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Aspect Ratio Calculator

Calculate a new image or video width and height while keeping the original aspect ratio.

Runs in your browserFree · No account required

Resize dimensions without changing aspect ratio

Enter the current pixel width and height, then set either a new width or height. The other dimension is rounded to the nearest whole pixel. The calculator does not resize or edit an image file.

1

Enter your details

Change the values, then run the tool.

Data handling

Processing
The selected input is processed in your browser. Got A Tool does not send it to our servers.
Retention
We do not retain selected files. Resetting or closing this page clears its working state.
Export
The tool may prepare a result after you run it. It downloads or copies it only when you choose that action.

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How it works

Aspect Ratio Calculator: a practical guide

An aspect ratio describes the proportional relationship between an image's width and height. When one dimension changes, the other can be calculated from the original ratio. This calculator is useful for planning image, video, slide, and thumbnail dimensions before using an editor or image converter.

  1. STEP 01

    Enter the original width and height in whole pixels.

  2. STEP 02

    Choose whether to set a new width or a new height.

  3. STEP 03

    Enter the target dimension and calculate the matching whole-pixel size.

What this tool does and its limits

The original ratio is reduced to the simplest integer pair, then the other target dimension is rounded to the nearest whole pixel. Rounding can create a difference of less than one pixel from the exact mathematical ratio. The calculator does not inspect or resize a file; use an image editor or Image Converter to make the actual change.

Processing happens in your browser. The selected file or entered values are not uploaded to Got A Tool or saved by this tool.

Frequently asked questions

Does this resize my image?
No. It calculates dimensions only. Use an image tool to resize the file itself.
Why is the calculated side rounded?
Raster image dimensions use whole pixels, so a fractional result is rounded to the nearest integer.
Which values are accepted?
Positive whole-number dimensions from 1 to 1,000,000 pixels.
What is an aspect ratio?
It is the width-to-height proportion, often written as 16:9 or 4:3. Images with the same ratio can have different pixel sizes.

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