You can check out above graph to see how the market cap of Monero has changed over time.
The market cap value depends on the value of Monero on that particular day and number
of Monero in supply at that day.
How is Monero Market Cap calculated?
The Monero Market cap is calculated using a simple formula. You can find it below:
Monero Market Capitalization in USD = Number of XMR in supply X
Price of one Monero in USD
Since the price of Monero is highly volatile you can see the market cap going up and down a lot.
Sometimes price and market cap are not linear to each other due to increase in the supply of coins in the market and
stable or decrease in the price of the coin. So you can say that it's not simple to predict the market cap of Monero or
predict the price of Monero.