Nisab is a term that denotes the minimum amount of wealth Muslims must have before Zakat becomes obligatory upon them. They are required to donate 2.5% of their total wealth to those in need.
Nisab was set by Prophet Muhammad (Ψ΅ΩΫ Ψ§ΩΩΫ ΨΉΩΫΫ ΩΨ³ΩΩ ) at 20 Mithqaal of gold or 200 dirhams of silver. This is the equivalent of 87.48 grams (7.5 tola) of gold and 612.36 grams (52.5 tola) of silver, respectively.
Important Note: If someone possesses only gold, then the Nisab level for gold (87.48 grams) must be used. However, if a mixture of assets are possessed then the (lower) silver Nisab level must be used.