diff --git a/ddresc_visu/draw.py b/ddresc_visu/draw.py
index a9ffad0..f5f8e74 100644
--- a/ddresc_visu/draw.py
+++ b/ddresc_visu/draw.py
@@ -126,6 +126,10 @@ class Visualisation:
 				self.order = ['@', '+', '?', '-', '/', '*']
 				self.squares = None
 				self.draw()
+			if ev.type == pygame.KEYDOWN and ev.key == pygame.K_p:
+				sz = self.mapfile.size
+				sqsz = max(sz / CELLS, 4096)
+				print(f"Each square represents {sqsz} bytes.")
 			if ev.type == pygame.USEREVENT:
 				self.reload()