Aspect Ratio Calculator
Simplify any width and height to its aspect ratio, and scale it to a new width without distortion.
How it works
ratio = (w ÷ gcd) : (h ÷ gcd) · new height = new width × h ÷ w
An aspect ratio is the width-to-height fraction in lowest terms, found by dividing both sides by their greatest common divisor. Keeping the ratio constant is what preserves shape when you resize: multiply or divide both dimensions by the same factor. The scaled height can come out fractional — for pixel work, round to the nearest whole (or even) pixel.
Worked example
1920×1080: the GCD is 120, so the ratio is 16:9 (1.778:1). Scaling to 1280 wide keeps the ratio: 1280 × 1080 ÷ 1920 = 720, giving 1280×720.
Frequently asked questions
Why does 1366×768 give the weird ratio 683:384?
Because that is mathematically exact — the GCD is only 2. It works out to 1.779:1, visually identical to 16:9 (1.778:1); the panel was a cost-driven near miss, which is why everyone still calls it 16:9.
What are the common ratios?
16:9 for video and monitors, 4:3 for older screens and some tablets, 3:2 for many laptops and photos, 1:1 for square images, 21:9 for ultrawides, and 9:16 for vertical phone video.
How do I fit a 16:9 video into a 1:1 frame?
You can’t without a compromise: crop the sides, letterbox with bars, or stretch (never stretch). Cropping loses a third of the width — plan the shot for the destination ratio when you can.
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This calculator is for educational purposes. Double-check important results before acting on them.