diff --git a/core/renderer.py b/core/renderer.py
index 4948e4c..2bbca5c 100644
--- a/core/renderer.py
+++ b/core/renderer.py
@@ -164,7 +164,9 @@ class ExcelRenderer:
         bg_color = self._parse_color(fill_color, default=(255, 255, 255))
         
         # Draw background and border
-        draw.rectangle([x1, y1, x2, y2], fill=bg_color, outline=(200, 200, 200))
+        # Scale border width: at least 1px, roughly 1px per scale unit but kept thin for aesthetics
+        border_width = max(1, scale) 
+        draw.rectangle([x1, y1, x2, y2], fill=bg_color, outline=(200, 200, 200), width=border_width)
 
         # Content
         cell_value = cell.value