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

How is Ethereum Market Cap calculated?

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

Ethereum Market Capitalization in USD = Number of ETH in supply X Price of one Ethereum in USD

Since the price of Ethereum 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 Ethereum or predict the price of Ethereum.