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Aspect Ratio Calculator

Find the aspect ratio of any size, or the missing width or height to resize an image or video to a ratio.

Your size

Filled in with example values. Replace them with your own.

Pixels, or any other unit: the ratio is the same.

Results update as you type.

Result

1920 × 1080 = 16:9 (1.78:1)

Aspect ratio

16:9

1,920 × 1,080, 1.78:1.
As a decimalWidth ÷ height
1.78:1
Common nameWithin 1%
16:9
Orientation
Landscape

How it’s calculated

  1. Greatest common divisor

    of 1920 and 1080 = 120

  2. Ratio

    1920 ÷ 120 : 1080 ÷ 120 = 16:9

How the aspect ratio calculator works

An aspect ratio describes the shape of a rectangle: its width compared with its height. To find it, the calculator divides the width and height by their greatest common divisor. To resize, it keeps that ratio and works out the missing side.

The formula

Ratio = Width ÷ GCD : Height ÷ GCD

New height = New width × Ratio height ÷ Ratio width

New width = New height × Ratio width ÷ Ratio height

GCD is the greatest common divisor, the largest number that divides both sides exactly.

Worked examples

  • 1920 × 1080: the GCD is 120, so the ratio is 1920 ÷ 120 : 1080 ÷ 120 = 16:9.
  • 16:9 at 1280 wide: 1280 × 9 ÷ 16 = 720 high.
  • 21:9 at 1080 high: 1080 × 21 ÷ 9 = 2520 wide.

Frequently asked questions

What does 16:9 mean?

For every 16 units of width there are 9 units of height. A 1920 × 1080 screen and a 1280 × 720 video are both 16:9, because dividing both sides by the same number gives 16 and 9.

Why is my resolution not a round ratio?

Some resolutions are only close to a common ratio. 1366 × 768 reduces exactly to 683:384, which is within 0.05% of 16:9. The calculator shows the exact ratio and names a common one when it is within 1%.

Why is the result rounded?

Pixels come in whole numbers, so the missing side is rounded to the nearest pixel. The exact value is shown when it is not whole, so you can choose a size that divides evenly if you need one.

Can I use a decimal ratio such as 2.35:1?

Yes. Enter 2.35 and 1; the calculator works with the ratio exactly and shows it in whole numbers as well (47:20).

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