Aspect Ratio & Dimension Calculator
Calculate proportional dimensions for video, photos, and UI assets with a live reactive visual preview.
Frequently Asked Questions
How do I calculate the height for a given width and aspect ratio?▼
Multiply the width by the ratio's height and divide by its width. For 16:9 and a width of 1280, that is 1280 × 9 ÷ 16 = 720. Type either dimension and the other one is filled in for you.
How do I resize an image without stretching it?▼
Enter the original width and height as the ratio (for example 4000 and 3000), then type the new width or height you want. The other side is calculated so the proportions stay the same.
Which aspect ratio should I use for YouTube, Shorts, Reels or Instagram?▼
YouTube and most monitors use 16:9, Shorts and Reels use 9:16, Instagram feed portrait posts use 4:5, and square posts use 1:1. The preset buttons fill these in with one tap.
Does it handle decimal ratios like 2.39:1?▼
Yes. Cinema ratios such as 2.39:1 are used exactly as typed. Whole-number ratios are simplified automatically, so 1920:1080 is shown as 16:9.
Why are my pixel results rounded?▼
Pixels are whole numbers, so results are rounded to the nearest pixel. A ratio such as 2.39:1 at a width of 1920 gives 803 pixels, not 803.35.
Is my data sent to a server?▼
No. The calculator runs entirely in your browser, so nothing you enter is uploaded, stored or tracked. Once the page has loaded it keeps working without a connection.