Zakat is 2.5% (one fortieth) of your net zakatable wealth, once it has stayed at or above the nisab for a full lunar (Hijri) year.
The nisab is the minimum wealth on which zakat becomes due: the value of 52.5 tola (612.36 g) of silver or 7.5 tola (87.48 g) of gold. Many scholars recommend the silver nisab because it is lower, so more people give.
Cash, bank balances, gold and silver, shares and investments, business stock at its sale value, and money others owe you that you expect to get back.
Your home, car, furniture, clothes and the tools or machines you use for work are not zakatable. Debts and bills due now are subtracted.
Prices change every day and differ by city, so the calculator uses the rate you enter instead of a figure that could be out of date.
No, it's a calculator to help with the arithmetic. For special cases such as business partnerships or long-term debts, ask a scholar you trust.