Skip to content
T
Tools.Town
Free Online Tools for Everyone
Aspect Ratio Calculator illustration

Aspect Ratio Calculator

100% Free

Find the aspect ratio of any size and resize images while keeping the same proportions.

Ratio + Resize
Presets Built-In
Instant Math
100% Client-Side

Original size

Resize to new size

Result

16:9ratio
Decimal
1.7778
Orientation
landscape
Resized dimensions
16:9
1280 × 720px

Keeps the original 16:9 aspect ratio.

Pick a preset or enter any size. Everything is calculated instantly in your browser.

Embed This Tool

Easy to Embed

Add Aspect Ratio Calculator to your website or blog in seconds.

  • Responsive design
  • Lightweight & fast
  • No backend required
  • Always up-to-date 
<iframe
  src="https://tools.town/embed/aspect-ratio-calculator/"
  width="100%"
  height="600"
  style="border:none; border-radius:12px;"
  loading="lazy"
  title="Aspect Ratio Calculator">
</iframe>

Share This Tool

Share Instantly

Share Aspect Ratio Calculator with anyone — no login required.

  • Shareable link
  • No login required
  • Works on any device
  • No account needed

Share via

Advertisement

How to Use

  1. 1 Enter your original width and height, or pick a preset like 16:9 or 1:1
  2. 2 Read the simplified ratio, decimal value, and orientation instantly
  3. 3 Switch to the resize section and choose whether you know the new width or new height
  4. 4 Type the dimension you know — the matching one is solved to keep the ratio
  5. 5 Use the resized dimensions for your export, canvas, or CSS

Features

  • Reduces any width × height to its simplest ratio (e.g. 1920×1080 → 16:9)
  • Shows the decimal ratio and orientation (landscape, portrait, square)
  • Solves the missing dimension when resizing, preserving proportions
  • One-click presets: 16:9, 4:3, 1:1, 21:9, 9:16, 3:2
  • Works for images, video, screens, social posts, and print
  • Runs entirely in your browser — no upload, no sign-up

Why it Matters

Resizing an image or video by eyeballing one dimension is how things end up stretched or squashed. The aspect ratio is the fixed relationship between width and height — get one new dimension and the other is determined. A calculator that reduces the ratio and solves the missing side keeps everything in proportion, which matters for everything from YouTube thumbnails to responsive CSS and print layouts.

★★★★★

Use Cases

Designers & Editors

Resize artwork and exports to new dimensions without distorting them

Video Creators

Check 16:9, 9:16, and 21:9 framing for YouTube, Shorts, and cinema crops

Web Developers

Work out responsive container sizes and CSS aspect-ratio values

Presenters & Print

Match slide and print canvases to a target ratio before you start

What this tool does

The Aspect Ratio Calculator does two jobs. First, it reduces any width × height to its simplest ratio — so 1920×1080 becomes 16:9 — and shows the decimal value and orientation. Second, it resizes: give it one new dimension and it solves the other while keeping the original proportions.

That second part is the one that saves you from stretched, squashed exports.

Common ratios

  • 16:9 — standard widescreen video, YouTube, most monitors and TVs
  • 9:16 — vertical video, Reels, TikTok, Shorts, Stories
  • 1:1 — square, profile pictures and some social posts
  • 4:3 — classic displays, many cameras and slides
  • 21:9 — ultrawide and cinematic crops
  • 3:2 — common DSLR and print ratio

How the math works

The simplified ratio comes from the greatest common divisor (GCD) of the two dimensions. For 1920 and 1080 the GCD is 120, so 1920/120 : 1080/120 = 16:9. Resizing uses simple cross-multiplication: new height = new width × original height ÷ original width.

Privacy

The calculation runs entirely in your browser via the pure calculateAspectRatio function. Nothing is uploaded — you can verify this in your browser’s Network tab.

Frequently Asked Questions

What does an aspect ratio like 16:9 mean?
It's the proportional relationship between width and height. 16:9 means for every 16 units of width there are 9 units of height. It doesn't fix the size — 1280×720, 1920×1080, and 3840×2160 are all 16:9. The calculator finds this ratio by dividing both dimensions by their greatest common divisor.
How do I resize an image without distorting it?
Keep the aspect ratio constant. Decide on one new dimension — say a width of 1280px — and let the height follow the original proportions. For a 1920×1080 image, the matching height is 720px. This tool does that automatically: pick which dimension you know and it solves the other.
What's the difference between landscape, portrait, and square?
Landscape means the width is greater than the height (e.g. 16:9). Portrait means the height is greater (e.g. 9:16, common for phone video and Reels). Square is a 1:1 ratio, popular for profile pictures and some social posts. The calculator labels the orientation for you.
Can I use this for the CSS aspect-ratio property?
Yes. The simplified ratio it gives — for example 16 / 9 — is exactly what you put into the CSS aspect-ratio property. You can also use the decimal value if you prefer. This keeps responsive elements proportional without fixed pixel heights.
Does it work for non-standard sizes?
Yes. Any width and height work, and the tool reduces them to the simplest whole-number ratio it can. If the numbers don't share a common factor (a coprime pair), the ratio is shown as-is, which is still correct.
Is anything uploaded?
No. The calculation runs entirely in your browser via the pure `calculateAspectRatio` function. There are no network calls — you can confirm this in your browser's Network tab.
📖

Want to understand the math?

Browse all guides →
Aspect Ratios Explained
aspect ratio

Aspect Ratios Explained: 16:9, 4:3, and How Resizing Works

A practical guide to aspect ratios — what 16:9 and 9:16 mean, how to resize images without distortion, and how to use the CSS aspect-ratio property.

23 Jun 2026

5 min read

Related Tools You Might Like

Color Palette Generator

Generate harmonious palettes from any base color — complementary, analogous, triadic, tetradic, split-complementary, monochromatic.

Image Resizer

Resize images to any dimension while preserving aspect ratio. Free and instant.

Image Cropper

Crop images to any size or aspect ratio with a drag-and-drop interface.

Border Radius Generator

Visually craft CSS border-radius with per-corner sliders, live preview, unit toggle (px/em/rem/%), and shorthand collapsing.

Box Shadow Generator

Visually craft CSS box-shadow — offset, blur, spread, color, opacity, inset toggle, plus Material-style elevation presets.

Browse more free tools
More Design Tools All categories