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Free Aspect Ratio Calculator — Simplify & Reverse

A free aspect ratio calculator takes a width and height, simplifies them to lowest terms with the GCD algorithm (for example 1920×1080 → 16:9), and lists common matching resolutions. In reverse mode, pick a standard ratio like 16:9, 1:1, 4:3, or 21:9, enter one dimension, and get the other automatically — no signup, pure browser math.

Designers, editors, and developers enter pixel width and height to get the exact simplified aspect ratio, a decimal form, orientation, and a live preview frame. Matching presets (Full HD, 4K, Instagram, ultrawide, and more) appear when they share the same simplified ratio. Switch to From standard ratio, choose 16:9, 1:1, 4:3, 21:9, or other common ratios, enter width or height, and the missing side is calculated instantly. Uses Euclidean GCD in plain JavaScript — free, no signup, no backend.

Mode
Aspect ratio
16:9
Decimal
1.777778
Orientation
Landscape

Common matching resolutions

  • HD Ready1,280×720
  • HD+1,600×900
  • Full HD1,920×1,080
  • QHD2,560×1,440
  • 4K UHD3,840×2,160
  • 5K5,120×2,880
  • 8K UHD7,680×4,320
  • YouTube thumbnail1,280×720

Runs 100% in your browser. Your data never leaves your device.

Simplifies ratios with the Euclidean GCD algorithm in plain JavaScript, including a decimal-scale step so non-integer sizes still reduce correctly. Reverse mode multiplies or divides by the chosen ratio pair. Matching resolutions compare simplified W:H against a curated list of common display and social sizes — no libraries or server calls.

How to Use Aspect Ratio Calculator

  1. Choose Find ratio or From standard ratio at the top
  2. Find ratio: enter width and height in pixels to see the simplified ratio, decimal, and matching resolutions
  3. From standard ratio: pick a preset (16:9, 1:1, 4:3, 21:9, …), choose whether you know width or height, and enter that value
  4. Read the calculated other dimension and optional resolution matches below

When Would You Use This?

Video editors checking whether a timeline is truly 16:9 paste the export size and confirm the simplified ratio before uploading to YouTube.

Designers sizing a hero image for a 21:9 ultrawide mockup enter the known width and get the exact height without spreadsheet math.

Social managers converting a landscape shot to a square or story format look up matching Instagram resolutions that share the same aspect ratio.

Frequently Asked Questions

Is this aspect ratio calculator free to use?
Yes, completely free. No signup, no login, no payment ever.
Do I need to create an account?
No account needed. Enter dimensions or pick a standard ratio and see results immediately.
Is my data safe?
Everything runs in your browser. Width and height values are never uploaded to our servers.
How is the ratio simplified?
We divide width and height by their greatest common divisor (GCD) using the Euclidean algorithm, so 1920×1080 becomes 16:9 and 800×600 becomes 4:3.
What does reverse mode do?
You pick a standard ratio and enter either width or height. The tool calculates the other dimension so the pair matches that ratio exactly.
Why are some common resolutions missing from the list?
Only presets that simplify to the exact same W:H as your input are listed. A near-widescreen size that reduces to a different ratio will not appear.
Does this work offline?
Yes. Once the page has loaded, all calculations work fully offline.

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