diff --git a/mud.c b/mud.c
index 1d72e5a..e248570 100644
--- a/mud.c
+++ b/mud.c
@@ -1246,6 +1246,9 @@ mud_update_window(struct mud *mud, struct mud_path *path,
                   uint64_t send_dt, uint64_t send_bytes,
                   uint64_t recv_dt, uint64_t recv_bytes)
 {
+    if (send_bytes && send_bytes >= recv_bytes)
+        path->loss = (send_bytes - recv_bytes) * 100 / send_bytes;
+
     // TODO
 }
 
diff --git a/mud.h b/mud.h
index c214d71..efd5dcc 100644
--- a/mud.h
+++ b/mud.h
@@ -36,6 +36,7 @@ struct mud_path {
     uint64_t window;
     uint64_t window_time;
     uint64_t window_size;
+    uint64_t loss;
     struct {
         size_t min;
         size_t max;