Add common prefix to all cells in Excel

Select the cell you want,

Go To Format Cells (or CTRL+1),

Select the "custom" Tab, enter your required format like : "X"#

use a space if needed.

for example, I needed to insert the word "Hours" beside my numbers and used this format : # "hours"

Select the cell you want to be like this, go to cell properties (or CTRL 1) under Number tab in custom enter "X"@

Put a space between " and @ if needed

Select the cell you want to be like this, Go To Cell Properties (or CTRL 1) under Number tab in custom enter "X"#

Type this in cell B1, and copy down...

="X"&A1

This would also work:

=CONCATENATE("X",A1)

And here's one of many ways to do this in VBA (Disclaimer: I don't code in VBA very often!):

Sub AddX()
    Dim i As Long

    With ActiveSheet
    For i = 1 To .Range("A65536").End(xlUp).Row Step 1
        .Cells(i, 2).Value = "X" & Trim(Str(.Cells(i, 1).Value))
    Next i
    End With
End Sub