Welcome.
Use:
Code:=MATCH(valuetolookup,A1:A25,TYPE)
About Match TYPE:
use 0 type for exact
use 1 for largest value that is less than or equal to the value
use -1 to match the smallest value that is less than or equal to the value defined.
An example formula is:
Code:=MATCH(10,A1:A25,0)
That will search A1 through A25 for the exact value of 10.