How is the Zakat calculated for a sum of 250,000 EGP saved while building a house, after spending 500,000 EGP on purchasing the land and construction?

The savings you have accumulated from your salaries are subject to zakat upon the completion of a full lunar year (hawl) from the day you first possessed the minimum threshold (nisab). Any new salaries acquired should be added to this amount. The jurist (faqih) has the option to either combine the new salaries with the initial wealth and pay zakat on the total sum, or to assign a separate hawl for each new salary. The easier method and the more beneficial one for the poor is to pay zakat on all savings upon the hawl of the first nisab. If the savings are spent on building a residence and no nisab remains, then no zakat is due. The nisab is equivalent to 85 grams of gold or 595 grams of silver, and the zakat amount is one-quarter of one-tenth (2.5%).