SUMIFS always takes threes arguments: =SUMIFS(range_to_sum, criteria_range, criteria)
To sum all the values equal to 5 in column A using SUMIFS, I would write:
=SUMIFS(A2:A100, A2:A100, 5)
No argument can be skipped when you use SUMIFS. The range_to_sum is the same as the criteria range but you must write it twice.
SUMIF has two forms: =SUMIF(range, criteria) and SUMIF(criteria_range, criteria, range_to_sum)
With the two-argument form, the range_to_sum must be the criteria_range.
When you use the three-argument form, the criteria_range and the range_to_sum may be different, but they may also be the same range.
To sum all the values equal to 5 in column A using SUMIF, you could write:
=SUMIF(A2:A100, 5)
Or you could write:
=SUMIF(A2:A100, 5, A2:A100)
I unintentionally misled you with 'TRUE' in my one formula. Dave's data wasn't yet posted and I simply wanted to write a generic criteria. I apologize for the confusion.