Worksheets("Sheet1").Columns("O").Rows.AutoFit

Sub AutofitRowsToColumnO()
    Dim ws As Worksheet
    Dim rng As Range
    Dim cell As Range
    Dim minHeight As Double
    
    Set ws = ActiveSheet
    ' Work on used range in Column O
    Set rng = ws.Range("O1:O" & ws.Cells(ws.Rows.Count, "O").End(xlUp).Row)
    
    Application.ScreenUpdating = False
    
    For Each cell In rng
        ' Autofit just this cell
        cell.EntireRow.AutoFit
        
        ' Now capture its required height
        minHeight = cell.RowHeight
        
        ' Reset row height to this minimum
        cell.EntireRow.RowHeight = minHeight
    Next cell
    
    Application.ScreenUpdating = True
End Sub