Calculate a Count with a Weight

Hi All,

I am trying to get a count of how many unique IDs are in a column and then I want to factor in a weight associated with each row... this will change the count slightly. let's say I have 5 rows; however, each row is weighted at .5... any suggestions on how to get the calculation to total 2  in Power BI?

for instance, see below

row1                    weight

1                              .5

2

3

4

5