You can check out above graph to see how the market cap of QTUM has changed over time. The market cap value depends on the value of QTUM on that particular day and number of QTUM in supply at that day.

How is QTUM Market Cap calculated?

The QTUM Market cap is calculated using a simple formula. You can find it below:

QTUM Market Capitalization in USD = Number of QTUM in supply X Price of one QTUM in USD

Since the price of QTUM 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 QTUM or predict the price of QTUM.