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Aspect Ratio Calculator

Simplifies any dimensions to a ratio, solves for a missing side, and shows how much crop each social platform costs you.

Lab Nothing uploaded No sign-up Free, unlimited
Lab tool
Enter your figures and press Calculate ratio.
In short An aspect ratio is width divided by height reduced to its smallest whole numbers, so 1920×1080 is 16:9 and 1080×1350 is 4:5. Two things about it surprise people. Odd-looking ratios like 683:384 are usually correct rather than broken — they appear when the pixel dimensions have no small common factor, which happens constantly with cropped screenshots and scaled exports. If you want a clean ratio you have to choose dimensions that produce one. The more useful part is the crop table. Every platform has its own frame, and posting one image everywhere means something gets cut: a 16:9 landscape video loses roughly half its width when forced into a 9:16 story, and a square crop of a 4:5 portrait loses the top and bottom. Knowing which platform costs you what is the difference between composing once and reshooting. The practical technique is to shoot in the widest ratio you need and compose with safe margins — keep the subject inside the area that survives the tightest crop, and let the edges be sacrificial. That way one capture serves every destination, and the calculator tells you exactly how much margin each destination demands.

How to use the Aspect Ratio Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the Aspect Ratio Calculator

The Aspect Ratio Calculator simplifies any dimensions to a ratio, solves for a missing side, and shows how much crop each social platform costs you. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Resizing an image without distorting it.
  • Working out how much of a 16:9 frame survives a crop to 9:16.
  • Checking a video export against platform requirements.

The maths behind it

This tool uses ratio = width ÷ height, simplified by the greatest common divisor. Solving for a side: new height = new width ÷ ratio. Every intermediate value is shown on screen, so the result can be checked by hand.

Explained in our guides

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Frequently asked questions

Why does my ratio show as something odd like 683:384?
Because the dimensions are not an exact multiple of a standard ratio, usually after a manual crop. The nearest standard ratio is shown alongside so you can see what it is close to.
How do I shoot once and post everywhere?
Frame for the tightest crop from the start. Going 16:9 to 9:16 removes about two-thirds of the width, so anything essential has to sit inside the middle third of the original frame.
Does the Aspect Ratio Calculator cost anything?
No charge and no sign-up. There is no free tier to run out of because there is no paid tier — inputtesthub.com is funded by advertising rather than by metering the utility.
Does anything I enter leave my computer?
No. The Aspect Ratio Calculator runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
Can I check the maths myself?
It uses ratio = width ÷ height, simplified by the greatest common divisor. Solving for a side: new height = new width ÷ ratio. The full working is printed under the result, so you can follow every step rather than trusting a black box.
Who is the Aspect Ratio Calculator for?
In practice it gets used for three things: resizing an image without distorting it. Working out how much of a 16:9 frame survives a crop to 9:16. Checking a video export against platform requirements. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Is the number rounded?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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