height and ratio.
  2. 2Enter the known values in the input fields.
  3. 3The result updates instantly. 'Find ratio' shows the simplified ratio (e.g. 16:9). 'Find height' and 'Find width' show the calculated pixel dimension.

Formula used

Aspect ratio: divide both dimensions by their greatest common divisor (GCD) to get the simplified ratio. To find the height: height = width / (ratio width / ratio height). To find the width: width = height x (ratio width / ratio height).

Example

Find the ratio of a 1920x1080 image

Choose 'Find ratio', enter width 1920 and height 1080. Result: 16:9. This is the standard widescreen ratio for HD monitors, TVs, and video.

Find the height for a 1200px wide 16:9 banner

Choose 'Find height', enter width 1200, ratio width 16, ratio height 9. Result: 675 px. The banner should be 1200 x 675 px to maintain 16:9.

Common use cases

  • Working out the correct height for a banner at 1200px wide that must be 16:9
  • Checking whether an uploaded image matches a required 4:3, 16:9, or 1:1 ratio
  • Scaling a 1920x1080 video to 1280px wide while keeping the correct height
  • Generating consistent thumbnail sizes from a design brief that specifies a ratio
  • Calculating crop dimensions for a product image grid that requires a uniform ratio

Common mistakes

  • Entering width and height in the wrong order - width is always the horizontal dimension (wider), height is the vertical dimension (taller).
  • Expecting this calculator to resize the actual image - this is a maths tool only. Use the Image Resizer to change an image's actual pixel dimensions.
  • Confusing display ratio with pixel ratio - a 4K monitor (3840x2160) and an HD monitor (1920x1080) both have a 16:9 ratio, but different pixel counts.

Frequently asked questions

What is the aspect ratio of 1920x1080?

1920x1080 is a 16:9 aspect ratio. This is the standard widescreen format for HD monitors, televisions, most laptop screens, and video formats like YouTube.

What are common standard aspect ratios?

16:9 is standard widescreen (TV, YouTube, most monitors). 4:3 is older square-ish format (older TVs, some tablets). 1:1 is square (Instagram posts). 9:16 is vertical (Instagram Stories, TikTok, phone screens). 3:2 is common in photography.

What is 4:3 in pixels?

Common 4:3 sizes include 800x600, 1024x768, and 1400x1050. Use 'Find width' or 'Find height' mode with ratio 4:3 to calculate any 4:3 size from a single known dimension.

Does this calculator resize the actual image?

No. This is a calculation tool only - it tells you what dimensions to use. Use the Image Resizer to actually resize an image to the calculated dimensions.

What is a greatest common divisor (GCD)?

The GCD is the largest number that divides both dimensions evenly. Dividing both width and height by the GCD gives the simplest form of the ratio. For 1920x1080, the GCD is 120, giving 16:9.

What aspect ratio should I use for social media?

Instagram feed: 1:1 (square) or 4:5 (portrait). Instagram Stories: 9:16. YouTube: 16:9. LinkedIn: 1.91:1 (banner) or 1:1 (post). Twitter/X: 16:9 for in-feed images. Each platform has recommended pixel sizes - use 'Find height' or 'Find width' to calculate the missing dimension.

Related tools

Last updated