Aspect Ratio Calculator

Enter a width and height to calculate the simplified aspect ratio, decimal ratio, orientation, total pixels, and matching dimensions. All calculations run locally in your browser.

What Is an Aspect Ratio?

An aspect ratio describes the proportional relationship between the width and height of an image, video, screen, or design canvas.

It is usually written as two numbers separated by a colon, such as:

• 16:9
• 4:3
• 1:1
• 4:5
• 9:16

The first number represents the width, and the second number represents the height.

For example, a 1920 × 1080 video has an aspect ratio of 16:9. A 3840 × 2160 video also has a 16:9 aspect ratio, even though it contains four times as many pixels.

Aspect ratio describes shape, not resolution.

How to Use the Aspect Ratio Calculator

1. Enter the width of your image, video, or canvas.
2. Enter the height.
3. Select one of the suggested target widths or enter a custom width.
4. Select Calculate.
5. Review the simplified ratio, decimal ratio, orientation, pixel count, and matching dimensions.

You can reverse the width and height values with the swap button when changing between landscape and portrait formats.

Use Reset to return the calculator to its default values.

How Aspect Ratio Is Calculated

The calculator simplifies the width and height by dividing both values by their greatest common divisor.

For a 1920 × 1080 image:

Greatest common divisor: 120

1920 ÷ 120 = 16
1080 ÷ 120 = 9

Simplified aspect ratio: 16:9

The decimal ratio is calculated as:

Decimal ratio = Width ÷ Height

For 1920 × 1080:

1920 ÷ 1080 = 1.7778

The decimal result is displayed to a maximum of four decimal places.

How Matching Dimensions Are Calculated

To calculate a new height while preserving the original aspect ratio:

New height = New width × Original height ÷ Original width

For example, if a 1920 × 1080 video is resized to a width of 1280 pixels:

New height = 1280 × 1080 ÷ 1920
New height = 720 pixels

The matching dimensions are therefore:

1280 × 720

When a calculation produces a fractional pixel value, the result is rounded to the nearest whole pixel.

Common Image and Video Aspect Ratios

Some screen resolutions marketed as “21:9” are only approximate matches for the mathematical 21:9 ratio.

16:9 Widescreen Format

The 16:9 ratio is one of the most widely used formats for online video, television, presentations, and computer displays.

Common 16:9 dimensions include:

• 1280 × 720
• 1920 × 1080
• 2560 × 1440
• 3840 × 2160
• 7680 × 4320

YouTube uses 16:9 as the standard aspect ratio for videos displayed on desktop players. Other ratios can still be uploaded, but the player may adapt by adding padding or changing its display area.

9:16 Vertical Video Format

The 9:16 ratio is the portrait version of 16:9. It is commonly used for full-screen mobile content, including short-form videos and stories.

Common 9:16 dimensions include:

• 720 × 1280
• 1080 × 1920
• 1440 × 2560
• 2160 × 3840

A vertical 1080 × 1920 video contains the same number of pixels as a horizontal 1920 × 1080 video. Only the orientation is different.

4:5 Portrait Format

The 4:5 ratio is frequently used for portrait images and videos in social media feeds.

A common size is:

1080 × 1350

Because the format is taller than a square image, it can occupy more vertical space in a mobile feed without requiring a full-screen 9:16 layout.

1:1 Square Format

A 1:1 ratio means the width and height are identical.

Examples include:

• 800 × 800
• 1080 × 1080
• 2000 × 2000

Square formats are useful when a design must work consistently across multiple layouts or when the available display area is approximately equal in width and height.

Aspect Ratio vs. Resolution

Aspect ratio and resolution are related, but they describe different properties.

Aspect ratio describes the proportional shape of the content.

Resolution describes the number of pixels used to create it.

For example:

All three resolutions have the same shape, but they contain different amounts of visual information.

A higher resolution does not automatically change the aspect ratio.

Avoiding Stretched Images and Videos

Stretching occurs when the width or height is changed without preserving the original ratio.

For example, resizing a 1920 × 1080 image to 1000 × 1000 changes it from 16:9 to 1:1. If the original image is forced into the new dimensions, people and objects may appear unnaturally narrow or wide.

To avoid distortion:

• Change one dimension and calculate the other.
• Crop the content to the target ratio.
• Add padding around the content.
• Use a responsive container that preserves the ratio.

The matching-dimensions result from this calculator can help you resize content without stretching it.

Cropping, Letterboxing, and Pillarboxing

When the source ratio does not match the destination ratio, the content must usually be cropped, padded, or stretched.

Cropping removes part of the image or video so that it fills the destination frame.

Letterboxing adds horizontal bars above and below the content.

Pillarboxing adds vertical bars on the left and right sides.

Cropping usually creates a more immersive result, but it can remove important details near the edges. Padding preserves the complete image but leaves unused space around it.

Choosing an Aspect Ratio for Social Media

The ideal ratio depends on the platform and placement.

Typical formats include:

• 16:9 for standard landscape video
• 1:1 for square feed content
• 4:5 for portrait feed content
• 9:16 for full-screen vertical content

Meta supports different ratios depending on placement, including 1:1, 4:5, 16:9, and 9:16. TikTok recommends 9:16 for vertical in-feed video. LinkedIn video advertising supports landscape, square, vertical, and portrait formats.

Platform requirements can change. Always confirm the current specifications before exporting a final campaign or production asset.

Calculation Accuracy

OutputMath uses the integer dimensions entered into the calculator to produce an exact simplified ratio.

The calculator:

• Accepts dimensions from 1 to 1,000,000
• Simplifies ratios using the greatest common divisor
• Rounds decimal ratios to four decimal places
• Rounds matching dimensions to the nearest whole pixel
• Calculates the total pixel count from width × height
• Performs all calculations inside your browser

No image or video upload is required.

Frequently Asked Questions

What aspect ratio is 1920 × 1080?

1920 × 1080 simplifies to 16:9. It is commonly known as Full HD or 1080p resolution.

What aspect ratio is 3840 × 2160?

3840 × 2160 also simplifies to 16:9. This resolution is commonly associated with 4K UHD video.

What aspect ratio is 1080 × 1350?

1080 × 1350 simplifies to 4:5. It is a common portrait format for social media feed content.

What aspect ratio is 1080 × 1920?

1080 × 1920 simplifies to 9:16. It is widely used for vertical mobile video, stories, and short-form content.

Can different resolutions have the same aspect ratio?

Yes. For example, 1280 × 720, 1920 × 1080, and 3840 × 2160 all use a 16:9 ratio.

Does aspect ratio affect file size?

Not directly. File size is more strongly affected by pixel dimensions, video duration, bitrate, compression, frame rate, color information, and file format.

However, changing an aspect ratio may also change the total number of pixels, which can affect file size.

How do I resize an image without stretching it?

Keep the original aspect ratio and calculate the matching width or height. You can also crop the image if the destination requires a different ratio.

Why does the calculator show a custom ratio?

A custom ratio means the dimensions do not closely match one of the common formats recognized by the calculator. This is normal for cropped images, browser screenshots, custom canvases, and irregular exports.

Are my dimensions uploaded to a server?

No. The calculation runs locally in your browser. The calculator does not need to upload your image, video, or dimensions to perform the calculation.