How to calculate positions(1st,2nd,3rd...) in Excel

Depends on what you want.

sample data 100,75,50,75,50,46,75,1,45,0
Sample data is in range A1:A10

If desired result should be like 1,2,5,2,5,7,2,9,8,10
So if three students got 2nd postion and two got third, and you want to say that those who are in third postion are actually at 5 position (1 for 1st, 3 for 2nd )
=RANK(A1, A$1:A$10,FALSE)
to reverse order : =RANK(A1, A$1:A$10,TRUE)


If desired result is 1,2,5,3,6,7,4,9,8,10
So it does not skip any number and rank the same number in sequence, So first person at 2nd postion is given rank 2, and 2nd person at postion 2, is given rank 3
=RANK(A1, A$1:A$10,FALSE)+COUNTIF(A$1:A1,A1)-1
to reverse order =RANK(A1, A$1:A$10,TRUE)+COUNTIF(A$1:A1,A1)-1

If desired result is 1,2,3,2,3,4,2,6,5,7
So if values are same, the rank is same and next ranking is to be sequencial, then you have to use an array formula. To enter array formula, type in the formula and press control, shift and enter key at the same time
=SUMPRODUCT(1 * (COUNTIF(OFFSET(A$1,,,ROW(A$1:A$10)-ROW(A$1)+1),A$1:A$10)=1) * (A$1:A$10>=A1))
to reverse order: =SUMPRODUCT(1 * (COUNTIF(OFFSET(A$1,,,ROW(A$1:A$10)-ROW(A$1)+1),A$1:A$10)=1) * (A$1:A$10<=A1))