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Aspect Ratio Calculator

Video Calculator

Aspect Ratio Calculator

Simplify a pixel aspect ratio and calculate proportional resize dimensions, total pixels, and megapixels.

Calculate aspect ratio and resize dimensions

Simplified ratio16:9
Resized dimensions1280 x 720 px
Original pixels2,073,600
Original megapixels2.07 MP

The missing resize dimension is rounded to the nearest whole pixel while preserving the original ratio as closely as possible.

How to use the aspect ratio calculator

Enter the original pixel width and height, choose whether you know the new width or new height, and enter that target dimension. The calculator simplifies the original ratio and calculates the missing resize dimension.

Aspect ratio formulas

Aspect ratio = width : height; new height = new width x original height / original width

When resizing by height, the inverse formula calculates new width. The ratio is simplified by dividing both original dimensions by their greatest common divisor. The missing dimension is rounded to the nearest whole pixel.

Worked example

A 1920 x 1080 frame reduces to a 16:9 ratio. Setting the new width to 1280 pixels produces a proportional height of 720 pixels. The original frame contains 2,073,600 pixels, or about 2.07 megapixels.

Accuracy and assumptions

  • Original and resized dimensions are whole pixels.
  • The full frame is preserved without cropping.
  • The calculated dimension is rounded to the nearest pixel.
  • Display aspect ratio and pixel aspect ratio are assumed to match.
  • File size, bitrate, codec, frame rate, and quality are not estimated.

Frequently asked questions

What does 16:9 mean?

For every 16 units of width, the frame has 9 units of height. Many different resolutions share that same proportion.

Why can the resized ratio differ slightly?

A proportional result can be fractional. Rounding to a whole pixel may create a tiny difference, especially at small dimensions.

Does this crop the image or video?

No. It calculates proportional dimensions. Cropping to a different ratio requires choosing which part of the frame to remove.

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Sources and review

The tool uses proportional scaling and greatest-common-divisor reduction. Calculator logic and examples were reviewed by the DIY Cost Tools editorial team on September 28, 2026.