Aspect Ratio Calculator

What this tool does

Aspect Ratio Calculator determines the proportional relationship between width and height, and scales dimensions while preserving that proportion. When you resize images or video, maintaining aspect ratio prevents stretching or squashing. Enter any dimensions and the calculator shows the simplified ratio (like 16:9 or 4:3) and computes proportionally scaled alternatives.

Beyond simple ratio display, the tool calculates new dimensions when you change either width or height while keeping the ratio locked. This is essential for creating multiple sizes of the same image, fitting content into different containers, or converting between formats without distortion.

How to use this tool

1. Enter original width and height values in the first row (W1 × H1).

2. View the automatically calculated aspect ratio in simplified form.

3. Enter a new width (W2) to calculate proportional height, or new height (H2) to calculate proportional width.

4. Alternatively, click ratio presets (16:9, 4:3, 1:1, etc.) to set common proportions.

5. Use the results for resizing, cropping, or planning layouts.

Common use cases

• Calculate video dimensions when scaling from 1080p to other resolutions
• Determine correct height when width is constrained by a layout
• Convert image dimensions for different social media platform requirements
• Plan responsive designs that maintain proportions across breakpoints
• Check if an image fits a target ratio before cropping
• Scale up or down while preserving original composition
• Calculate display sizes for monitors, TVs, and projectors
• Verify aspect ratios for film and video production formats

Key features and behavior

Ratio simplification

The calculator reduces dimensions to their simplest ratio using greatest common divisor math. A 1920×1080 image becomes 16:9; a 3000×2000 image becomes 3:2. This helps identify standard formats and compare proportions across different resolutions.

Proportional scaling

When you enter a new width or height, the other dimension calculates automatically to maintain the original ratio. Change width from 1920 to 1280, and height adjusts from 1080 to 720—the 16:9 proportion stays constant.

Common ratio presets

One-click presets for standard ratios: 16:9 (widescreen video), 4:3 (traditional TV/monitors), 3:2 (classic photography), 1:1 (square), 21:9 (ultrawide), 9:16 (vertical video), 2:3 (portrait photo). Presets help when targeting specific platform requirements.

Orientation detection

The calculator identifies whether dimensions represent landscape (width > height), portrait (height > width), or square (equal) orientation. This helps verify you haven't accidentally swapped values.

Tips and limitations

• Non-standard ratios display as decimals (e.g., 1.78:1 for 16:9 with complex dimensions)
• Pixel values must be integers; fractional results round to nearest whole pixel
• Aspect ratio applies to any unit (pixels, inches, centimeters) consistently
• Changing one dimension then the other breaks the link; start fresh to maintain ratio
• Some dimensions don't simplify nicely (1366×768 ≈ 683:384, displayed as decimal)
• The tool calculates ratios but doesn't perform actual image resizing

FAQ

What does aspect ratio mean?

Aspect ratio expresses the proportional relationship between width and height. A 16:9 ratio means for every 16 units of width, there are 9 units of height. This proportion stays constant regardless of actual size—both 1920×1080 and 3840×2160 are 16:9.

Why is aspect ratio important?

Displaying content at the wrong aspect ratio causes distortion—circles become ovals, squares become rectangles. Maintaining correct ratio ensures images and videos look as intended without stretching or squashing.

What's the most common aspect ratio?

16:9 dominates modern displays: HDTV, computer monitors, and most smartphones in landscape. 4:3 was standard for older TVs and remains common in tablets. 1:1 (square) is popular for social media. 3:2 is traditional for photography.

How do I find an image's aspect ratio?

Divide width by height. A 1920×1080 image: 1920÷1080 = 1.778, which equals 16÷9. Or enter dimensions in this calculator to see the simplified ratio automatically.

Can I convert between different aspect ratios?

Changing aspect ratio requires either cropping (removing content from edges) or adding letterboxing/pillarboxing (black bars). You can't change ratio without affecting content or adding blank space. This calculator helps plan such conversions.

What aspect ratio should I use for Instagram?

Instagram supports multiple ratios: 1:1 (square, traditional), 4:5 (portrait, recommended for maximum feed visibility), 16:9 (landscape). Stories use 9:16 (vertical full-screen).

Why doesn't my ratio simplify to a nice number?

Some dimension combinations don't have clean integer ratios. A 1366×768 screen has an unusual ratio (≈1.78:1) because those specific numbers don't share common factors that produce simple integers. The decimal representation is equally valid.

How do I maintain aspect ratio when resizing images?

Lock one dimension and calculate the other using this tool, then use those exact values in your image editor. Most software also has an "aspect ratio lock" option that does this automatically.