myAspect Ratio Calculator
Maintain aspect ratios when scaling images, videos, or designs. Enter any dimension to calculate the other.
Common ratios
Scale dimensions
px
px
16:9
Simplified ratio
1.778
Ratio as decimal
2.07 MP
Megapixels
1080p / Full HD
Common name
Common aspect ratios reference
- 16:9 — HD and UHD video, YouTube, most monitors (1920×1080, 3840×2160)
- 4:3 — Legacy SD television, many tablets (1024×768)
- 1:1 — Square, Instagram posts, album art
- 21:9 — Ultrawide cinema displays, cinematic film
- 9:16 — Vertical video, mobile-first content (TikTok, Instagram Stories)
- 3:2 — DSLR cameras, 35mm film, many laptop screens
Standard aspect ratios and their uses
Aspect ratio is the proportional relationship between width and height, expressed as W:H. Choosing the right aspect ratio ensures images and videos display correctly without distortion, cropping, or letterboxing across different screens and platforms.
- 16:9 — widescreen standard for video, YouTube, HD and 4K monitors, presentations
- 4:3 — traditional TV and monitor format, still common for document scans and some cameras
- 1:1 — square format used by Instagram, avatar images, and some print formats
- 9:16 — portrait video for Stories, Reels, TikTok, and smartphone full-screen content
- 3:2 — standard DSLR/mirrorless camera sensor ratio, 35mm film format
Frequently Asked Questions
About the Aspect Ratio Calculator
What is aspect ratio?
Aspect ratio is the proportional relationship between a rectangle's width and height, expressed as W:H. Common ratios include 16:9 (widescreen video), 4:3 (traditional TV), and 1:1 (square).
How to use this calculator
Enter any two known values — such as width and ratio, or height and ratio — and the missing dimension is calculated instantly. Useful for resizing images, planning video exports, or designing layouts.
- 16:9 — standard widescreen (YouTube, HD, 4K)
- 4:3 — classic TV and older monitors
- 1:1 — square format (Instagram posts)
- 21:9 — ultrawide cinema and monitors
- 9:16 — vertical video (mobile, Reels, TikTok)
Related tools
What is aspect ratio?
An aspect ratio is the proportional relationship between an image's width and height, expressed as two numbers separated by a colon. For example, 16:9 means for every 16 units of width there are 9 units of height. It describes the shape of a frame, not its size.
Why is 16:9 so common?
16:9 (widescreen) became the standard for HD television, computer monitors, and online video platforms because it makes efficient use of the horizontal space in our peripheral vision. YouTube, Netflix, and most modern displays use 16:9.
What ratio is best for social media?
Different platforms prefer different ratios: Instagram square posts use 1:1, Instagram portrait stories use 9:16, Twitter/X recommended images use 16:9, Facebook covers use 16:9, and Pinterest favours 2:3 (portrait).
How do I maintain aspect ratio in CSS?
Modern CSS: use the aspect-ratio property.
img { aspect-ratio: 16/9; width: 100%; }. For older browser support, use the padding trick: a container with padding-top: 56.25% (9/16 = 56.25%) and position:absolute on the child. The CSS aspect-ratio property is now supported in all modern browsers.What aspect ratio is best for social media videos?
16:9 (1920x1080) for YouTube, Twitter/X videos, and LinkedIn. 9:16 (1080x1920) for Instagram Reels, TikTok, and YouTube Shorts. 1:1 (1080x1080) for Instagram feed posts and some Twitter posts. 4:5 (1080x1350) for Instagram portrait posts. Facebook supports 16:9, 1:1, and 4:5.