There are a few "density buckets" in android, they are: LDPI, MDPI, HDPI, XHDPI, XXHDPI and XXXHDPI.
PPI and DPI are basically the same for these calculations, they mean pixels or dots per inch.
Use these steps to get the best results:
- Resize the image to be the smallest possible size that still looks good on the device you're testing on.
- Find out the DPI of the device you are testing on by googling "
device model PPI", for example, googling "moto g 2014 ppi" gives out 294 PPI.
- Choose the correct density bucket your device is closest to:
- LPDI – 0.75 * MDPI size (120 PPI)
- MDPI – default (160 PPI)
- TVDPI - 1.33 * MDPI size (213 PPI)
- HDPI – 1.5 * MDPI size (240 PPI)
- XHDPI – 2 * MDPI size (320 PPI)
- XXHDPI – 3 * MDPI size (480 PPI)
- the jump from XHDPI to XXHDPI is 1.5 = 480/320
- the jump from XXHDPI to XXXHDPI is 1.33 = 640/480