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Video Aspect Ratio & Resolution Calculator

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Lock the aspect ratio you want and compute the matching width or height — instantly. Perfect for cropping, exporting, and resizing video for YouTube, Shorts, Reels, TikTok, and ultrawide screens.

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About Video Aspect Ratio & Resolution Calculator

Every video export has two numbers that must be exactly right: width and height in pixels. Get either one wrong and the encoder either rejects the file (H.264 and H.265 require even pixel dimensions for chroma subsampling) or the platform displays it cropped, letterboxed, or squashed. The calculation is straightforward, but it is easy to round in the wrong direction or to forget which number to lock when resizing.

The AT USE Video Aspect Ratio Calculator removes the arithmetic. Enter any two of the three values — width, height, or aspect ratio — and the third fills in automatically. Results are snapped to the nearest even integer, so you never get a 1079-pixel height that breaks an H.264 encode. Use the preset chips to jump to the most common delivery targets: 16:9 for YouTube and standard widescreen, 9:16 for YouTube Shorts, Instagram Reels, and TikTok, 1:1 for Instagram square, 4:5 for Instagram portrait, 2:3 for Pinterest, and 21:9 for ultrawide cinematic exports.

Video editors use it when exporting a sequence at a non-standard size — entering the source width and the target ratio to get the correct height without mental math. Social media managers use it to plan a crop before going into an editor — checking whether a 16:9 clip can be reformatted to 9:16 without losing the subject. Developers use it when sizing a <video> element or a canvas to an exact aspect ratio. All calculations run in the browser; no data is sent anywhere.

Common use cases

  • Planning a 9:16 crop from a 16:9 source: A video editor has a 1920x1080 clip and wants to post a 9:16 version to Reels without re-shooting. Entering height 1080 with ratio 9:16 shows that the Reels frame would be 608x1080 — only 608 pixels wide of the original 1920. That is a significant center crop; the editor can decide whether the subject fits within that 608-pixel column or whether a 1:1 crop is a better choice for this particular clip.
  • YouTube 4K export dimensions: A creator rendering a 4K export types 3840 in the Width field with ratio 16:9 and reads 2160 in the Height field — the correct UHD dimensions for a YouTube 4K upload. No calculator app needed, no mental math.
  • HTML &lt;video&gt; responsive sizing: A developer needs to set an explicit width and height attribute on a video element for a 4:5 crop at 400px wide (required for correct aspect-ratio hint in browsers without the aspect-ratio CSS property). Entering width 400 with ratio 4:5 returns height 500 — the correct value to add to the HTML attribute.
  • Checking whether a clip meets a platform minimum: A social media manager plans a 720p 1:1 crop for Instagram. Entering 720x720 and comparing to Instagram's 500x500 minimum confirms the clip meets the requirement. Entering the ratio and a width of 499 immediately shows 499x499 — below the minimum — which is useful when checking whether a low-resolution source clip can be posted without upscaling.
  • Ultrawide cinema export planning: A filmmaker exporting a 21:9 cut at a target width of 2560px enters 2560 with ratio 21:9 and reads height 1097 (snapped from 1097.1). This is the correct height to enter in DaVinci Resolve or Premiere's custom export settings for a 2560px-wide ultrawide master.

How to use it

  1. Click a preset chip (16:9, 9:16, 1:1, 4:5, 21:9) or type a custom ratio.
  2. Enter either the target width or the target height.
  3. Read the computed value, snapped to a codec-safe even number.
  4. Use it to plan exports, crops, or resizes across platforms.

Frequently asked questions

Why does my encoding software reject the dimensions this calculator gives me?

Most codecs require even dimensions and the calculator snaps to even integers. If your encoder still rejects the result, check whether your encoder requires dimensions that are divisible by 4 or by a larger macro-block size (some older hardware encoders require multiples of 16). In that case, round the computed value up to the next multiple of 4 or 16 manually.

What is 4:5 and why is it used on Instagram?

4:5 is the tallest portrait ratio Instagram allows without cropping in the feed (1080x1350 pixels). Taller ratios are cropped to 4:5 in the grid view. Portrait posts get more vertical screen space on a phone than square posts, which is why 4:5 rather than 1:1 is the preferred ratio for still and video posts aimed at maximizing visual impact on mobile.

The 16:9 preset gives me a height of 1080 at 1920 width. What about 720p and 1080p 16:9 resolutions?

Standard 16:9 resolutions: 3840x2160 (4K UHD), 2560x1440 (1440p / 2K), 1920x1080 (1080p Full HD), 1280x720 (720p HD), 854x480 (480p SD). Enter any of these widths with the 16:9 preset to confirm the exact corresponding height. All divide evenly so no snapping occurs.

Can I use this for image aspect ratios, not just video?

Yes. The calculator is a pure ratio-and-dimension tool. It works identically for print layouts, web images, CSS containers, and canvas elements. The "snap to even number" behavior is only relevant for video encoders; for image and CSS use cases, even-number snapping is harmless because image formats do not have the chroma subsampling constraint.

What if I want to type the ratio as a decimal like 1.778?

The Ratio field accepts decimals. Type 1.778 (or 1.7778 for higher precision) and the width/height calculation runs from that decimal. The preset chips populate the field as a decimal internally — 16:9 stores as 1.7778. Typing a decimal is useful when your source encoder or spec sheet gives the ratio as a decimal rather than a fraction.

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