How to Calculate Nisab and Hawl for Crypto?

Short answer: What counts is the market value on the day your hawl completes; mid-year fluctuations are irrelevant. The nisab is the value of 87.48 g of gold or 612.36 g of silver — using the lower (usually silver) is the safer course that benefits the poor. The hawl is a lunar year. Details: The hawl starts the day your monetary wealth (cash + crypto + trade goods combined) first reaches nisab. Swapping coins (BTC→ETH) does not break the hawl, since all of it remains money-type wealth — just as exchanging taka for dollars does not restart the year. Evidence: Sahih al-Bukhari 1405 and Sahih Muslim 979 (no zakat below five uqiyyah — the silver nisab); Sahih al-Bukhari 1454 (Abu Bakr's letter); Ibn Majah 1792, sahih per al-Albani (the hawl condition); Quran 9:36 and 2:189 (lunar reckoning). Application: Fix one hijri date (e.g. 1 Ramadan) as your zakat day; every year on that day, value all holdings at that day's market price and pay 2.5%. For complex individual cases, consult a qualified scholar.