To get the perfect bedside table height, aim for the top surface to sit roughly...

https://www.fastbookmarks.win/ideally-your-bedside-table-should-sit-5-10-cm-below-the-top-of-your-mattress

To get the perfect bedside table height, aim for the top surface to sit roughly 5 to 10 centimetres below the top of your mattress. Most standard UK beds work well with tables in the 55 to 70 centimetre range