diff --git a/example/ck_tile/01_fmha/fmha_fwd.cpp b/example/ck_tile/01_fmha/fmha_fwd.cpp
old mode 100644
new mode 100755
index bb1f495c4e..8958c0c96e
--- a/example/ck_tile/01_fmha/fmha_fwd.cpp
+++ b/example/ck_tile/01_fmha/fmha_fwd.cpp
@@ -542,8 +542,8 @@ bool run(const ck_tile::ArgParser& arg_parser)
                 max_seqlen_k = real_seqlen_k;
             }
 
-            flop += nhead * (static_cast<std::size_t>(2) * real_seqlen_q * real_seqlen_k * hdim_q +
-                             static_cast<std::size_t>(2) * real_seqlen_q * hdim_v * real_seqlen_k);
+            flop += nhead * (static_cast<std::size_t>(2) * mask.get_unmaskarea() * hdim_q +
+                             static_cast<std::size_t>(2) * mask.get_unmaskarea() * hdim_v);
 
             num_byte += nhead * (sizeof(QDataType) * real_seqlen_q * hdim_q +
                                  sizeof(KDataType) * real_seqlen_k * hdim_q +
diff --git a/example/ck_tile/01_fmha/mask.hpp b/example/ck_tile/01_fmha/mask.hpp
old mode 100644
new mode 100755
index c77b700b16..b96482f535
--- a/example/ck_tile/01_fmha/mask.hpp
+++ b/example/ck_tile/01_fmha/mask.hpp
@@ -21,6 +21,8 @@ enum class mask_enum
 struct mask_info
 {
     mask_enum type;
+    ck_tile::index_t seqlen_q;
+    ck_tile::index_t seqlen_k;
     ck_tile::index_t y, x;
     ck_tile::index_t left, right; // FA style SWA left/right
 
@@ -42,6 +44,8 @@ struct mask_info
         ck_tile::index_t x_total = seqlen_k;
         ck_tile::index_t y_total = seqlen_q;
         mask_info tmp;
+        tmp.seqlen_q = seqlen_q;
+        tmp.seqlen_k = seqlen_k;
         auto found_0 = str.find(':');
         if(found_0 != std::string::npos)
         {
@@ -148,7 +152,22 @@ struct mask_info
         }
         return tmp;
     }
-
+    ck_tile::index_t get_unmaskarea() const
+    {
+        if(type == mask_enum::no_mask)
+            return seqlen_q * seqlen_k;
+        ck_tile::index_t area = 0;
+        for(ck_tile::index_t i_y = 0; i_y < seqlen_q; ++i_y)
+        {
+            ck_tile::index_t x_start = std::max(-y + i_y + 1, static_cast<ck_tile::index_t>(0));
+            ck_tile::index_t x_end   = std::min(i_y + x, seqlen_k);
+            if(x_end > x_start)
+            {
+                area += (x_end - x_start);
+            }
+        }
+        return area;
+    }
     friend std::ostream& operator<<(std::ostream& os, const mask_info& mi)
     {
         mi.serialize(os);