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

How is Tether Market Cap calculated?

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

Tether Market Capitalization in USD = Number of USDT in supply X Price of one Tether in USD

Since the price of Tether 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 Tether or predict the price of Tether.