Aspect Ratio Calculator

What Is an Aspect Ratio?

An aspect ratio describes the proportional relationship between the width and height of an image, screen, video, or display. It is written as two numbers separated by a colon — for example, 16:9 means there are 16 units of width for every 9 units of height.

Aspect ratios appear everywhere in digital media:

• Video and TV: 16:9 for HD/4K, 4:3 for old television, 9:16 for mobile vertical video
• Photography: 3:2 for 35mm film and DSLRs, 4:3 for many compact cameras
• Social media: 1:1 square for Instagram, 9:16 for TikTok and Reels
• Cinema: 21:9 and even wider for movies in theaters
• Web design: Various ratios for hero images, thumbnails, and Open Graph images

How to Use the Aspect Ratio Calculator

Calculate a Ratio

1. Enter your Width and Height in pixels
2. The simplified aspect ratio appears instantly — for example, 1920×1080 simplifies to 16:9
3. The decimal equivalent (width ÷ height) is shown below for easy comparison

Scale Dimensions with Lock

1. Enter your original dimensions (e.g., 1920×1080)
2. Click Lock to enable proportional scaling
3. Change either width or height — the other dimension updates automatically
4. Example: lock 1920×1080, change width to 1280 → height automatically becomes 720

Use Ratio Presets

Click any ratio preset button (16:9, 4:3, 1:1, etc.) to apply that ratio to your current width. The height adjusts automatically to match the selected ratio.

Compare Two Ratios

Use the Compare Ratios section to see whether two ratio pairs are equivalent:

• Enter Ratio A and Ratio B as width:height pairs
• The tool shows the simplified form of each ratio
• If they are equivalent (same simplified form), a confirmation message appears
• If different, the tool shows which ratio is wider and the decimal values

Calculate Screen Diagonal

Enter a PPI (pixels per inch) value to calculate the physical screen diagonal for your current dimensions:

• The formula is: diagonal = √((width/PPI)² + (height/PPI)²)
• Common PPI values: 72–96 for desktop monitors, 200–400+ for smartphones
• Results show diagonal, width, and height in inches

Common Aspect Ratios

Standard Resolutions and Their Ratios

How Aspect Ratio Simplification Works

Aspect ratios are simplified using the Greatest Common Divisor (GCD):

1. Calculate GCD of width and height
2. Divide both by the GCD

Example: 1920×1080

• GCD(1920, 1080) = 120
• 1920 ÷ 120 = 16
• 1080 ÷ 120 = 9
• Result: 16:9

Example: 1200×630

• GCD(1200, 630) = 30
• 1200 ÷ 30 = 40
• 630 ÷ 30 = 21
• Result: 40:21 (not a standard named ratio, but this is the correct simplified form)

How to Maintain Aspect Ratio When Resizing

To scale an image while maintaining its aspect ratio, use the following formulas:

Given new width, find height:

new_height = new_width × (original_height / original_width)

Given new height, find width:

new_width = new_height × (original_width / original_height)

Example: Scale 1920×1080 to 1280 wide:

new_height = 1280 × (1080 / 1920) = 1280 × 0.5625 = 720
Result: 1280×720

This is exactly what the Lock feature does automatically.

Aspect Ratio vs Resolution

These terms are often confused:

• Aspect ratio is the proportion of width to height (16:9). Multiple resolutions can share the same ratio.
• Resolution is the exact pixel count (1920×1080). It determines sharpness and file size.

A 4K monitor (3840×2160) and an HD monitor (1920×1080) both have a 16:9 aspect ratio, but very different resolutions. Content filmed in 16:9 displays correctly on both without cropping.

Aspect Ratios for Social Media (2024)

Frequently Asked Questions

How do I convert a ratio to pixels? Multiply both parts of the ratio by the same number. For 16:9 at 1080 height: 9 × 120 = 1080, so 16 × 120 = 1920. The result is 1920×1080.

What ratio is a standard letter-size page? US Letter (8.5×11 inches) has a ratio of approximately 17:22 or 0.773:1. A4 paper (210×297 mm) has a ratio of approximately 1:√2 (1:1.414), simplifying to approximately 210:297 = 70:99.

Is 16:9 the same as 1920:1080? Yes, 1920:1080 simplifies to 16:9 — both represent the same aspect ratio. Any resolution that simplifies to 16:9 (1280×720, 2560×1440, 3840×2160) shares the same ratio.

What does PPI mean and how do I find my screen’s PPI? PPI (pixels per inch) is the density of pixels on a screen. To calculate PPI: PPI = diagonal_pixels / diagonal_inches. For a 24-inch monitor at 1920×1080: diagonal pixels = √(1920² + 1080²) ≈ 2203 pixels. PPI = 2203 / 24 ≈ 91.8. Common values: 72–96 for desktop monitors, 100–200 for laptops, 250–500+ for smartphones.

Why does my video look stretched or letterboxed? Stretching occurs when the player aspect ratio does not match the video content ratio. Letterboxing (black bars on top/bottom) appears when widescreen content (16:9) plays in a 4:3 container. Pillarboxing (bars on sides) occurs when 4:3 content plays in a 16:9 container. Use the correct source ratio to avoid distortion.

Does the tool work offline? Yes. All calculations use simple math (GCD, division, Pythagorean theorem) and run entirely in your browser with no network requests required.