Aspect Ratio Calculator
Calculate aspect ratio from dimensions and scale images/videos while maintaining ratio.
The Formula
New Height = New Width × Original Height / Original Width
New Width = New Height × Original Width / Original Height
Scale to width 1280:
Height = 1280 × 1080 / 1920
= 720px
Common Aspect Ratios
16:9: Standard widescreen HD/4K TV and most monitors, YouTube videos. 4:3: Traditional TV and older monitors. 1:1: Square, used for Instagram posts. 9:16: Vertical video for TikTok, Instagram Stories, Reels. 21:9: Ultra-wide cinema and gaming monitors. 3:2: Most DSLR cameras.
Frequently Asked Questions
What aspect ratio is best for YouTube?
16:9 is the standard for YouTube. Videos filmed in 4:3 get black bars on the sides (pillarboxing). Vertical 9:16 videos get black bars on top and bottom on a standard player but display full-screen on mobile YouTube Shorts. For standard YouTube uploads meant for desktop viewing, 16:9 at 1920×1080 (1080p) or 3840×2160 (4K) is ideal.
How do I maintain aspect ratio when resizing?
Divide the new desired width by the original width to get a scale factor. Multiply the original height by that same scale factor to get the new height. Or divide new height by original height and apply to width. This calculator does it automatically — enter the original dimensions and one new dimension, and it calculates the other to maintain the ratio exactly.
What does letterboxing and pillarboxing mean?
Letterboxing adds horizontal black bars (top and bottom) when content with a wider aspect ratio is displayed on a narrower screen — like a 21:9 film on a 16:9 TV. Pillarboxing adds vertical black bars (sides) when content with a narrower ratio is displayed on a wider screen — like 4:3 content on a 16:9 monitor. These bars preserve the original proportions rather than stretching or cropping the content.
What is the best aspect ratio for social media?
It depends on the platform. Instagram feed posts: 1:1 (square) or 4:5 (portrait). Instagram Stories and Reels: 9:16. Facebook feed: 1.91:1 or 1:1. Twitter/X: 16:9 for videos, 2:1 for images. TikTok: 9:16. LinkedIn: 1.91:1. For maximum flexibility across platforms, shooting in 4:5 portrait gives you content you can easily crop to 1:1, 9:16, or 16:9 in post-production.
What aspect ratio do iPhone photos use?
iPhones default to a 4:3 aspect ratio for standard photos (matching the sensor's native ratio). When shooting in portrait mode or with certain settings, photos may be 1:1. ProRAW photos capture the full sensor, which is 4:3. iPhones can also shoot video in 16:9 (standard), 9:16 (vertical/Cinematic), and with newer models, the sensor captures a slightly larger area allowing for more flexible post-production cropping.