🔢 Aspect Ratio Calculator
Common Aspect Ratios
Enter ONE known dimension to find the other
📐 Result
Ratio
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aspect ratio
Width
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pixels
Height
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pixels
Decimal
—
w ÷ h
📺 Visual Preview
16:9
Enter the width and height of your image or screen to find its simplified aspect ratio.
📐 Aspect Ratio Result
Simplified Ratio
—
aspect ratio
Decimal
—
w ÷ h
GCD
—
greatest common divisor
Percentage
—
width/height %
📺 Visual Preview
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Common Match: —
Compare two aspect ratios side by side. Enter dimensions or ratios for both.
📦 Ratio A
📦 Ratio B
⚖️ Comparison Result
Ratio A
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—
VS
Ratio B
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—
—
Visual Comparison (scaled to same width)
Ratio A
Ratio B
📋 Common Aspect Ratios Reference
| Ratio | Decimal | Common Name | Use Cases |
|---|---|---|---|
| 16:9 | 1.778 | Widescreen HD | YouTube, TV, Monitors, Presentations |
| 4:3 | 1.333 | Standard | Old TV, Cameras, iPad (classic) |
| 1:1 | 1.000 | Square | Instagram Post, Profile Photos |
| 3:2 | 1.500 | Classic Photo | DSLR Photos, 35mm Film, Prints |
| 21:9 | 2.333 | Ultrawide | Ultrawide Monitors, Cinematic |
| 9:16 | 0.563 | Portrait | Instagram Stories, TikTok, Reels |
| 5:4 | 1.250 | Near Square | Early Monitors, Medium Format |
| 2:1 | 2.000 | Univisium | Twitter Header, Modern Cinema |
📖 How to Use the Aspect Ratio Calculator
- Choose a tab: Select "Find Dimension" to calculate a missing width or height, "Find Ratio" to simplify dimensions into a ratio, or "Compare Ratios" to compare two sizes.
- Enter your values: For "Find Dimension", pick a preset ratio (like 16:9) or type custom ratio values, then enter either the known width or height.
- Click Calculate: Hit the blue button to instantly see the result, including the missing dimension, decimal ratio, and a visual preview.
- Use the visual preview: The rectangle preview updates to show you exactly what your aspect ratio looks like, making it easy to compare proportions.
- Reference the table: Scroll down to the common ratios table for quick reference on which ratio suits your use case (social media, video, print, etc.).
About the Aspect Ratio Calculator
An aspect ratio calculator is an essential tool for designers, photographers, videographers, and developers who need to maintain consistent proportions across different image sizes and screen resolutions. Whether you're working with a 16:9 calculator for widescreen video, adapting a design for mobile (9:16), or finding the perfect dimensions for print media, understanding image aspect ratio is fundamental.
This free online tool helps you calculate missing dimensions when resizing images without distortion, find the simplified screen aspect ratio for any resolution, and compare two different ratios side by side. It supports all common ratios including 16:9 (HD video), 4:3 (classic TV), 1:1 (Instagram), 3:2 (DSLR), and any custom ratio you need.
The aspect ratio is calculated using the Greatest Common Divisor (GCD) method to simplify ratios to their lowest terms. For example, a 1920×1080 pixel image simplifies to a 16:9 aspect ratio because both 1920 and 1080 are divisible by 120, giving 16 and 9 respectively.
❓ Frequently Asked Questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between the width and height of an image, video, or screen. It is expressed as two numbers separated by a colon, such as 16:9 or 4:3. For example, a 16:9 ratio means for every 16 units of width, there are 9 units of height — regardless of the actual pixel dimensions. A 1280×720px and a 1920×1080px image both have a 16:9 aspect ratio.
What is the most common aspect ratio for videos?
The most common aspect ratio for modern videos and screens is 16:9, which is the standard widescreen format used by YouTube, Netflix, HDTVs, and most computer monitors. Before widescreen became mainstream, 4:3 was the standard for television and older computer monitors. For vertical/mobile video (TikTok, Instagram Reels), the 9:16 portrait ratio is most common.
How do I calculate a missing dimension using aspect ratio?
To find the missing dimension, you use simple proportion math. If the ratio is W:H and you know the width, then: Height = (Known Width × Ratio H) ÷ Ratio W. For example, with a 16:9 ratio and width of 1920px: Height = (1920 × 9) ÷ 16 = 1080px. Similarly, if you know the height: Width = (Known Height × Ratio W) ÷ Ratio H. Our calculator handles this automatically — just enter one dimension and click Calculate.
What aspect ratio should I use for social media images?
Different platforms have different recommended aspect ratios. Instagram Feed Posts: 1:1 (square) or 4:5 portrait. Instagram Stories & Reels: 9:16. Facebook cover photo: approximately 2.7:1. Twitter/X header: 3:1. YouTube thumbnail: 16:9. LinkedIn banner: approximately 4:1. Pinterest: 2:3 (vertical). Always check each platform's current guidelines as they may update their recommendations.
How do I simplify an aspect ratio?
To simplify an aspect ratio, find the Greatest Common Divisor (GCD) of the width and height, then divide both numbers by the GCD. For example, for a 1920×1080 image: the GCD of 1920 and 1080 is 120. So 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, giving you the simplified ratio 16:9. The GCD can be found using the Euclidean algorithm, which is what our "Find Ratio" calculator uses automatically.