Aspect Ratio Calculator
Find the aspect ratio of any screen, photo or video, or resize to new dimensions without stretching.
How it works
Find ratio: enter a width and height. We divide both by their greatest common divisor to get the simplest whole-number ratio, like 1920 × 1080 → 16:9.
If the result isn't a familiar ratio, we show the closest common one, handy for photos like 1000 × 667, which is almost exactly 3:2.
Resize: enter a ratio (or original size) and one new dimension. The other is calculated so the shape stays the same. The preview updates as you type.
Formula
ratio
Where:
- W, H
- = Original width and height
- gcd
- = Greatest common divisor of W and H
Worked example
A 1920 × 1080 video needs to be 1280 pixels wide.
gcd(1920, 1080) = 120, so the ratio is 16:9. New height = 1280 × 9 ÷ 16 = 720 pixels.
Strategic Design and Social Media Planning
When designing for modern digital platforms, prioritizing 'safe zones' within standard ratios is crucial for professional results. For vertical video platforms like TikTok or Instagram Reels, the 9:16 ratio is the standard, but essential elements like text and logos should be kept within the center 80% to avoid being covered by UI overlays or cropped on different screen sizes. Using a calculator to pre-determine these pixel boundaries helps maintain visual integrity across a wide variety of mobile devices.
Avoiding Distortions and Common Errors
A frequent mistake in digital imaging is resizing a canvas by entering arbitrary pixel values without locking the proportions. This leads to 'anamorphic stretching,' where subjects appear unnaturally wide or thin, making the final output look amateurish. Another subtle error is confusing the 16:9 widescreen standard with the 16:10 ratio commonly found on productivity laptops. While they look similar at a glance, a 16:9 video played on a 16:10 screen will result in letterboxing.
Real-World Applications in Development
Web developers use aspect ratio calculations to implement the CSS 'aspect-ratio' property, which reserves space for images before they load. This prevents the frustrating 'layout shift' that occurs when content jumps around, improving the site's user experience. Professional photographers also utilize these tools to prepare 3:2 sensor images for 4:5 print frames, ensuring that no critical parts of their artistic composition are accidentally cropped out by automated printing software.
Frequently asked questions
16:9 for HD video, TVs and most monitors; 4:3 for older screens and many tablets; 3:2 for DSLR photos; 1:1 for square posts; and 9:16 for vertical video like Stories, Reels and TikTok.