How do I calculate a video aspect ratio?
Divide the width by the height, then reduce both numbers by their greatest common divisor. For example, 1920 by 1080 reduces to 16:9.
Video Aspect Ratio Calculator
Reduce pixel dimensions to a ratio, recognise common video formats, and calculate a matching height for any new width.
Reduced ratio
16:9
Decimal ratio: 1.7778
Scaled dimensions
1280 × 720
Matches 16:9: YouTube, landscape video, HDTV.
Common video aspect ratios
16:9
YouTube, landscape video, HDTV
9:16
Shorts, Reels, TikTok, Stories
1:1
Square social posts
4:5
Portrait feed posts
4:3
Classic television and presentations
21:9
Ultrawide and cinematic framing
How the calculation works
The simplified ratio divides both source dimensions by their greatest common divisor. Scaling uses new height = new width × original height ÷ original width. Rounding to even pixels avoids dimension errors in encoders that process colour information in two-pixel blocks.
Changing the canvas to a different ratio requires cropping, padding, or reframing. Simply forcing a 16:9 image into 9:16 dimensions will stretch people and objects.
Frequently asked questions
How can I resize a video without stretching it?
Keep the same width-to-height ratio. Enter the original dimensions and a new width; the calculator returns the matching height. If an encoder requires even-numbered dimensions, enable the even-pixel option.
What is the aspect ratio for vertical video?
Full-screen vertical video commonly uses 9:16, such as 1080 by 1920 pixels. A 4:5 ratio is also common for portrait posts that remain inside a feed.