The column number of a reference, or of the current cell. Drives column indexes that follow a formula copied right.

Syntax

=COLUMN([reference])

• Current column

  =COLUMN() → 3

  Typed in column C.

• Column of a reference

  =COLUMN(D1) → 4

  The column of a reference.

• Relative index

  =COLUMN()-COLUMN($B$1)+1 → 2

  In column C: a relative index that starts at 1 in column B.

• VLOOKUP that fills right: col_index_num = COLUMN()-COLUMN($A$1)+1.
• Letter of the current column: =SUBSTITUTE(ADDRESS(1,COLUMN(),4),"1","").
• COLUMNS($A$1:B$1) is a cleaner relative counter.

• Inserting columns shifts the numbers.
• Returns an array for multi-column references.