Aspect Ratio Calculator for Resizing Images and Video
Enter any 3 of width and height and the calculator solves the 4th to keep the ra...Enter any 3 of width and height and the calculator solves the 4th to keep the ratio. Presets, custom ratios, the simplified ratio and a live preview, ...
Updated
Aspect ratio
Type any custom ratio like 21:9, or pick a preset below. These two numbers set the proportion.
New size
Preset aspect ratios
Common 16:9 resolutions
Quick answer
To calculate an aspect ratio, divide the width by the height and reduce it to whole numbers, so 1920x1080 becomes 16:9. To resize while keeping that ratio, enter the original width and height, then type only the new width and the calculator solves the matching height (1280 wide gives 720 tall). YaliKit's calculator does the reduction and the solve live in your browser, with presets, a custom-ratio mode and a visual preview, and nothing is uploaded.
Everything In One Place
Why Use Aspect Ratio Calculator for Resizing Images and Video?
Solve The Missing Dimension
Fill any three of the four boxes (original width, original height, new width, new height) and the calculator solves the fourth so the image keeps the exact same proportions. Change the new width and the height follows, or the other way around.
Link Ratio, No Distortion
The link toggle locks the proportion while you resize, so a resized photo or video never stretches or squashes. Turn it off to edit each dimension freely when you want an intentional change.
Presets And Custom Ratios
One click fills 16:9, 4:3, 1:1, 21:9, 9:16, 3:2 and more. Or type your own ratio like 2.35:1 in the aspect fields. The simplified ratio and decimal update the moment you type.
100% Private, In Your Browser
Every calculation is plain arithmetic running locally, the same GCD-reduce and solve helpers our tools are unit tested against. Nothing is uploaded, so it is instant and works offline.
What You Can Do
Video Production
Size footage for YouTube (16:9), Reels and TikTok (9:16) or cinema (21:9) without black bars or stretching.
Resizing Images
Scale a photo to a new width and get the exact height that keeps it sharp and undistorted.
Social Media Posts
Match Instagram (1:1 or 4:5), Pinterest (2:3) and Story (9:16) sizes before you export.
Web And UI Design
Keep hero images, thumbnails and cards on a consistent ratio across breakpoints.
How It Works
Enter The Original Size Or Ratio
Type the original width and height (for example 1920 and 1080), or click a preset like 16:9. This sets the proportion the calculator will keep.
Type One New Dimension
Enter the new width you want, say 1280, and the new height solves to 720 automatically. Or type the height and let the width follow. Keep the link toggle on to hold the ratio.
Read And Copy
See the simplified ratio (16:9), the decimal (1.7778), megapixels and a live preview box. Copy the ratio or the new size with one click and paste it into your editor.
Pro Tips
Match Your Platform First
Pick the target platform's ratio before you set pixels. YouTube is 16:9, an Instagram feed is 1:1 or 4:5, and Reels and TikTok are 9:16. Choosing the ratio first avoids re-cropping later.
Keep The Link On To Avoid Stretching
Leave the link toggle on whenever you resize a real image or video. It holds the proportion so faces and shapes stay natural instead of squashing.
Ratio Is Not Resolution
16:9 is a shape, not a size. 1280x720 and 3840x2160 are both 16:9. Use the ratio to keep proportions, then read the resolution when you need the exact pixel count for export.