Hope this helps: Getting Your Apps Ready for Nexus 6 and Nexus 9
Nexus 6
Screen
The Nexus 6 boasts an impressive 5.96” Quad HD screen display at a
resolution of 2560 x 1440 (493 ppi). This translates to ~ 730 x 410 dp
(density independent pixels).
Check your assets
It has a quantized density of 560 dpi, which falls in between the
xxhdpi and xxxhdpi primary density buckets. For the Nexus 6, the
platform will scale down xxxhdpi assets, but if those aren’t
available, then it will scale up xxhdpi assets.
EDIT:
Consider this line
2560 x 1440 (493 ppi). This translates to ~ 730 x 410 dp (density
independent pixels)
It implies the scaling factor is 2560/730 = 1440/410 ~ 3.5
For a screen of width 410 and height 730 in dp, if you want to specify a button of half the screen width in dp, the width should be 410/2 = 205 dp which translates to 717px = 205*3.5 (width in dp * scaling factor)
A button of size 100px x 50px would translate to 28 x14 dp (100/3.5 * 50/3.5) on a 410 x 730 dp screen size.