For the best reach from bed, aim for your nightstand to sit between 5 and 10...
https://www.oscarbookmarks.win/aim-for-your-bedside-table-to-sit-5-to-10-cm-below-the-top-of-your-mattress
For the best reach from bed, aim for your nightstand to sit between 5 and 10 centimetres below the top of your mattress