The Calculator Helper

Aspect Ratio Calculator

Resize dimensions while keeping the aspect ratio, and simplify it.

W
H
New height
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Aspect ratio
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Decimal (W ÷ H)
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New dimensions
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Megapixels
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Resized values may not be whole numbers — round to the nearest pixel where needed.

Keeping proportions intact

The aspect ratio is the relationship between width and height. To resize without stretching or squashing, both must change by the same factor — fix one new dimension and the other follows.

new height = new width × original height ÷ original width

Reducing the original dimensions to their simplest whole-number form names the ratio — 16 : 9, 4 : 3, 1 : 1 — which is handy for matching screens, social formats and print sizes.

Worked example

A 1920 × 1080 source is a 16 : 9 ratio. Resizing to a width of 1280 keeps that ratio, giving a height of 720 — the familiar 720p frame.

Where it matters

Get the ratio wrong and images stretch, videos get letterboxed, or designs crop awkwardly. Locking the aspect ratio when resizing keeps everything looking right, whether you are exporting a thumbnail or fitting artwork to a frame.

Common ratios

  • 16 : 9 — widescreen video, most monitors and TVs.
  • 4 : 3 — older screens, some cameras and projectors.
  • 1 : 1 and 3 : 2 — square social posts and classic photography.

Frequently asked questions

How is the missing dimension found?
By keeping the ratio constant. New height equals new width times original height divided by original width; swap the terms to solve for width instead.
What does the simplified ratio mean?
Dividing both dimensions by their greatest common divisor gives the smallest whole-number form — 1920 × 1080 reduces to 16 : 9, the standard widescreen ratio.
Why do my resized numbers have decimals?
Not every target size lands on whole pixels. Round to the nearest whole number; a fraction of a pixel cannot be displayed, and the visual difference is imperceptible.
What are common ratios?
16 : 9 for most video and screens, 4 : 3 for older displays, 1 : 1 for square social posts, and 3 : 2 for many photographs.