A free aspect ratio calculator that simplifies any size, solves the missing side and draws the frame to scale.
Simplify any size to its ratio, solve the missing side, and see the frame drawn to scale.
Your numbers
Type a size, or pick a ratio. Then type a new width or height to get the other side at the same ratio.
Your result
Fill in the fields above to see your result.
Embed this tool on your site
Paste the code into any page: WordPress, Webflow, Squarespace, Ghost or plain HTML. It's free with the credit under it, which links back to navid.me.
This free aspect ratio calculator turns any width and height into its ratio, solves the missing side when you resize, and draws the frame to scale with the standard sizes that share it.
Type 1920 × 1080 and it says 16:9, then gives 720 for a width of 1280.
I built it because I resize thumbnails, Reels and slides every week, and a size that's off by a few pixels gets cropped or squashed. This makes the right size a 2-second job.
Here's how ratios work, a worked example, and the ratios you'll meet most.
TL;DRKey takeaways
What is an aspect ratio calculator?
An aspect ratio calculator finds the shape of a picture or screen: its width compared with its height. It also works out a new size that keeps that shape.
The ratio is the same whatever the size. A 1280 × 720 video and a 3840 × 2160 one are both 16:9.
How to use the aspect ratio calculator
You need a width and a height, or just a ratio.
Everything works in the browser, and the link shares the same sizes.
A worked example
Here's the example the calculator loads when you press Try an example: 1920 × 1080, resized to a width of 1280.
1920 and 1080 share a greatest common divisor of 120. 1920 ÷ 120 is 16 and 1080 ÷ 120 is 9, so the ratio is 16:9, or 1.78 to 1.
A width of 1280 at 16:9 needs a height of 1280 × 9 ÷ 16 = 720.
| Width | Height |
|---|---|
| 1280 px | 720 px |
| 1600 px | 900 px |
| 1920 px | 1080 px |
| 2560 px | 1440 px |
No size in the table has a fraction of a pixel on either side, so nothing gets rounded.
The ratios you'll meet most
These are the shapes most screens and posts use.
16:9, widescreen
TVs, laptop screens, YouTube videos and slides. The video resizer turns a vertical clip into it.
9:16, vertical video
Reels, Shorts and TikTok fill a phone screen at 9:16, often at 1080 × 1920.
4:5 and 1:1, feed posts
A 4:5 post (1080 × 1350) takes more of a phone's feed than a square 1:1 one. The image resizer crops a photo to either.
4:3, 3:2 and 21:9
4:3 is tablets and older screens, 3:2 is most camera photos, and 21:9 is ultrawide monitors and cinema.
Mistakes to avoid
These are the ways a resize goes wrong.
- Changing the width and the height by different amounts, which stretches the picture
- Rounding a height that should come out exact
- Uploading the right ratio at too small a size, which looks soft
- Forgetting the safe area where a platform's buttons cover the picture
For a thumbnail, the YouTube thumbnail downloader shows what a finished 16:9 one looks like.
Who is the aspect ratio calculator for?
It's for creators, designers and anyone resizing a picture, and these tools do the resizing.
- Image resizer – for photos at any size
- Video resizer – for videos in a new shape
- Post image generator – for share images at each platform's size
- Hex to RGB converter – for the colors in your design
- Compress image – for a smaller file at the same size
Get the ratio right first, and every resize after it is easy.
Plan your money with your AI
Take your numbers further in
Aspect Ratio Calculator FAQs
Questions about the aspect ratio calculator? Here's what to know.
An aspect ratio calculator finds a picture's width-to-height ratio and works out new sizes that keep it.
This free one also draws the frame to scale and lists standard sizes at the same ratio.
Divide the width and the height by their greatest common divisor.
1920 × 1080 divided by 120 is 16:9.
Multiply the new width by the ratio's height and divide by its width.
A width of 1280 at 16:9 needs a height of 720.
16:9, the widescreen ratio of HD video.
1280 × 720 and 3840 × 2160 are 16:9 too.
9:16, vertical video.
It's the shape of a phone screen held upright.
4:5, a tall portrait.
It's a common size for photo posts in a feed.
The width divided by the height.
16:9 is 1.78, and 4:3 is 1.33.
The picture either stretches or gets cropped.
Crop on purpose rather than stretching.
Yes, it's free with no sign-up.
It runs in your browser.
I did.
I'm Navid Moazzez, and I made the aspect ratio calculator as one of my free tools on navid.me.
More about me.
Navid Moazzez
AI business strategist & AI OS builder
Navid Moazzez helps creators and founders master AI and build their own AI Operating System (AI OS) to automate their business and life.
Navid.me is reader-supported. When you buy through links on this site, I may earn an affiliate commission. Learn more.
Related calculators
YouTube
More free tools
X
Bluesky
LinkedIn
Threads
Mastodon
Instagram
TikTok
Pinterest
Related MCP servers & CLIs
Substack
Apple Podcasts
Free AI newsletterThe most actionable AI newsletter for founders
Every week, get proven AI strategies, curated tools, and step-by-step systems to grow your audience, create better content, and build a profitable creator business.
No fluff, no filler, no BS. Just five minutes each week that might level up your online business and life.
P.S. Sign up now to get free access to my ultimate AI tools guide for creators.
