Aspect Ratio Calculator
Show the math
What Your Result Means
- Aspect Ratio: The simplified width-to-height proportion of your image or screen, reduced using the greatest common divisor. Common ratios include 16:9 (widescreen), 4:3 (classic TV), and 1:1 (square).
- Calculated Height: The proportional height for a new width that preserves the original aspect ratio.
- Calculated Width: The proportional width for a new height that preserves the original aspect ratio.
How This Calculator Works
You enter a width and height in pixels. The tool computes their greatest common divisor (GCD) using the Euclidean algorithm and divides both dimensions by it to produce the simplest whole-number ratio. The resize section applies the original width-to-height proportion to compute a matching dimension.
Quick Questions
Why does 1920×1080 simplify to 16:9?
The GCD of 1920 and 1080 is 120. Dividing both by 120 gives 16 and 9, so the aspect ratio is 16:9. This is the standard widescreen format used by most monitors and TVs.
What ratio should I use for social media?
Instagram feed posts typically use 1:1 (square) or 4:5 (portrait). Stories and Reels use 9:16 (vertical). YouTube thumbnails and videos use 16:9. Twitter/X images perform well at 16:9 or 2:1.
Can I enter non-pixel values like inches or centimeters?
Yes, the ratio is purely mathematical — it works with any unit as long as both dimensions use the same unit. The "px" label is just a default hint for digital use.
Why does my ratio show unusual numbers like 683:384?
Non-standard dimensions may not reduce to a familiar ratio. This happens with cropped or resized images. The result is still mathematically correct; it just does not match a common preset.
Sources
- Wikipedia — Aspect Ratio (image) (standard ratios and history)
- Wikipedia — Euclidean Algorithm (GCD computation method)
Method & review
Estimate only. Results reflect your inputs and standard formulas. Double-check important decisions independently.