Is the method of calculating gold zakat based on its total value at the time the annual zakat is paid correct? And what is the correct method if it is wrong?

If gold is jewelry prepared for permissible use, there is no zakat on it according to the majority of scholars. Otherwise, zakat is obligatory on it. The nisab (minimum threshold) for gold is 85 grams of pure gold, or its equivalent in gold of different carats. If the gold reaches this nisab, then one-quarter of one-tenth (2.5%) of it must be given as zakat, which means 2.125 grams for every 85 grams. It is permissible to give the value of the zakat in the current currency at the time of giving the zakat.