The formula for image ratio recalculation
The formula for image ratio recalculation
Image ratio
First image height (H1)
First image width (W1)
Second image height (H2)
Second image height (W2)
Percentage change (A)

Who has never tried to resize a photo to get a good quality on a different device, raise their hand! With this image ratio calculator, it all becomes so easy - all you need to do is insert a bit of data and the tool does the rest.

If you've ever wondered what's the difference between 1920x1080 aspect ratio and 16:9 aspect ratio, take a look at the article below. It explains the basics of this image size converter, what is aspect ratio, and, finally, the practical uses of this image ratio calculator and its aspect ratio formula.

What is aspect ratio?

In any digital medium, be it TV, photos, images, gifs, or even cinema, the aspect ratio is the precise proportion of height to width. Its purpose is to help easily resize the image so that, e.g., a photo from your iPhone looks just as good on your computer or TV screen.

1920x1080 aspect ratio and 16:9 aspect ratio differences

What are the most common aspect ratios, and how come some numbers are as small as 4:3, and the others reach 2048:1536? Let me surprise you - the resolution is the same!

The latter numbers are the dimensions given in pixels - smallest controllable element of a picture represented on a screen, while the former are simplified proportions. In the above case, if we divide both numbers, 2048 and 1536, by 512, we get:

2048/1536 = 4/3

The resolution calculator (image ration calculator)

Finding the correct ratio and proportions when you only have part of the data requires many calculations. Our image ratio calculator makes it easy!

All you need to know is three out of five variables:

  1. Height of the initial image (H1)
  2. Width of the initial image (W1)
  3. Height of the final image (H2)
  4. Width of the final image (W2)
  5. A percentage - the proportion of the initial image's ratio to the final image's ratio. (A)

The aspect ratio formulas that connect the above quantities for the ratio converter are:

H1/W1 = H2/W2,

H1 * A% = H2, and

W1 * A% = W2

You don't need to know the details by heart; if the initial resolution is commonly used, use the list to choose the appropriate ratio:

  1. Proportions
  • 4:3, the traditional television & computer monitor standard;
  • 3:2, the classic 35 mm still photographic film;
  • 16:9, the HD video standard;
  • 16:10, common for computer screens;
  • 1:1, square, in some social networks, and in few devices; and
  • 1.85:1, the cinema aspect ratio
  1. Pixels
  • 2048:1536, iPad with Retina screen;
  • 1920:1080, HD TV, iPhone 6 plus; and
  • 800:600, traditional television & computer monitor standard.

Image size converter in practice

As said above, we're moving on to practical examples. Imagine Adrien has a great photo on his iPhone (the only one from his trip that is blink-free!) in a standard resolution of 1920x1080 - given in pixels. He'd like to display the image on his computer screen, which has a 16:10 aspect ratio.

Adrien wants to know what width to choose so the photo matches the screen's height precisely. To estimate that, he uses this image ratio calculator:

  • H1 - 1920
  • W1 - 1080
  • H2 - 16
  • W2 - ?

Our aspect ratio calculator for images uses the following ratio converter formulas:

H1/W1 = H2/W2

W2 = H2 * W1/H1

W2 = 16 * 1080/1920

W2 = 9

To stay in the correct resolution, Adrien ought to choose the 16:9 aspect ratio for his image. It means that it will be slightly more narrow on the computer than the actual computer screen.

Dominika Miszewska, PhD candidate