diff --git a/src/nvfp4_megamoe_kernel/cutlass_nvfp4_gemm/cutlass_nvfp4_gemm.cu b/src/nvfp4_megamoe_kernel/cutlass_nvfp4_gemm/cutlass_nvfp4_gemm.cu
index 0dc6303a..5efce57f 100644
--- a/src/nvfp4_megamoe_kernel/cutlass_nvfp4_gemm/cutlass_nvfp4_gemm.cu
+++ b/src/nvfp4_megamoe_kernel/cutlass_nvfp4_gemm/cutlass_nvfp4_gemm.cu
@@ -137,10 +137,18 @@ __global__ void remap_sf_to_cutlass_kernel(
     constexpr int LayoutRank = cute::rank_v<decltype(layout_sf.shape())>;
 
     int dst_idx = 0;
+    // Use crd2idx to map flat logical coordinate to CUTLASS physical index.
+    // The layout's logical shape is ((32,4,...), (SFVecSize,4,...)) for K-major,
+    // but CuTe accepts flat coordinates and internally maps them.
+    // For SFA: logical coord is (m, k_element, l)
+    // For SFB: logical coord is (n, k_element, l)
+    // k_element = k_sf * InputSFVectorSize (convert SF group to K element)
     if constexpr (LayoutRank == 2) {
-        dst_idx = layout_sf(cute::make_coord(mn, k_sf * InputSFVectorSize));
+        auto logical_coord = cute::make_coord(mn, k_sf * InputSFVectorSize);
+        dst_idx = cute::crd2idx(logical_coord, layout_sf);
     } else if constexpr (LayoutRank == 3) {
-        dst_idx = layout_sf(cute::make_coord(mn, k_sf * InputSFVectorSize, 0));
+        auto logical_coord = cute::make_coord(mn, k_sf * InputSFVectorSize, 0);
+        dst_idx = cute::crd2idx(logical_coord, layout_sf);
     }
 
     int src_idx = mn * src_stride_mn + k_sf * src_stride_ksf;