Aspect Ratio Calculator
Enter width and height to get the simplified aspect ratio. Use the scale calculator to resize dimensions proportionally, or pick a common preset like 16:9 or 4:3.
1920 × 1080px
Simplified: 16:9
Scale calculator
Frequently Asked Questions
What is an aspect ratio?
An aspect ratio describes the proportional relationship between width and height. For example, 1920×1080 pixels has an aspect ratio of 16:9, meaning for every 16 units of width there are 9 units of height.
How is the aspect ratio simplified?
The calculator divides both the width and height by their greatest common divisor (GCD) to produce the smallest equivalent whole-number ratio.
How do I scale an image while keeping the ratio?
Enter the original width and height, then type the desired new width in the scale section. The calculator will show the proportional height automatically.
What does the 21:9 ratio look like?
21:9 is an ultrawide cinematic format often used in modern monitors and movies. It is wider than the standard 16:9 widescreen ratio.
Common Aspect Ratios
| Ratio | Decimal | Primary use |
|---|---|---|
| 16:9 | 1.78 | HD video, YouTube, most monitors and laptops |
| 4:3 | 1.33 | Old TV, VGA monitors, iPad (non-Pro) |
| 1:1 | 1.00 | Instagram square posts, avatars |
| 3:2 | 1.50 | DSLR photos, 35 mm film |
| 21:9 | 2.33 | Ultrawide monitors, cinematic video |
| 9:16 | 0.56 | Mobile video (TikTok, Reels, Stories) |
| 2:1 | 2.00 | Panoramic photography, some cinema |
How GCD Simplification Works
The tool divides both dimensions by their Greatest Common Divisor (GCD) using the Euclidean algorithm to produce the smallest whole-number ratio. For example, 1920×1080 simplifies to 16:9 because GCD(1920, 1080) = 120 and 1920/120 = 16, 1080/120 = 9.
Practical Use Cases
- Responsive images — set
aspect-ratio: 16/9in CSS to reserve space before images load and prevent layout shift (CLS). - Video thumbnails — always export at the target ratio to avoid black bars or cropping in YouTube/Vimeo embeds.
- Print design — verify that a designed canvas matches the print paper ratio before sending to press.
- Canvas elements — use the scale calculator to find the exact pixel dimensions of a canvas at any resolution while preserving the ratio.