The tax rate will depend on your tax bracket that you are currently in and whether the gains will be short-term or long-term.
If you're in
the 10% or 15% tax bracket, you won't owe any capital gains taxes on
securities you've held long-term, including mutual fund shares. Long term-capital gain rates range from 0%—20% and may also be
subject to the 3.8% Medicare Surtax above a certain income threshold.
https://personal.vanguard.com/us/insights/article/cap-gains-explained-112015
http://www.investopedia.com/articles/investing/091715/basics-income-tax-mutual-funds.asp