Aspect Ratio Calculator

Divide the width and height by their greatest common divisor. For 1920 × 1080 the greatest common divisor is 120, so the ratio is 16:9. To resize while keeping the ratio, multiply the new width by the original height divided by the original width: 1280 × 1080 ÷ 1920 = 720.

Common 16:9 resolutions include 1280 × 720 (HD), 1920 × 1080 (Full HD), 2560 × 1440 (QHD) and 3840 × 2160 (4K UHD). 16:9 is the standard for online video, televisions and most computer and phone screens used in landscape.

Because it is not exactly 16:9. 1366 ÷ 768 is about 1.7786, while 16:9 is 1.7778, a difference of roughly 0.05%. The resolution is marketed as 16:9 because it is close enough to look identical. This calculator shows the true simplified ratio and tells you which standard ratio it is nearest to.

Usually not. Ultrawide monitors sold as 21:9, such as 2560 × 1080, are mathematically 64:27, about 2.37:1, while true 21:9 is 2.33:1. The name is a rounded marketing label. When a layout or video must match a specific screen exactly, calculate from the actual pixel dimensions.

Vertical video for phones is 9:16, typically 1080 × 1920 pixels — the format used by stories and short-form video feeds. Portrait photos and feed posts often use 4:5, and square 1:1 remains the safest choice when one image has to fit many placements. Check each platform's current guidance, as recommended sizes change.

Use the aspect-ratio property, for example aspect-ratio: 16 / 9, on an element with a set width. The browser calculates the height automatically, which prevents layout shift while images, videos and embeds load. This calculator gives you the simplified value ready to copy.