Depending on your bracket for 2017, that could range from a tax rate of 10% to 39.6%

If you sold or used any Bitcoin after owning it for more than a year, they are considered long-term gains with a taxable range from 0% to 20% depending on your household income.

I found this on Investopedia - "In the US, long-term capital gains tax rates are 0% for people in 10%-15% ordinary income tax rate bracket, 15% for people in the 25%-35% tax bracket, and 20% for those in the 39.6% tax bracket."