diff --git a/Controllers/Summary.Controller.cs b/Controllers/Summary.Controller.cs
index 871933a..4be1c24 100644
--- a/Controllers/Summary.Controller.cs
+++ b/Controllers/Summary.Controller.cs
@@ -484,10 +484,14 @@ namespace rmutr_report.Controllers
                 ws.Range("N2:O3").Style.Alignment.Vertical = XLAlignmentVerticalValues.Center;
                 ws.Range("N2:O3").Style.Border.OutsideBorder = XLBorderStyleValues.Thin;
                 ws.Cell("N2").Style.Alignment.WrapText = true;
+                int planRow = -1;
+                var outputRows = new List<int>();
+
                 foreach (var equipments in summary_of_equipments.header_data)
                 {
                     if (equipments.color == 1)
                     {
+                        planRow = row;
                         ws.Cell(row, 1).Value = null;
                         ws.Cell(row, 2).Value = equipments.list;
                         ws.Cell(row, 3).Value = null;
@@ -548,8 +552,13 @@ namespace rmutr_report.Controllers
                         row++;
                     }
 
+                    int outputRow = -1;
+                    var facultyRowsForOutput = new List<int>();
+
                     if (equipments.color == 2)
                     {
+                        outputRow = row;
+                        outputRows.Add(outputRow);
                         ws.Cell(row, 1).Value = null;
                         ws.Cell(row, 2).Value = equipments.list;
                         ws.Cell(row, 3).Value = null;
@@ -612,8 +621,13 @@ namespace rmutr_report.Controllers
 
                     foreach (var equipments1 in equipments.data)
                     {
+                        int facultyRow = -1;
+                        var areaRowsForFaculty = new List<int>();
+
                         if (equipments1.color == 3)
                         {
+                            facultyRow = row;
+                            facultyRowsForOutput.Add(facultyRow);
                             ws.Cell(row, 1).Value = null;
                             ws.Cell(row, 2).Value = equipments1.faculty_name;
                             ws.Cell(row, 3).Value = null;
@@ -677,8 +691,12 @@ namespace rmutr_report.Controllers
 
                         foreach (var equipments2 in equipments1.data)
                         {
+                            int areaRow = -1;
+
                             if (equipments2.color == 4)
                             {
+                                areaRow = row;
+                                areaRowsForFaculty.Add(areaRow);
                                 ws.Cell(row, 1).Value = null;
                                 ws.Cell(row, 2).Value = equipments2.list;
                                 ws.Cell(row, 3).Value = null;
@@ -740,6 +758,7 @@ namespace rmutr_report.Controllers
                             }
 
 
+                            int detailStartRow = row;
                             foreach (var equipment3 in equipments2.data)
                             {
                                 ws.Cell(row, 1).Value = no;
@@ -845,7 +864,43 @@ namespace rmutr_report.Controllers
 
                                 row++;
                             }
+                            // SUM formula: พื้นที่ (color=4) = SUM of detail rows
+                            if (areaRow != -1 && detailStartRow <= row - 1)
+                            {
+                                for (int c = 9; c <= 13; c++)
+                                {
+                                    string col = ((char)('A' + c - 1)).ToString();
+                                    ws.Cell(areaRow, c).FormulaA1 = $"SUM({col}{detailStartRow}:{col}{row - 1})";
+                                }
+                            }
                         }
+                        // SUM formula: คณะ (color=3) = SUM of area header rows
+                        if (facultyRow != -1 && areaRowsForFaculty.Count > 0)
+                        {
+                            for (int c = 9; c <= 13; c++)
+                            {
+                                string col = ((char)('A' + c - 1)).ToString();
+                                ws.Cell(facultyRow, c).FormulaA1 = $"SUM({string.Join(",", areaRowsForFaculty.Select(r => $"{col}{r}"))})";
+                            }
+                        }
+                    }
+                    // SUM formula: ผลผลิต (color=2) = SUM of faculty header rows
+                    if (outputRow != -1 && facultyRowsForOutput.Count > 0)
+                    {
+                        for (int c = 9; c <= 13; c++)
+                        {
+                            string col = ((char)('A' + c - 1)).ToString();
+                            ws.Cell(outputRow, c).FormulaA1 = $"SUM({string.Join(",", facultyRowsForOutput.Select(r => $"{col}{r}"))})";
+                        }
+                    }
+                }
+                // SUM formula: แผนงาน (color=1) = SUM of output header rows
+                if (planRow != -1 && outputRows.Count > 0)
+                {
+                    for (int c = 9; c <= 13; c++)
+                    {
+                        string col = ((char)('A' + c - 1)).ToString();
+                        ws.Cell(planRow, c).FormulaA1 = $"SUM({string.Join(",", outputRows.Select(r => $"{col}{r}"))})";
                     }
                 }
             }