For a market cap website, see CoinMarketCap
The market cap of a cryptocurrency is the total coins in circulation times the current price. Market cap is a rough value because many private keys have been lost and those coins are gone forever.
Fully Diluted Valuation
The fully diluted valuation (FDV) is the maximum supply of coins that will ever exist multiplied by the current price. The FDV is generally larger than the market cap because it can include tokens that may be locked due to vesting.
Circulating Supply vs. Total Supply
Circulating supply is the total number of coins ever mined, while total supply does not include coins that have been removed (see crypto burning
Maximum supply is the total number of coins that can ever come into existence. For example, Bitcoin will eventually be capped at 21 million coins. See Bitcoin
and crypto glossary