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Aspect Ratio Calculator

Lock an aspect ratio, type any width or height, and get the matching dimension instantly — no stretched, squashed, or letterboxed video.

Free · No sign-up · Runs in your browser
Target aspect ratio
Custom ratio
:
16:9
Simplified ratio
16:9
Decimal
1.778
Dimensions
1920×1080

Keep recording and editing together. ScreenBuddy adds zoom, captions, and local MP4 or GIF export on Mac and Windows.

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How it works

01

Pick a ratio

Choose a preset like 16:9 or 9:16, or type your own custom ratio.

02

Enter one dimension

Type a width or a height — the other value updates automatically to stay in ratio.

03

Use the result

Read the simplified ratio and exact pixel dimensions for your export or canvas.

What is an aspect ratio calculator?

An aspect ratio calculator keeps width and height in proportion so a video or image does not stretch. Lock 16:9, 9:16, 1:1, 4:3, 21:9, or a custom pair, type one dimension, and the other follows. Use it when you are sizing a canvas, an export, or a social crop and need exact pixels rather than a guess.

Aspect ratios, explained

An aspect ratio describes the relationship between a frame’s width and its height, written as width:height. It does not fix the resolution — 1280×720 and 1920×1080 are different sizes but the same 16:9 shape. Getting the ratio right is what keeps your video filling the screen on its target platform without black bars or stretching.

The ratios you will actually use

  • 16:9 — the standard for YouTube, desktop screens, and most screen recordings.
  • 9:16 — vertical video for TikTok, Instagram Reels, and YouTube Shorts.
  • 1:1 — square, popular for in-feed social posts.
  • 4:3 — older displays, some slides and tablets.
  • 21:9 — ultrawide and cinematic framing.

Resize without distortion

The golden rule of resizing is to scale width and height by the same factor. If you halve the width, halve the height. This calculator enforces that for you: lock a ratio, change one dimension, and the other follows so the proportions never break.

Converting between ratios

Moving footage between ratios — say 16:9 to 9:16 for a vertical cut — is not a pure resize; it is a re-frame. You either crop (lose part of the image) or pad (add bars). Decide which subject must stay in frame, then use the calculator to nail the exact target dimensions.

How do I convert a 16:9 screen recording to 9:16?

Select 9:16, enter the target width (1080 is the usual Shorts/Reels/TikTok width), and read 1920 for height. That is a re-frame, not a lossless resize: the sides of a desktop recording will crop. Place the important control near the center before you export, then preview on a phone. ScreenBuddy can output common shapes from the same project; still verify captions and zoom after the crop.

ScreenBuddy for Mac and Windows includes common horizontal, square, and vertical output options, so one walkthrough can be framed for different channels. See how it works.

Related: FPS to milliseconds converter · video bitrate calculator · screen resolution / PPI calculator.

FAQ

Frequently Asked Questions

What is the 16:9 aspect ratio in pixels?
The 16:9 ratio scales to many resolutions: 1920×1080 (1080p), 2560×1440 (1440p), 3840×2160 (4K), and 1280×720 (720p) are all exactly 16:9. Type any width into the calculator with 16:9 selected and it returns the matching height.
How do I convert a video to vertical 9:16?
Select the 9:16 preset, then enter your target width (1080 is standard for Reels, Shorts, and TikTok) to get a height of 1920. Keep in mind that re-framing 16:9 footage to 9:16 crops the sides — you choose what stays in frame.
What does the simplified ratio mean?
It is your current width and height reduced to their smallest whole-number ratio using the greatest common divisor. For example 1920×1080 simplifies to 16:9, and 1080×1080 simplifies to 1:1. It is a quick way to confirm two dimensions share the same shape.
Why does keeping aspect ratio matter?
If you resize width and height independently, the image stretches or squashes. Scaling both by the same ratio keeps circles round and faces natural. This calculator always keeps the locked ratio so your output never distorts.
What size is 1920×1080 in 16:9?
1920×1080 is exactly 16:9, the same shape as 1280×720 and 3840×2160. Type 1920 with 16:9 locked and the height is 1080. Type 1080 with 9:16 locked and the height is 1920 for a vertical cut.
Can ScreenBuddy export more than 16:9?
Yes. ScreenBuddy includes common horizontal, square, and vertical output options so one walkthrough can be framed for a landing page, a feed, or documentation. Recheck zoom targets after you change the canvas.
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<iframe src="https://screenbuddy.xyz/embed/aspect-ratio-calculator" title="Aspect Ratio Calculator" width="100%" height="640"
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<p style="font:14px/1.5 system-ui,sans-serif;margin:8px 0 0">
  <a href="https://screenbuddy.xyz/tools/aspect-ratio-calculator">Aspect Ratio Calculator</a> by <a href="https://screenbuddy.xyz">ScreenBuddy</a>
</p>

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Frame one recording for different destinations

Choose a horizontal, square, or vertical canvas in ScreenBuddy. Recheck zoom targets, captions, and webcam placement for each shape before exporting the demo.

Mac & Windows. No card. Record, edit, and preview free. A one-time license is required to save or export. Media processing stays on your device. Internet is required for license activation and update checks.

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