I live in America. What is the Zakat nisab in US dollars?

The nisab is the minimum threshold for zakat to become obligatory. Zakat on money is obligatory on gold, silver, and what takes their place, such as banknotes. The nisab for gold is 85 grams, and for silver, it is 595 grams. Given the disparity between them, and out of caution for the poor, zakat should be paid on banknotes if their value reaches the nisab of silver after a full lunar year has passed, at a rate of 2.5% of the money.