Aspect Ratio CalculatorCalculate aspect ratios from dimensions and resize images/videos while maintaining proportions.
Aspect Ratio Calculator
Calculate aspect ratios from dimensions and resize images/videos while maintaining proportions.
Enter Dimensions
Input width and height in pixels (or use a preset ratio).
Optional: Resize
Enter a new width or height to maintain the ratio.
View Ratio
See the simplified ratio, decimal value, and resized dimensions.
What Is Aspect Ratio Calculator?
The Aspect Ratio Calculator determines the aspect ratio of any image, video, or screen from its width and height dimensions. It simplifies the ratio to its lowest terms (e.g., 1920×1080 → 16:9), shows the decimal equivalent, and can resize dimensions while maintaining the same ratio. Quick-select buttons for common ratios (16:9, 4:3, 21:9, 1:1, 9:16) make it easy to work with standard formats. The resize mode lets you enter a new width or height to automatically calculate the matching dimension.
Why Use Our Aspect Ratio Calculator?
- Simplifies dimensions to lowest-terms aspect ratio
- Resize mode maintains proportions automatically
- Quick presets for common ratios (16:9, 4:3, 21:9, 1:1)
- Shows both ratio and decimal format
Common Use Cases
Image Editing
Calculate proper crop dimensions for social media and print.
Video Production
Ensure video exports match target aspect ratios.
Web Design
Calculate responsive container sizes that maintain aspect ratios.
Display Selection
Compare monitor and TV aspect ratios.
Technical Guide
The aspect ratio is computed by finding the GCD (Greatest Common Divisor) of width and height, then dividing both by the GCD: Ratio = (W/GCD) : (H/GCD). The GCD is found using the Euclidean algorithm. The decimal ratio = W/H. For resizing with locked width: New Height = New Width / (W/H). For locked height: New Width = New Height × (W/H). Common aspect ratios: 16:9 (widescreen), 4:3 (classic TV), 21:9 (ultrawide), 1:1 (square), 9:16 (mobile portrait), 3:2 (35mm film), 2.39:1 (cinema scope).
Tips & Best Practices
- 1Most modern screens use 16:9. Ultra-wide monitors use 21:9
- 2Social media platforms have specific recommended aspect ratios for posts and stories
- 3When resizing, always lock to one dimension to avoid distortion
- 4Instagram uses 1:1 (square), 4:5 (portrait), and 1.91:1 (landscape)
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Math & CalculatorsFrequently Asked Questions
QWhat is the most common aspect ratio?
QWhat aspect ratio is 1920×1080?
QWhat aspect ratio does Instagram use?
QHow do I resize without distortion?
QWhat is the difference between 16:9 and 16:10?
About Aspect Ratio Calculator
Aspect Ratio Calculator is a free online tool from FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration required. No ads. Just fast, reliable tools.