Aspect Ratio Calculator
Calculate aspect ratios and resize dimensions. Keep proportions when resizing images or videos. Free online aspect ratio calculator.
px
px
16:9(1.7778)
px
px
New ratio: 16:9(Proportional to 16:9)
1280 x 720
🔒 Fast, free math calculators that run in your browser. No uploads, 100% private.
Last updated: January 2026
Related Calculators
Frequently Asked Questions
What is aspect ratio?
Aspect ratio is the proportional relationship between width and height, expressed as width:height. A 16:9 ratio means for every 16 units of width, there are 9 units of height. Common examples: 1920×1080 is 16:9, 1080×1080 is 1:1 (square). Aspect ratio stays constant when you resize proportionally—a 1920×1080 image scaled to 1280×720 is still 16:9.
What aspect ratio should I use for social media?
Each platform has optimal ratios: Instagram feed is 1:1 (square) or 4:5 (portrait); Stories/Reels are 9:16 (vertical); YouTube thumbnails and videos are 16:9; TikTok is 9:16; Twitter posts work best at 16:9 or 2:1 for headers; LinkedIn prefers 1.91:1. Using the wrong ratio results in cropping or black bars.
How do I resize without distorting my image?
To resize proportionally, only change one dimension (width or height) and calculate the other. Formula: New Height = Original Height × (New Width ÷ Original Width). Example: 1920×1080 resized to 1280 width → 1280 × (1080÷1920) = 720 height. The calculator does this automatically when you lock the aspect ratio.
What's the difference between 16:9 and 4:3?
16:9 is widescreen (HD standard since 2009)—used for modern TVs, YouTube, most monitors. 4:3 is the older 'fullscreen' format from CRT TVs and early computer monitors. 4:3 is taller/narrower, better for documents and some photography. 16:9 is wider, better for cinematic content and landscapes.
How do I find the aspect ratio of an image?
Divide width by height, then simplify. For 1920×1080: 1920÷1080 = 1.777... which equals 16÷9. The greatest common divisor (GCD) method works too: GCD(1920,1080) = 120, so 1920÷120 : 1080÷120 = 16:9. For non-standard dimensions like 1500×900, divide both by GCD(1500,900)=300 to get 5:3.