Is Zakat obligatory on a fluctuating sum of money between 97,000 and 127,000, which is allocated for household expenses and not for trade? And if it is obligatory, how is the amount due for Zakat calculated?

Zakat is obligatory on saved money if a year has passed over it and it has reached the nisab. The nisab for currency is the equivalent of 85 grams of gold, or 595 grams of silver, and the amount of zakat is a quarter of a tenth (2.5%).