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About this tool
Calculate simplified ratios and proportional dimensions for thumbnails, banners, and responsive layouts.
The Aspect Ratio Calculator simplifies any width-to-height pair to its lowest terms using the Euclidean GCD algorithm (for example, 1920×1080 simplifies to 16:9), and calculates the matching height or width for a new target size so your image or layout keeps the same proportions.
Open Aspect Ratio Calculator on AltFTool — it loads instantly in your browser.
Type your source size into the Original width and Original height fields, which open on 1920 and 1080. Both are number inputs with a minimum of 1.
Set Target width — it starts at 1280 — to the width you are scaling down or up to. There is no Calculate button; every readout recalculates as you type.
Read Simplified ratio (1920 by 1080 reduces to 16:9), Decimal to four places and Target height in px, check the preview block that mirrors the shape and is captioned '1920 x 1080 preview', then press Reset 16:9 to restore all three fields.
Uses the Euclidean GCD algorithm to reduce any width/height pair to its simplest ratio, not just a rounded approximation.
Enter a target width (or height) and get the exact proportional match, so nothing gets stretched or cropped.
Video resolutions, print sizes, banner ads, thumbnails — any width-and-height pair works the same way.
Type your numbers and get the result immediately.
Enter the width and height, and the calculator divides both by their greatest common divisor (GCD) to reduce them to the simplest ratio — for example, 1920×1080 reduces to 16:9.
16:9. Dividing both numbers by their GCD (120) gives 16:9, the standard widescreen ratio used by most modern video and displays.
Enter your original width and height to get the simplified ratio, then enter your target width — the calculator returns the exact proportional height so the image or layout isn't stretched or distorted.
Yes, completely free with no signup.
Add the Aspect Ratio Calculator widget to your blog or website — free, responsive, no signup. Just keep the “Widget by AltFTool” credit link visible.
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title="Aspect Ratio Calculator — free AltFTool widget"
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