And just in case you try to add too many rows:-
Sub InsertBlankRows()
Application.ScreenUpdating = False
Dim numRows As Long
Dim r As Long
Dim Rng As Range
Dim lastrw As Long
Dim n As Long
Dim rrc As Long
Dim rc As Long
Dim mn As Long
numRows = InputBox("How many Rows")
On Error Resume Next
lastrw = Cells(Rows.Count, "A").End(xlUp).Row
Set Rng = Range(Cells(1, "A"), Cells(lastrw, "A"))
rrc = Rng.Rows.Count
rc = Rows.Count
n = rrc * numRows
mn = Int(rc / rrc)
If n > rc Or rrc > rc / 2 Then GoTo ErrorMsg
For r = Rng.Rows.Count To 1 Step -1
Rng.Rows(r + 1).Resize(numRows).EntireRow.Insert
Next r
Application.ScreenUpdating = True
Exit Sub
ErrorMsg: MsgBox ("- The max number of rows you can run this with is 32,767" _
& vbCrLf & "- Your range contains " & rrc & " rows" _
& vbCrLf & "- The Max number of blank rows you can insert" _
& " on this range is " & mn - 1 & " rows per line of data" _
& vbCrLf & "- Try again with fewer rows")
InsertBlankRows
End Sub