The average height of a dining table is between 28 and 32 inches (71 to 81 cm). You'll find that this is the most common height for dining tables sold today. This height should fit most people and is a good solution for a formal meal. Bar-height dining tables are the tallest type of table in existence, often measuring 40 to 43 inches tall.
As a matter of interest, 78.5 cm for the height of the table is actually a more authentic error, from the point of view of the time, since most of the first tables were quite tall. Due to the design of the previous table, the overall look of the time would have been compromised by making the carved table bar too short in height. With extendable tables, you have the possibility of expanding the extendable table with one or two additional removable shelves (50 cm), for 2 or 4 seats. To calculate the size of the dining table, it can also be useful to place the table and tablecloth in the room to get an idea of the size.
Once the next two points have been clarified, it will be much easier to find a suitable table and choose between the available table sizes.