How are mutual funds in NAV calculated on the holiday?

A fund’s Net Asset Value (NAV) is the value closing on the last business day. So on a holiday the NAV will be the same as the previous business day’s closing NAV.

Just to remind that a Direct Plan NAV will not include the broker commissions. Whereas a Regular Plan NAV of the same fund will incur commissions. The daily NAV will reflect these charges, meaning that a direct plan equity fund will grow more by about 1.5%.