What is Fully diluted valuation (FDV)?
The market cap a coin would have if every token that will ever exist were already in circulation, at today's price.
FDV multiplies the current price by the maximum supply (or the total supply when there is no maximum). It shows how much future issuance is still waiting.
When FDV is far above market cap, a large share of tokens is still locked or not yet minted. As those tokens are released through token unlocks or emissions, they add selling pressure unless demand grows to match. A coin with a $100 million market cap and a $2 billion FDV has twenty times more supply to come.
FDV is not a forecast: it assumes the price stays the same while supply grows, which rarely happens. Treat it as a measure of dilution risk.