How to retrieve the width and height exposed to the Grid?

I want to divide a grid in three equal (absolute) horizontal parts.

For instance: three parts.

My idea would be that of creating Column definitions that have an absolute width of one third of Application.Context.Resources.DisplayMetrics.WidthPixels.

So,

int DeviceWidth= Application.Context.Resources.DisplayMetrics.WidthPixels;
new ColumnDefinition {Width = new GridLength(DeviceWidth/3, GridUnitType.Absolute) }, //0
new ColumnDefinition {Width = new GridLength(DeviceWidth/3, GridUnitType.Absolute) }, //1
new ColumnDefinition {Width = new GridLength(DeviceWidth/3, GridUnitType.Absolute) }, //2

However, with a Google Nexus 4.4.2, this makes the cells HUGE.

The only way to have this working is using one SIXTH

new ColumnDefinition {Width = new GridLength(DeviceWidth/6, GridUnitType.Absolute) }, //0
new ColumnDefinition {Width = new GridLength(DeviceWidth/6, GridUnitType.Absolute) }, //1
new ColumnDefinition {Width = new GridLength(DeviceWidth/6, GridUnitType.Absolute) }, //2

I guess this means that the double density comes into play?

How to retrieve the real widths and hieghts that the device exposes to the views?