Convert 10M rows of Text with letters To Number

Question

I need to convert "text numbers" into numbers. The text numbers look like: 32,23B or 242,23M.

I need to remove the letter and multiply by 1,000 ; 1,000,000 ; etc., depending on the letter.
The code below works, but as I need to convert 10M lines it takes ages.

Is there any clever way to do it?

For shIndex = startSheet To lastSheet
    LastRowF = Sheets(shIndex).Range("F" & Rows.Count).End(xlUp).Row
        
    For i = 3 To LastRowF
        
        Mul = Right(Sheets(shIndex).Range("F" & i), 1)
            
        Select Case Mul
            Case "K"
                Multiplier = 1
            Case "M"
                Multiplier = 1000
            Case "B"
                Multiplier = 1000000
            Case "T"
                Multiplier = 1000000000
            Case Else
                Multiplier = False
        End Select
            
        If Multiplier Then
            With Sheets(shIndex)
                .Range("F" & i) = CSng(Left(Sheets(shIndex).Range("F" & i), Len(Sheets(shIndex).Range("F" & i)) - 1) * Multiplier)
                .Range("F" & i).NumberFormat = "#,##0"
            End With
        End If
    Next i
Next shIndex

Answer 1

Use a Variant array, do the conversion in memory, then write the entire array back to the sheet:

For shIndex = startSheet To lastSheet
    LastRowF = Sheets(shIndex).Range("F" & Rows.Count).End(xlUp).Row

    Dim data() As Variant
    data = Sheets(shIndex).Range("F3:F" & LastRowF).Value

    Dim i As Long
    For i = LBound(data, 1) to UBound(data, 1)
        Mul = Right(data(i, 1), 1)

        Select Case Mul
            Case "K"
                Multiplier = 1
            Case "M"
                Multiplier = 1000
            Case "B"
                Multiplier = 1000000
            Case "T"
                Multiplier = 1000000000
            Case Else
                Multiplier = False
        End Select

        If CBool(Multiplier) Then
            data(i, 1) = Left(data(i,1), Len(data(i, 1)) - 1) * Multiplier
        End 

        With Sheets(shIndex).Range("F3:F" & LastRowF)
           .Value = data
           .NumberFormat = "#,##0"
        End With 
     
    Next
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