1- Nisab of gold is twenty Dinars or 85grams.
A dinar of gold equals four grams and a quarter, the Nisab of gold in grams will then be 4.25 x 20= 85grams of pure gold.
2- The Nisab of silver is two hundred dirham or 595 grams.
A dirham of silver equals 2.975 grams, the Nisab of silver in grams will then be 2.975 x 200 = 595 grams of pure silver.
3- The Nisab of paper currency is calculated on the basis of the Nisab of gold or silver when the collection of Zakah is due. When the money has reached the Nisab of either gold or silver,
Zakat then becomes obligatory.
For example, if a gram of gold equals $30, Zakah becomes obligatory if one has 30 x 85 = 2 550.
Source:
Islamkingdom