SharePoint time difference in minutes - wrong result

Question

I created a simple SharePoint list and I am having problem with a calculated field. I have a "Duration" field that calculates the minutes between the start and end date/time columns, using the formula:

=INT(([RRT End (EST)]-[RRT Start (EST)])*1440)

The odd thing is it works correctly if the difference in minutes is 62 or above, but 61 or below it returns an incorrect (-1) result. It does not seem to be tied to the dates themselves, It only happens if the difference is 61 minutes or less. See below.

Any idea how to fix without using a workaround IF formula?

Answer 1

With INT() you're cutting off decimals that contribute to the correct minute value.

Try rounding to zero decimals instead, like =ROUND((end-start)*1440,0)