diff --git a/app/models/quantity.rb b/app/models/quantity.rb
index eb81c98..5e558b8 100644
--- a/app/models/quantity.rb
+++ b/app/models/quantity.rb
@@ -29,25 +29,9 @@ class Quantity < ActiveRecord::Base
     if new_record?
       self.domain ||= :diet
     end
-    @formula = Formula.new(self.project, self.formula)
   end
 
-  def formula=(value)
-    @formula = Formula.new(self.project, value)
-    super(value)
-  end
-
-  def formula_valid?
-    @formula.valid?
-  end
-
-  def formula_quantities
-    @formula.get_quantities
-  end
-
-  def calculate(inputs)
-    @formula.calculate(inputs)
-  end
+  delegate :valid?, :quantities, :calculate, to: :f_obj, prefix: :formula, allow_nil: true
 
   def movable?(direction)
     case direction
@@ -74,4 +58,10 @@ class Quantity < ActiveRecord::Base
 
     quantities
   end
+
+  private
+
+  def f_obj
+    Formula.new(self.project, self.formula) if self.formula?
+  end
 end
diff --git a/lib/body_tracking/formula.rb b/lib/body_tracking/formula.rb
index bfd63ef..de3e702 100644
--- a/lib/body_tracking/formula.rb
+++ b/lib/body_tracking/formula.rb
@@ -8,7 +8,7 @@ module BodyTracking
 
     class Formula
       def initialize(project, formula)
-        @project_quantities = Quantity.where(project: project)
+        @project = project
         @formula = formula
         @parts = nil
         @quantities = nil
@@ -19,7 +19,7 @@ module BodyTracking
         identifiers, parts = parser.parse
         errors = parser.errors
 
-        quantities = @project_quantities.where(name: identifiers)
+        quantities = Quantity.where(project: @project, name: identifiers)
         quantities_names = quantities.pluck(:name)
         (identifiers - quantities_names).each do |q|
           errors << [:unknown_quantity, {quantity: q}]
@@ -33,27 +33,24 @@ module BodyTracking
         @quantities || self.validate.empty?
       end
 
-      def get_quantities
+      def quantities
         raise(InvalidFormula, 'Invalid formula') unless self.valid?
 
         @quantities.to_a
       end
 
       def calculate(inputs)
-        byebug
-        params = inputs.map { |q, v| [q.name, v.transpose[0]] }.to_h
-        length = params.values.first.length
+        quantities = inputs.map { |q, v| [q.name, v.transpose[0]] }.to_h
+        length = quantities.values.first.length
 
         raise(InvalidFormula, 'Invalid formula') unless self.valid?
-        raise InvalidInputs unless params.values.all? { |v| v.length == length }
+        raise InvalidInputs unless quantities.values.all? { |v| v.length == length }
 
         args = []
         @parts.each do |p|
-          args << get_binding(params, length)
-            .eval(
-              p[:type] == :indexed ? "length.times.map { |_index| #{p[:content]} }" :
-                p[:content]
-            )
+          code = p[:type] == :indexed ?
+            "length.times.map { |index| #{p[:content]} }" : p[:content]
+          args << get_binding(quantities, args, length).eval(code)
         end
         args.last.map { |v| [v, nil] }
       rescue Exception => e
@@ -63,7 +60,7 @@ module BodyTracking
 
       private
 
-      def get_binding(params, _length)
+      def get_binding(quantities, args, length)
         binding
       end
     end
@@ -206,7 +203,7 @@ module BodyTracking
                        content: "quantities['#{left[1]}']#{dot.to_s}#{method}"}
             [:bt_quantity_method_call, "parts[#{part_index}]", part_index]
           else
-            [:bt_numeric_method_call, "quantities['#{left[1]}'][_index]#{dot.to_s}#{method}"]
+            [:bt_numeric_method_call, "quantities['#{left[1]}'][index]#{dot.to_s}#{method}"]
           end
         when :bt_quantity_method_call
           if mtype == :quantity_method
@@ -258,7 +255,7 @@ module BodyTracking
         [
           :bt_expression,
           [left, right].map do |side|
-            side[0] == :bt_quantity ? "quantities['#{side[1]}'][_index]" : "#{side[1]}"
+            side[0] == :bt_quantity ? "quantities['#{side[1]}'][index]" : "#{side[1]}"
           end.join(op.to_s)
         ]
       end
@@ -310,7 +307,7 @@ module BodyTracking
           when :bt_expression, :bt_numeric_method_call
             token
           when :bt_quantity
-            "quantities['#{token}'][_index]"
+            "quantities['#{token}'][index]"
           else
             raise NotImplementedError, stmt.inspect
           end
diff --git a/lib/body_tracking/items_with_quantities.rb b/lib/body_tracking/items_with_quantities.rb
index 919c3db..48966c3 100644
--- a/lib/body_tracking/items_with_quantities.rb
+++ b/lib/body_tracking/items_with_quantities.rb
@@ -83,10 +83,9 @@ module BodyTracking
         # quantity with formula has all dependencies satisfied, requires calculation
         if deps.empty?
           output_ids = items.select { |i| subitems[q.name][i.id].nil? }.map(&:id)
-        byebug
           input_q = q.formula_quantities
           inputs = input_q.map { |i_q| [i_q, completed_q[i_q.name].values_at(*output_ids)] }
-          q.calculate(inputs.to_h).each_with_index do |result, index|
+          q.formula_calculate(inputs.to_h).each_with_index do |result, index|
             subitems[q.name][output_ids[index]] = result
           end
           unchecked_q.unshift([q, deps])