Nisab is the minimum amount that a Muslim must have before being obliged to Zakat.

The Nisab was set by Prophet Muhammad^(sa) at a rate equivalent to: 87 grams of gold and 620 grams of silver. Any value above this becomes payable at 2.5% as Zakat

As we no longer use silver or gold as currency, you need to find out the equivalent monetary exchange value of the rates the Prophet Muhammad^(sa) set in your local currency. You can do this by checking the market rate of gold and silver.

The two values used to calculate the Nisab threshold are gold and silver.