How can you say that 12-14 sq meter per ton if you have any proof in the cal?

Dear friend

The value seems too high. for office and residential application it may reach to 17 - 20 sq meter per ton. Any how these values all come from calculations when we have total tonnage and total cooling area and we divide are by ton it comes with values like these so every body uses these values as rule of thumb and quick checking of total load

These values were taken after a lot of calculations done be expert people in almost fixed wither data limits this called the rule of thumb. If you search for it, you may found great books about it, which means it wasn't by luck, it is a great effort to collect this data, we have to respect it, but don't follow it.

this rule of thumb should be different from country to another according to the difference of weather data, human culture, and their knowledge about using AC.