You have to do it yourself, on the onResize event of your Grid parent

Use the ColWidth property to set the width of each individual columns
This algo is crude by the resize of each column proportionally, but that's the idea, you can do whatever you want from that, like have some columns with a fixed size...

procedure TForm1.FormResize(Sender: TObject);
Var
 i,TotCol:Integer;
begin
 TotCol:=0;
 for i:=0 to ColCount-1 do TotCol:=TotCol+sg1.ColWidths[i];
 for i:=0 to ColCount-1 do sg1.ColWidths[i]:=Trunc(sg1.ColWidths[i]/TotCol*sg1.Width);
end;

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The ColCount etc is for a tString Grid I am using a data TDBGrid is there any options for this  

Hi, use this function to automatically resize the columns of the DBGrid

procedure TForm1.AdjustColumnWidths(DBGrid: TDBGrid);
var
  TotalColumnWidth, ColumnCount, GridClientWidth, Filler, i: Integer;
begin
  ColumnCount := DBGrid.Columns.Count;
  if ColumnCount = 0 then
    Exit;
  TotalColumnWidth := 0;
  for i := 0 to ColumnCount - 1 do
    TotalColumnWidth := TotalColumnWidth + DBGrid.Columns[i].Width;
  if dgColLines in DBGrid.Options then
    TotalColumnWidth := TotalColumnWidth + ColumnCount;
  GridClientWidth := DBGrid.Width - GetSystemMetrics(SM_CXVSCROLL);
  if dgIndicator in DBGrid.Options then
  begin
    GridClientWidth := GridClientWidth - IndicatorWidth;
    if dgColLines in DBGrid.Options then
      Dec(GridClientWidth);
  end;
  if DBGrid.BorderStyle = bsSingle then
  begin
    if DBGrid.Ctl3D then
      GridClientWidth := GridClientWidth - 4
    else
      GridClientWidth := GridClientWidth - 2;
  end;
  if TotalColumnWidth < GridClientWidth then
  begin
    Filler := (GridClientWidth - TotalColumnWidth) div ColumnCount;
    for i := 0 to ColumnCount - 1 do
      DBGrid.Columns[i].Width := DBGrid.Columns[i].Width + Filler;
  end
  else if TotalColumnWidth > GridClientWidth then
  begin
    Filler := (TotalColumnWidth - GridClientWidth) div ColumnCount;
    if (TotalColumnWidth - GridClientWidth) mod ColumnCount <> 0 then
      Inc(Filler);
    for i := 0 to ColumnCount - 1 do
      DBGrid.Columns[i].Width := DBGrid.Columns[i].Width - Filler;
  end;
end;

Hi, use it like this, as @epasquier suggested too...

procedure TForm1.FormResize(Sender: TObject);
begin
 AdjustColumnWidths(DBGrid1);
end;

Hi I added the code and the tForm1.resize code and changed the name DBGrid1 to GrdAuto which is the TDBGrid name and I makes no change to the grid column sizes

Hi, make sure that in the Anchors property of the dbgid both akLeft and akRight properties are set to true. I' ve tested the code and it works fine with me...

Im using Delphi 5 and all the anchor properties are set to true
ive tried setting the bottom top to false and any other combination

Still not working but I am upgrading to delphi 10