In Sharia (Islamic Law) niṣāb (نِصاب) is the amount one's net worth must exceed for the Muslim owner to be obligated to give zakat. Several hadith have formulas for calculating niṣāb, the most prominent of which declaring that No Zakāt is due on wealth until one year passes. Zakat is then determined based on the amount of wealth acquired; the greater the assets, the greater the tax. It is not subject to special exemptions. (Unlike Income Tax in secular states.)

The Quran states that Nisab is twenty for gold (dinārs) and 200 for silver (dirḥams). With today's weights, the zakāt-payable amount is 85 grams of gold or 595 g silver. In general, niṣāb is considered an amount equal to the essential needs of a person or family for one year. This year begins on the date the wealth is obtained; so long as the assets are in its owner's possession at the beginning and end of the lunar year, the zakat tax is applicable. In many modern societies, niṣāb is considered equivalent to a governmentally determined poverty threshold.