Aspect Ratio Calculator
Calculate aspect ratios for video, images and screens. Find missing width or height from any ratio (16:9, 4:3, 21:9, custom). Convert between ratios and pixel dimensions.
How to use
Standard video ratios
16:9 is the standard for YouTube, Netflix, and modern TV. 9:16 is used for TikTok, Reels, and Shorts. 21:9 is cinematic ultra-wide. 1:1 is square (Instagram posts).
How to find the missing dimension
Enter your known width and the target ratio. The height is calculated as: height = (width ÷ ratio_width) × ratio_height. For 1200px wide at 16:9: 1200 ÷ 16 × 9 = 675px.
The golden ratio (approximately 1.618:1) appears throughout nature and has been used in art and architecture for millennia. A 1920×1187 frame is almost exactly the golden ratio — though almost no camera sensor uses it.
Frequently asked questions
What aspect ratio is used for YouTube and most online video?
16:9 is the standard aspect ratio for YouTube, Netflix, and most modern screens. It replaced 4:3 (the old TV format) as the standard because it better matches how human vision works — we see wider than we see tall. A 1920×1080 HD frame is 16:9, as is 3840×2160 (4K UHD).
What is the 9:16 aspect ratio used for?
9:16 is 16:9 rotated vertically — it's the aspect ratio of a smartphone held in portrait orientation. It's the standard format for TikTok, Instagram Reels, YouTube Shorts, and Snapchat. A 1080×1920 frame is 9:16.
How do I calculate the height from a width and aspect ratio?
Divide the width by the ratio's first number, then multiply by the second number. For example, for a 1200px wide image at 16:9: 1200 ÷ 16 = 75, then 75 × 9 = 675px height. Or use this calculator and just enter the width and ratio.