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Aspect Ratio Calculator

Calculate image and video aspect ratios. Enter any two values to find the third, or pick a preset ratio for common video and social media sizes.

Common presets

Aspect Ratio

16:9

Decimal

1.7778

Percentage (W/H)

177.78%

Visual preview

16:91,920px1,080px

CSS

aspect-ratio: 16 / 9;

How to Use Aspect Ratio Calculator

  1. 1Enter the width and height of your image or video.
  2. 2The aspect ratio and simplified fraction are shown instantly.
  3. 3Or pick a preset ratio and enter one dimension to calculate the other.
  4. 4View common resolutions for the selected ratio.
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Frequently Asked Questions

What is an aspect ratio?▾
An aspect ratio describes the proportional relationship between an image or video's width and height, expressed as W:H. For every W units of width there are H units of height. For example, 16:9 means for every 16 pixels of width there are 9 pixels of height. This ratio stays the same regardless of the actual pixel dimensions, so 1920×1080 and 1280×720 both share the 16:9 ratio.
What are the most common aspect ratios and where are they used?▾
16:9 is the universal widescreen standard for HD video, YouTube, TV, and most modern monitors. 4:3 was the original TV and monitor standard and is still common for presentations and older iPad models in landscape. 21:9 (ultrawide cinema) is used for cinematic films and ultrawide monitors. 1:1 (square) is used for Instagram posts and profile pictures. 3:2 matches the 35mm film frame and is used by most DSLR/mirrorless cameras. 9:16 (portrait) is the vertical video format for TikTok, Instagram Reels, and Stories. 2:3 is the portrait orientation of the 3:2 DSLR ratio.
How do pixel dimensions relate to aspect ratio?▾
Pixel dimensions are a specific instance of an aspect ratio. To find the aspect ratio from dimensions, divide both numbers by their greatest common divisor (GCD). For example, 1920÷160=12 and 1080÷160=6.75 — instead use GCD(1920,1080)=120, giving 16:9. Common 16:9 resolutions: 1280×720 (720p), 1920×1080 (1080p FHD), 2560×1440 (2K QHD), 3840×2160 (4K UHD). For 4:3: 1024×768, 1280×960. For 1:1: 1080×1080 (Instagram).
How do I maintain aspect ratio in CSS and responsive design?▾
Modern CSS: use aspect-ratio: 16 / 9 directly on the element — the height auto-adjusts to match the width. For responsive video embeds, wrap the iframe/video in a container with aspect-ratio: 16/9, width: 100%, and set the child to width: 100%; height: 100%. The legacy padding-bottom hack (height: 0; padding-bottom: 56.25% for 16:9) still works in older browsers. For images, set width: 100%; height: auto to preserve the natural ratio.
How do I calculate a new width or height while keeping the same aspect ratio?▾
If you know the target width and the ratio (W_r:H_r): new height = width × (H_r / W_r). For example, 1280px wide at 16:9 → height = 1280 × (9/16) = 720px. If you know the target height: new width = height × (W_r / H_r). Use the "Lock Ratio" toggle in this calculator to do this automatically — enter one dimension and the other updates instantly to preserve the ratio.