Market capitalisation is the number every ranking site leads with, and it is one of the most misread figures in the crypto market. It is simple to calculate and easy to mistake for a measure of safety, depth, or how much money is actually in a coin. It is none of those things on its own. Reading it correctly means knowing exactly what it does and does not say.
What market cap actually measures
Market cap is just price multiplied by the circulating supply of a coin. If a coin trades at one dollar and ten million units are in circulation, its market cap is ten million dollars. That is the whole calculation. It gives you a rough sense of the relative size of one market against another, and little more without further context.
What it does not tell you
The figure does not mean that much money could leave the coin at today's price. Price is set at the margin, by the last trades on the order book — not across every unit at once. A large market cap can sit on top of a thin book, where selling even a modest amount walks the price down through the bids. In other words, market cap says nothing direct about liquidity, and liquidity is what governs your real cost to enter and exit.
The supply trap
Two coins with the same market cap can have wildly different supplies. One might have a few million units priced high; another, billions priced in fractions of a cent. A low unit price is not "cheap" and a high one is not "expensive" — those words only make sense relative to supply and to what the asset does. Confusing a low per-unit price for value is a common beginner error worth naming plainly.
How a disciplined trader uses it
Treat market cap as a coarse size filter, not a verdict. A larger-cap pair is usually, though not always, deeper and tighter to trade than a micro-cap one, which matters for your fills. But the figure never replaces looking at the actual spread, the depth of the book, and how the pair behaves under stress. Size is context; it is not safety.
To see how the three largest crypto markets differ in purpose and behaviour, read Bitcoin, Ethereum, and Litecoin compared. And for the rest of the vocabulary that surrounds this one, see the crypto trading terms glossary. Nothing here is a recommendation to buy any coin — it is context so a headline number does not mislead you.