Aspect ratio calculator
Change one number and get the other, so nothing ends up stretched.
Your dimensions
Type an original size, then change either new box. The other follows.
Result
How to use this aspect ratio calculator
- Choose a common ratio, or enter your original width and height.
- Enter your new width or new height.
- Read the matching dimension.
Who it is for
For designers, video editors and social media managers resizing assets for different platforms.
Why this matters beyond not squashing things
Knowing the ratio lets you put real width and height attributes on your
image tags. That is the single easiest fix for layout shift — the thing where you go to tap a
link and the page jumps because an image finally loaded above it.
The browser reads those two numbers, works out the shape, and reserves exactly the right space before the file arrives. Cumulative Layout Shift is one of the three Core Web Vitals, and this is most of the fix.
The ratios worth memorising
| Ratio | Pixels | Where |
|---|---|---|
| 1:1 | 1080 × 1080 | Square posts. Safe everywhere. |
| 4:5 | 1080 × 1350 | Instagram and Facebook feed. Most screen space. |
| 9:16 | 1080 × 1920 | Reels, Stories, TikTok, Shorts |
| 16:9 | 1920 × 1080 | YouTube, presentations, hero images |
| 1.91:1 | 1200 × 630 | Link previews on every platform |
Resize versus crop
They are different jobs and mixing them up is what produces stretched faces.
- Resizing keeps the shape and changes the size. Nothing is lost.
- Cropping changes the shape by cutting parts off.
If your target size is a different ratio, you must crop — there is no way to change the shape without either cutting something off or distorting it. The calculator above warns you when the size you have typed would distort.
Common questions
How do I calculate aspect ratio?
Divide the width and height by their largest common factor. 1920 × 1080 reduces to 16:9. To find a new height, multiply the new width by the height and divide by the original width.
What is an aspect ratio?
The relationship between width and height, written as two numbers. 16:9 means for every 16 across there are 9 down. It stays the same at any size.
Why do my images look stretched?
Because they are being displayed at a different ratio than they were made. Usually a CSS rule setting both width and height. Set one and let the other be auto, or use object-fit: cover.
Does this help my page speed score?
Indirectly and meaningfully. Putting real width and height attributes on images fixes layout shift, which is one of the three Core Web Vitals Google measures.
What size should I export for the web?
No wider than the space it will fill, then double it for high-resolution screens. A 600px wide slot wants a 1200px image — anything more is wasted bandwidth.
Need more customers as well?
This tool is free and always will be. If you also want ads, search and follow-up that bring in customers, I offer a free 45-minute consultation for businesses in the USA, UK, UAE, Australia and India.
Book a free consultationBuilt and maintained by Premkumar Ragav, an independent performance marketing specialist. Updated November 2026.