For a comfortable reach, your nightstand should sit level with the top of your...

https://fionafreshmaids.com/the-ultimate-guide-choosing-the-perfect-bedside-table-height-for-a-65-cm-mattress/

For a comfortable reach, your nightstand should sit level with the top of your mattress or just 5–10 cm below it. Most UK beds work best with a table height between 55 and 70 cm. Measure from your floor to the top of your mattress before you buy