Aspect Ratio Calculator
Calculate and simplify aspect ratios. Resize proportionally with common presets.
Presets
Resized
About Aspect Ratios
An aspect ratio expresses the proportional relationship between width and height. The notation W:H means that for every W units of width, there are H units of height. A 16:9 ratio, for example, means the width is 1.778 times the height. Aspect ratios are simplified using the greatest common divisor (GCD), the same algorithm Euclid described around 300 BCE.
Display aspect ratios standardized around a few key values. Television started at 4:3 (1.333:1), which NTSC and PAL both adopted. Widescreen displays settled on 16:9 (1.778:1) after the ITU recommended it in BT.709. Cinema uses wider ratios: 1.85:1 (Flat) and 2.39:1 (anamorphic Scope). Mobile phones reversed the trend with 9:16 vertical video, now dominant on short-form platforms.
This calculator simplifies any pixel dimensions to their reduced ratio and lets you resize proportionally. Enter a new width to get the correct height (or vice versa). Presets for common display, video, and social media formats are included for quick reference.
Frequently Asked Questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between the width and height of an image or display. It is written as W:H. A 16:9 aspect ratio means the width is 1.778 times the height. Aspect ratios are simplified by dividing both dimensions by their greatest common divisor (GCD).
What is the most common display aspect ratio?
16:9 (1.778:1) is the most common display aspect ratio, used by virtually all modern monitors, TVs, and laptop screens. It was recommended by the ITU in BT.709 and became the standard for HDTV, Full HD (1920x1080), and 4K UHD (3840x2160).
How is an aspect ratio simplified?
An aspect ratio is simplified using the Euclidean algorithm to find the greatest common divisor (GCD) of the width and height, then dividing both by that number. For example, 1920 and 1080 share a GCD of 120, giving 16:9.
What aspect ratio should I use for social media?
It depends on the platform. Instagram posts use 1:1 (square) or 4:5 (portrait). Stories and Reels are 9:16 (vertical). YouTube thumbnails and videos are 16:9 (landscape). Twitter/X images work best at 16:9 or 2:1. LinkedIn posts use 1.91:1 or 1:1.
What is the difference between 16:9 and 16:10?
16:9 (1.778:1) is the standard for video and TV. 16:10 (1.6:1) is slightly taller and historically popular for productivity monitors because the extra vertical space fits more text. Common 16:10 resolutions include 1920x1200 and 2560x1600.