I will not give you an extended explanation here, just teach me how to calculate the image sizes for each density, which is the purpose of the question. For a general explanation of density, pixel resolution, etc. refer to the documentation .

The densities are, in order from lowest to highest: ldpi, mdpi, hdpi, xhdpi, xxhdpi and xxxhdpi.

There is a relation of proportion between them (1: 2: 3: 4: 6: 8), which means: an mdpi figure is twice the size of an ldpi (2: 1 ratio), hdpi is triple of a ldpi (3: 1 ratio), etc. Of course, ldpi has the same ldpi size, that is, a ratio of 1: 1.

But this relationship is only useful in the way it is (1: 2: 3: 4: 6: 8) if you take as base the density ldpi, which is the lowest. If you rely on another resolution, you will need to recalculate these values (the ratio between them will be maintained).

For example: taking the case of your Samsung SIII, which has xhdpi density. The ratio ratio for itself is 4: 4 = 1. So take the value 4 as a divisor (second operand of a division). The dividend (first operand) will be the density for which you want to calculate the image size. For example, if you want to calculate for hdpi, the ratio will be 3: 4 = 0.75. That is, the corresponding hdpi image will be 0.75 times (or three quarters) smaller than the xhdpi image. This means that the 150x100 pixels in xhdpi will become 112.5 x 75 pixels (or 112 x 75, as it has to be integers) on a hdpi screen.

The same logic can be applied to obtain the images in the other densities. So:

```
xxxhdpi = 300x200 px
xxhdpi = 225x150 px
mdpi = 75x50 px
ldpi = 37x25 px
```