Option Explicit

Private sinFTime(1 To 2) As Single, sinETime(1 To 2) As Single
Private Sh As Worksheet

Sub Speed_Test_Calculation2()
    Dim i As Long, ii As Long
    With Application
        .ScreenUpdating = False
        Set Sh = .Worksheets(2)
        With Sh
            .Cells.ClearContents
            .Range("B1").Formula = "=A1"
            For i = 18 To 27
                Call Test1
                Call Test2
                For ii = 1 To 2
                    Worksheets(1).Cells(i, ii + 1).Value = sinETime(ii)
                Next
            Next
        End With
        .ScreenUpdating = True
    End With
End Sub

Private Sub Test1()
    Dim i As Long, c As Long
    sinFTime(1) = Timer
    For i = 1 To 1000
        c = i
    Next
    sinETime(1) = Timer - sinFTime(1)
End Sub

Private Sub Test2()
    Dim i As Long, c As Long
    sinFTime(2) = Timer
    For i = 1 To 1000
        Application.Calculation = xlCalculationManual
        c = i
        Application.Calculation = xlCalculationAutomatic
    Next
    sinETime(2) = Timer - sinFTime(2)
End Sub