diff --git a/backend/calculations/body_metrics.py b/backend/calculations/body_metrics.py
index 8a20d9a..af1a138 100644
--- a/backend/calculations/body_metrics.py
+++ b/backend/calculations/body_metrics.py
@@ -400,6 +400,10 @@ def _score_weight_trend(profile_id: str) -> Optional[int]:
     if None in [current, target]:
         return None
 
+    # Convert Decimal to float (PostgreSQL NUMERIC returns Decimal)
+    current = float(current)
+    target = float(target)
+
     # If no start_value, use oldest weight in last 90 days
     if start is None:
         with get_db() as conn:
@@ -414,6 +418,8 @@ def _score_weight_trend(profile_id: str) -> Optional[int]:
             """, (profile_id,))
             row = cur.fetchone()
             start = float(row['weight']) if row else current
+    else:
+        start = float(start)
 
     # Progress percentage
     progress_pct = calculate_goal_progress_pct(current, target, start)