Work out the Zakat due on the savings you've built up from your salary, once they cross the Nisab threshold, using today's gold or silver rate.
Zakat isn't charged on your salary the moment it's paid. It applies to what you've kept as savings once that amount has sat at or above the Nisab threshold continuously for a full lunar (Hijri) year. Because gold and silver rates move daily, enter today's rate per gram for an accurate Nisab figure rather than relying on a fixed number.
Add up your cash savings, gold and other zakatable assets, then subtract any short-term debts to get your total zakatable wealth. Pick a Nisab standard and enter today's rate per gram, and the tool compares your wealth against that threshold. If you're at or above it, it works out 2.5% of your total wealth as the Zakat due.
The two classical thresholds are 87.48 grams of gold or 612.36 grams of silver. Since silver is worth much less per gram, the silver-based Nisab is a lower bar. Many scholars recommend using it, since it means more people who can afford to give Zakat actually do, benefiting more of those in need.
On savings, the portion of salary you've kept for a full lunar year at or above the Nisab threshold, not on salary as it's earned.
The minimum wealth threshold for Zakat to apply, 87.48g of gold or 612.36g of silver. The silver standard is lower and more commonly recommended.
2.5% (1/40th) of zakatable wealth held for a full lunar year above the Nisab.