Aspect Ratio Calculator
Calculate and convert image and video aspect ratios
Aspect Ratio
16:9
Decimal Ratio
1.7778
Orientation
Landscape
Scale to New Dimensions
About Aspect Ratio Calculator
Aspect Ratio Calculator is a free online tool that calculates, converts, and maintains aspect ratios for images, videos, and screen designs. Enter dimensions to find the ratio, or enter a ratio and one dimension to calculate the other — ensuring images and videos scale proportionally without distortion.
An aspect ratio is the proportional relationship between the width and height of a rectangular element, expressed as W:H. A 16:9 video is 16 units wide for every 9 units tall — 1920×1080, 1280×720, and 3840×2160 are all 16:9 because they share the same reduced ratio. Maintaining the aspect ratio when resizing prevents the squishing or stretching that makes images and videos look amateurish.
Common aspect ratios serve different contexts. 16:9 is the universal standard for HD and 4K video, YouTube, and widescreen monitors. 4:3 is the legacy TV and monitor standard, still used in some video call layouts. 1:1 is the square format popularised by Instagram (and still dominant in Instagram feed posts). 9:16 is the vertical smartphone format used by Instagram Reels, TikTok, and YouTube Shorts. 3:2 is the classic 35mm photography format used by most DSLR cameras. 4:5 is Instagram's optimal portrait format.
For web designers and developers, aspect ratio calculations come up constantly: setting CSS aspect-ratio for responsive embedded videos, calculating image dimensions for a design grid, finding the correct thumbnail crop for a video, or determining banner ad dimensions. The CSS aspect-ratio property (aspect-ratio: 16/9) is now supported in all modern browsers and eliminates the need for the old padding-bottom hack for responsive video embeds.
How to Use Aspect Ratio Calculator
- 1Enter the width and height to calculate the aspect ratio
- 2Or enter a known ratio (e.g. 16:9) and one dimension to find the other
- 3Use the lock-ratio mode to calculate new dimensions after resizing
- 4Copy the calculated dimensions into your design or video tool
Frequently Asked Questions
16:9 is the universal standard for HD and 4K video, used by YouTube, Vimeo, Netflix, and all modern TV broadcasting. It replaced the older 4:3 standard in the mid-2000s with the transition to widescreen displays.
Square posts: 1:1 (e.g. 1080×1080 px). Portrait posts: 4:5 (e.g. 1080×1350 px) — Instagram's preferred portrait ratio that takes up the most feed space. Landscape: 1.91:1 (e.g. 1080×566 px). Stories and Reels: 9:16 (e.g. 1080×1920 px).
Keep the ratio of width to height constant. If you scale the width by a factor, scale the height by the same factor. For example, to resize a 1920×1080 image to 1280 wide: 1280 ÷ 1920 = 0.667; new height = 1080 × 0.667 = 720 px. The result (1280×720) maintains the 16:9 ratio.
Aspect ratio is the proportional relationship (16:9, 4:3, 1:1). Resolution is the actual pixel dimensions (1920×1080). Multiple resolutions can share the same aspect ratio — 3840×2160 (4K) and 1280×720 (720p) are both 16:9.
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