diff --git a/calculator/main.py b/calculator/main.py
index d024794..e10414d 100644
--- a/calculator/main.py
+++ b/calculator/main.py
@@ -152,6 +152,11 @@ def read_item(
     average_hours_threshold:float=1.25,
     ) -> DayPrice:
     
+    # Convert hours to 15-min intervals
+    num_cheapest_hours *= 4
+    num_most_expensive_hours *= 4
+    average_hours *= 4
+    
     if not date:
         date = datetime.date.today()
     if not hour: