What is the price of gold considered for calculating the Zakat Nisab: is it the wholesale price, the retail price, or the global price? And to what extent is it valid to use the mentioned website for calculating the gold Nisab?

One must pay a quarter of a tenth (2.5%) of what one owns if their wealth reaches the nisab, and the amount to be paid does not change with the fluctuation of gold prices. However, if the wealth does not reach the nisab, then the market value of gold is considered, and the price most beneficial to the poor is chosen, which is usually the wholesale price. In fact, it should be valued by silver if that is more beneficial to the poor. The amount of the nisab for zakat on paper currency is what is equivalent to the value of twenty mithqals of gold or one hundred and forty mithqals of silver, choosing what is more beneficial to the poor.