Design
Aspect Ratio Calculator
Scale image or video dimensions while keeping the correct aspect ratio.
Input
Set original ratio and fill either new width or new height.
Common Ratios
Original Size
×
↕
New Size (fill one)
=
Fill either new width or new height to auto-calculate the other value.
Output
Set dimensions to see scaled output size.
Frequently Asked Questions
What is an aspect ratio?
Aspect ratio is the proportional relationship between width and height, expressed as W:H. Common display ratios: 16:9 (widescreen HD video), 4:3 (traditional TV/monitor), 1:1 (square, Instagram), 21:9 (ultrawide cinema). Photography commonly uses 3:2 and 4:5.
How do I maintain aspect ratio in CSS?
Modern CSS: aspect-ratio: 16 / 9; on the element. Legacy technique: padding-top percentage trick (padding-top: 56.25% for 16:9, since 9/16 = 0.5625). The modern aspect-ratio property is supported in all current browsers and is the recommended approach.
How do I calculate the height of a 16:9 image given a width?
height = width × (9/16). For a 1920px wide image: 1920 × 9/16 = 1080px. For any ratio W:H and known dimension: unknown = known × (opposing dimension / same dimension). This tool performs these calculations instantly for any ratio.