델파이 헬프의 예제입니다..

function Sum( var X: arrayof Double): Double;

var
  I: Word;
  S: Real;
begin
  S := 0; { Note that open array index range is always zero-based. }
  for I := 0 to High(X) do S := S + X[I];
  Sum := S;
end;

procedure TForm1.Button1Click(Sender: TObject);


var
  List1: array[0..3] of Double;
  List2: array[5..17] of Double;
  X: Word;
  S, TempStr: string;
begin
  for X := Low(List1) to High(List1) do
      List1[X] := X * 3.4;
  for X := Low(List2) to High(List2) do
      List2[X] := X * 0.0123;
  Str(Sum(List1):4:2, S);
  S := 'Sum of List1: ' + S + #13#10;
  S := S + 'Sum of List2: ';
  Str(Sum(List2):4:2, TempStr);

  S := S + TempStr;
  MessageDlg(S, mtInformation, [mbOk], 0);

end;

Length(동적배열);

하시면 동적 배열의 크기가 나옵니다.