ROUNDDOWN

ROUNDDOWN(number, [digits])

Rounds a number towards zero, such as the whole weeks of float a task has. Towards zero, not down: -7.5 becomes -7, so negative float rounds to fewer weeks behind, not more. It rounds numbers only, so a duration is turned into days or hours first with INDAYS or INHOURS.

Arguments

ArgumentWhat to give it
numberA number. A blank gives a blank.
digitsOptional, 0 when left out. The decimal places to keep; a negative count rounds to tens, hundreds and so on.

Examples

Formula
=ROUNDDOWN(INDAYS([Total float]) / 5, 0)

The whole five-day weeks of float the task has.

Measure (on the project)
=ROUNDDOWN(INDAYS(SUM(Tasks[Duration])) / COUNT(Tasks), 0)

As a measure: the average task duration in whole working days, the part day dropped.

Reach for something else when

You wantUse
To the nearest, halves away from zeroROUND
Away from zeroROUNDUP

Common questions

What does "ROUNDDOWN rounds numbers; for a duration use ROUNDDOWN(INDAYS(…))" mean?

A duration has to be counted in days or hours before it can be rounded: use INDAYS or INHOURS.

The editor refuses this
=ROUNDDOWN([Total float], 0)