Round time to nearest 15 minutes

MROUND rounds to nearest values based on a supplied multiple. When you supply "0:15" as the multiple, Excel internal converts 0:15 into 0.0104166666666667, which is the decimal value that represents 15 minutes, and rounds using that value.

You can also express 15 minutes in a formula with this formula:

=15/(60*24)

The formula above divides 15 by 1440, which is the number of minutes in one day. So, to Excel, these formulas are identical:

=MROUND(B6,"0:15")
=MROUND(B6,15/(60*24))

Round to other time intervals

As you would expect, you can use the same formula to round to different time intervals. To round to the nearest 30 minutes, or nearest 1 hour, use these formulas

=MROUND(time,"0:30") //nearest 30 minutes
=MROUND(time,"1:00") //nearest 1 hour

Always round up

To always round up to the nearest 15 minutes, you can use the CEILING function:

=CEILING(B6,"0:15")

Like MROUND, the CEILING function rounds to a nearest multiple. The difference is that CEILING always rounds up. The FLOOR function can be used to always round down