How market cap is calculated
Market capitalisation = current price × circulating supply.
If a coin is trading at $2 and there are 500 million coins in circulation, its market cap is $1 billion. Simple enough. The number is used everywhere: coin rankings, portfolio tracking tools, index construction, and media coverage.
What market cap actually tells you
Market cap is a measure of the market's current implied valuation of the entire circulating supply at the marginal price. That last phrase matters: at the marginal price.
When Bitcoin trades at $90,000, that price is set by the last trade — the marginal transaction. The market cap of $1.8 trillion doesn't mean there's $1.8 trillion of cash that has flowed into Bitcoin. It means that if you multiplied every circulating coin by today's marginal price, you'd get $1.8 trillion.
This is a subtle but important distinction. In equity markets, market cap is also a marginal-price measure, but the underlying asset (a company's earnings) has an independent, verifiable value. In crypto, the underlying asset often has no cash-flow-based value anchor. Market cap measures consensus sentiment, not fundamental value.
Three ways market cap misleads in crypto
1. Supply definitions are inconsistent
"Circulating supply" is self-reported and defined differently by different projects. Some teams hold back large amounts for foundations, treasuries, and future grants. Whether those tokens are "in circulation" varies. CoinMarketCap and CoinGecko use different methodologies, which is why the same coin can show different market caps on different platforms.
2. Illiquid supply inflates the number
Many tokens have significant portions of supply locked in smart contracts, vesting schedules, or long-term holder addresses that haven't moved in years. Those coins are technically in circulation but functionally illiquid. If those holders decided to sell, the price — and therefore the market cap — would collapse before they could exit.