Find the aspect ratio of any image or screen, or calculate a new width or height that keeps the same shape.
An aspect ratio is the shape of a picture or screen, written as width to height. Keeping it the same is what stops images and videos from looking stretched or squashed when you resize them. This calculator finds the ratio of any size and works out the missing width or height for a new size, using presets for the most common formats.
How do I calculate an aspect ratio?
Divide the width and height by their greatest common divisor. For 1920 × 1080, the common divisor is 120, giving 16:9. To resize while keeping that shape, use new height = new width × original height ÷ original width.
Common aspect ratios
| Ratio | Used for | Example sizes |
|---|---|---|
| 16:9 | YouTube, TVs, laptop screens | 1280×720, 1920×1080, 3840×2160 |
| 9:16 | Reels, TikTok, Shorts, Stories | 1080×1920 |
| 4:3 | Older TVs, iPads, many phone photos | 1024×768, 1600×1200 |
| 1:1 | Profile pictures, square posts | 1080×1080 |
| 4:5 | Instagram portrait posts | 1080×1350 |
| 21:9 | Ultrawide monitors, cinema | 2560×1080, 3440×1440 |
The resize formula
New width = new height × (original width ÷ original height)
How to use the Aspect Ratio Calculator
Enter the original size
Type the width and height in pixels, or tap a preset such as 16:9.
Enter a new width or height
Type one new dimension and the other is calculated to keep the same shape.
Read the ratio and new size
The simplified ratio appears in large text, with the decimal ratio and the new size underneath.
Frequently asked questions
What aspect ratio is 1920 × 1080?
1920 × 1080 is 16:9.
What is the aspect ratio for Instagram Reels?
Reels, TikTok and YouTube Shorts use 9:16, usually 1080 × 1920 pixels.
How do I resize without stretching?
Keep the aspect ratio the same. Enter your new width here and use the height it gives you.
What aspect ratio is a phone screen?
Most modern phones are around 19.5:9 or 20:9, which is taller than 16:9.
Is 4:3 better than 16:9?
Neither is better. 16:9 suits video and widescreens, while 4:3 shows more height and suits documents and many photos.
Sources and further reading
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Last reviewed: October 2026