Case Insensitive Id Converter for Salesforce
Convert 15-character to 18-character ids in Excel for uniqueness

Courtesy of Johan Yu of simplysfdc.com

This is one of those situations where google results and help threads have led me astray so I put this here.

This one works and you should just copy and paste it (with the id in Column A)

CREDIT:

Johan Yu
@simplysfdc

https://www.simplysfdc.com/2018/03/salesforce-convert-id-from-15-to-18.html


=CONCATENATE(A2,
MID("ABCDEFGHIJKLMNOPQRSTUVWXYZ012345",(
IFERROR(IF(FIND(MID(A2,1,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,1,0),0)
+IFERROR(IF(FIND(MID(A2,2,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,2,0),0)
+IFERROR(IF(FIND(MID(A2,3,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,4,0),0)
+IFERROR(IF(FIND(MID(A2,4,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,8,0),0)
+IFERROR(IF(FIND(MID(A2,5,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,16,0),0)
+1),1),
MID("ABCDEFGHIJKLMNOPQRSTUVWXYZ012345",(
IFERROR(IF(FIND(MID(A2,6,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,1,0),0)
+IFERROR(IF(FIND(MID(A2,7,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,2,0),0)
+IFERROR(IF(FIND(MID(A2,8,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,4,0),0)
+IFERROR(IF(FIND(MID(A2,9,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,8,0),0)
+IFERROR(IF(FIND(MID(A2,10,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,16,0),0)
+1),1),
MID("ABCDEFGHIJKLMNOPQRSTUVWXYZ012345",(
IFERROR(IF(FIND(MID(A2,11,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,1,0),0)
+IFERROR(IF(FIND(MID(A2,12,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,2,0),0)
+IFERROR(IF(FIND(MID(A2,13,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,4,0),0)
+IFERROR(IF(FIND(MID(A2,14,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,8,0),0)
+IFERROR(IF(FIND(MID(A2,15,1),"ABCDEFGHIJKLMNOPQRSTUVWXYZ")>0,16,0),0)
+1),1))