Aspect Ratio Calculator

How It Works

The calculator runs three small jobs on your numbers: reduce them, resize them, and compare them against the sizes people actually ship. Load an image and its pixel dimensions fill in the width and height fields automatically, or just type them.

GCD reduction

The simplest ratio is both dimensions divided by their greatest common divisor, found with the Euclidean algorithm — repeatedly replace the larger number by the remainder until one side reaches zero. For 1920 and 1080 the GCD is 120, so the ratio is (1920÷120):(1080÷120) = 16:9. The divisor is printed alongside the answer so you can verify the arithmetic by hand.

Portrait, landscape, and the decimal check

A width greater than the height is landscape; smaller is portrait; equal is square. The decimal value (width ÷ height) is the fastest cross-check: 1.7778 is 16:9, 1.6 is the 3:2 photo look, 1.0 is square, and anything under 1 flips to vertical. Ratios like 9:16 are the same shape as 16:9 — just rotated — and the tool keeps your orientation as written.

The 4K ladder

Modern displays scale 16:9 by whole steps: 1280×720 → 1920×1080 → 2560×1440 → 3840×2160 → 7680×4320. Each rung is exactly double the previous linear size, meaning four times the pixels — which is why "4K" (3840 wide) needs four Full HD panels to cover it, and why cropping a 4K photo down to 1080p loses no sharpness in the output box.

Frequently Asked Questions