How much does setting these properties speed up your Excel macro: Application.ScreenUpdating, Application.DisplayAlerts

It depends on how much you are actually updating on the screen as part of your code, (i.e. number of cells updated), and how many sheets are there, how many sheets/cells refer to sheet your code is updating and how many formulas are present in the whole workbook.

Each time you change some thing in the sheet, Excel re-calculates all formulas. So if your code is not updating too many sheets/cells but your workbook has many formulas then turning off the screen update might not help you at all.

One more thing to consider for perfomance is Calculation property, set this to xlCalculationManual to turnn off the auto recals and turn it back to xlCalculationAutomatic at the end.

Application.Calculation = xlCalculationManual

One more thing to conside is Events, if one or more of those sheets have Worksheet_Chnage or Worksheet_Calculate event handlers each change that your code is doing will trigger them and your code need to wait till they return. So turn it off during your code.

Application.EnableEvents = False

In most of my code, I usually use this

On Error GoTo lblError
Dim bEvents As Boolean, iCalc As Integer, bScrnUpd As Boolean
bEvents = Application.EnableEvents
iCalc = Application.Calculation
bScrnUpd = Application.ScreenUpdating
Application.EnableEvents = False
Application.Calculation = xlCalculationManual
Application.ScreenUpdating = False

'-----------------------My code

Application.EnableEvents = bEvents
Application.Calculation = iCalc
Application.ScreenUpdating = bScrnUpd
Exit Sub

'reset them even if you are exiting due to error
lblError:
Application.EnableEvents = bEvents
Application.Calculation = iCalc
Application.ScreenUpdating = bScrnUpd
Debug.print Err.Description

The improvement of screenUpdating depends largely on how your macro is written. It will be specially usefull with those horrible macros made by the recorder, full of unnecessary "select" and "activate".

Agree.

I have found that when you turn off ScreenUpdating, Calculation, it's best to think about how to do as much work (writes,reads,events,...) as possible for as few ScreenUpdating calls in return. This will speed up operations while also providing the user with a better and more tolerable experience. Say, for example that you want to write some data to a sheet as fast as possible. You could do this:

For Each row In rowDic.Keys()
    ' turn off updating
    for item in rowDic.Key(row)
        ... do some writes
    Next             
    ' turn on updating
Next

or to go faster you could do this:

' turn off updating
For Each row In rowDic.Keys()
    for item in rowDic.Key(row)
        ... do some writes
    Next             
Next
' turn on updating

Similarly, when writing data, it's quickest to write larger chunks, fewer times. so the ideal number of writes, if any, is one. You can do this by treating a Rangeas a 2D array[rows,cols]. I have found the following to be effective:

' turn off updates

' Organise data in ram so that it fits the range for which it is meant
Dim two_d_arr (rows,cols)
loadDataFromSource two_d_arr

Dim destinationRange as Range
destinationRange = Sheets(someSheet).Range(someRange).Value = two_d_arr

Redim two_d_arr(0,0) ' !!! RELEASE MEMORY
' turn on updates

Here, there are no loops, this optimises each individual task's time in the CPU which results in quicker processing times and in turn seems to make excel work normally (not crash).

HTH,

F