The golden rule for bedside tables is comfort and accessibility. Aim for a...

https://www.nav-bookmarks.win/for-the-most-practical-setup-aim-for-your-nightstand-to-sit-between-5-and-10

The golden rule for bedside tables is comfort and accessibility. Aim for a height that sits 5 to 10 cm below the top of your mattress. This prevents you from knocking things over or having to reach up awkwardly while in bed