diff --git a/lib/ai/formula_screen.dart b/lib/ai/formula_screen.dart
index 70e24ed..5bf88ec 100644
--- a/lib/ai/formula_screen.dart
+++ b/lib/ai/formula_screen.dart
@@ -211,6 +211,7 @@ class _FormulaScreenState extends State<FormulaScreen> {
               setState(() {
                 _selectedUnits[variable.name] = unit;
               });
+              _evaluateFormula();
             },
           ),
         ],