NAV is the value per share of a mutual fund, at any given day or time. It is calculated by dividing the total value of all the assets in a portfolio, minus all its liabilities.
NAV calculation is impossible during market hours as the price of the underlying holdings change every minute, so mutual funds trade only once per day, after the markets close at 4 p.m. ET.
This means that any customer will receive the close of market price on the day they purchase or sell shares of a mutual fund, and that you will therefore not necessarily know the exact NAV when you buy or sell shares.
Please note that the price you see on our site will reflect the previous day's closing price. Morningstar, Yahoo Finance, or Google Finance are also great resources for finding the previous day’s closing price.
For further reading: Morningstar NAV Explanation