The calculation is simple.
Value of your investment minus value of your final capital when you cash out equals what you have to put in your tax return.
Theory is simple, but the actual practice is not. If you buy BTC for 300, two years ago, and brought ETH from portion of it in 2017, which you invested into ICO, then you sold it to ETH. Each of those transaction is applicable to the tax calculation. Doing this for active investor in crypto ICO, coins, is quite cumbersome.
If your hidden question is : Is there a way to hide my gain.
The answer is : Yes you can try
Well I want interested in hiding my gain, but I seem to understand most of people in crypto currently are hiding the gains. I am trying to understand, is it because of lack of knowledge about tax or its truly tax free. From what i understand thus far, its definitely not tax free. So why were there only 600-800 people filing crypto on their tax return between between 2014-2016 (per IRS).
Thus, trying to find more knowledge from fellow community members, or share some knowledge thus far.