Android percent screen width in RecyclerView item

You can override one of the LayoutManager methods used by your RecyclerView to force specific size:

recyclerView.setLayoutManager(new LinearLayoutManager(this){
    @Override
    public boolean checkLayoutParams(RecyclerView.LayoutParams lp) {
        // force height of viewHolder here, this will override layout_height from xml
        lp.height = getHeight() / 3;
        return true;
    }
});

This is assuming your RecyclerView fits the screen.

If you want more complex solution (custom layout manager with per-item control & percent inflation straight from from XML) see this answer.