What does nisab mean? What is the amount of nisab, how a persone calculate his Zakah ?
Zakat is obligatory charity.
Nisab means the minimum amount of wealth, such that if a person owns less than that then Zakat is not obligatory on them.
The Nisab for
عليك شىء - يعني في الذهب - حتى يكون لك عشرون دينارا فاذا كان لك عشرون دينارا وحال عليها الحول ففيها نصف دينار
Nothing is incumbent on you, that is, on gold, till it reaches twenty dinars. When you possess twenty dinars and one year passes on them, half a dinar is payable.
— Abu Daud
فاذا كانت لك مايتا درهم وحال عليها الحول ففيها خمسة دراهم
When you possess two hundred dirhams and one year passes on them, five dirhams are payable.
— Abu Daud
Cash, cash equivalents and Goods for sale is the valuation equal to either of the above which one feels is better. In present times some recommend using the valuation using silver since that will have more people helping others, while others prefer the valuation using gold since less poor people will be burdened with paying it.
There are different thresholds for cattle and produce from agricultural land. Items of use are not subject to Zakat.
Zakat is calculated by taking 2.5% of your net wealth that has remained in your possession for a whole lunar year.
1 There is a view that this is 87.5 grams ; also this means the pure metal (24 Karat)
2 There is a view that this is 612.36 grams