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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.
The Aspect Ratio Calculator is a free online tool. Enter any two values — width, height, or ratio — and it instantly calculates the third. Covers all standard video ratios (16:9, 4:3, 21:9, 1:1, 9:16) and accepts custom ratios.
Aspect Ratio
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How to use
1
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).
2
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.
💡 Did you know?
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.
Reviewed for 2026. Built by a UK-based qualified primary teacher and FA Level 2 coach as part of 247QuickTools' free utility-tools project.