diff --git a/app/models/formula.rb b/app/models/formula.rb
index 341a8be..cd82a37 100644
--- a/app/models/formula.rb
+++ b/app/models/formula.rb
@@ -17,6 +17,66 @@ class Formula < ActiveRecord::Base
     end
   end
 
+  def self.resolve(quantities, items, subitems)
+    unchecked_q = quantities.map { |q| [q, nil] }
+
+    # TODO: jesli wartosci nie ma w subitems to pytac w yield (jesli jest block)
+    completed_q = {}
+    # FIXME: loop should finish unless there is circular dependency in formulas
+    # for now we don't guard against that
+    while !unchecked_q.empty?
+      q, deps = unchecked_q.shift
+
+      # quantity not computable: no formula/invalid formula (syntax error/runtime error)
+      # or not requiring calculation/computed
+      if !q.formula || q.formula.errors.any? || !q.formula.valid? ||
+          (subitems[q].length == items.count)
+        completed_q[q] = subitems.delete(q) { {} }
+        next
+      end
+
+      # quantity with formula requires refresh of dependencies availability
+      if deps.nil? || !deps.empty?
+        deps ||= q.formula.quantities.clone
+        deps.reject! { |d| completed_q.has_key?(d) }
+        deps.each { |d| unchecked_q << [d, nil] unless unchecked_q.index { |u| u[0] == d } }
+      end
+
+      # quantity with formula has all dependencies satisfied, requires calculation
+      if deps.empty?
+        output_items = items.select { |i| subitems[q][i].nil? }
+        input_q = q.formula.quantities
+        inputs = input_q.map do |i_q|
+          values = completed_q[i_q].values_at(*output_items).map { |v| v || [nil, nil] }
+          values.map! { |v, u| [v || BigDecimal(0), u] } if q.formula.zero_nil
+          [i_q, values]
+        end
+        begin
+          calculated = q.formula.calculate(inputs.to_h)
+        rescue Exception => e
+          output_items.each { |o_i| subitems[q][o_i] = nil }
+          q.formula.errors.add(
+            :code, :computation_failed,
+            {
+              quantity: q.name,
+              description: e.message,
+              count: output_items.size == subitems[q].size ? 'all' : output_items.size
+            }
+          )
+        else
+          output_items.each_with_index { |o_i, idx| subitems[q][o_i] = calculated[idx] }
+        end
+        unchecked_q.unshift([q, deps])
+        next
+      end
+
+      # quantity still has unsatisfied dependencies, move to the end of queue
+      unchecked_q << [q, deps]
+    end
+
+    completed_q
+  end
+
   def calculate(inputs)
     raise(InvalidInputs, 'No inputs') if inputs.empty?
 
diff --git a/lib/body_tracking/items_with_quantities.rb b/lib/body_tracking/items_with_quantities.rb
index 4ca54bf..5b5a092 100644
--- a/lib/body_tracking/items_with_quantities.rb
+++ b/lib/body_tracking/items_with_quantities.rb
@@ -52,9 +52,6 @@ module BodyTracking
 
     def compute_quantities(requested_q, filter_q = nil)
       items = all
-      requested_q ||= Quantity.none
-      unchecked_q = requested_q.map { |q| [q, nil] }
-      unchecked_q << [filter_q, nil] if filter_q
 
       relations = RELATIONS[proxy_association.klass.name]
       subitems = Hash.new { |h,k| h[k] = {} }
@@ -66,58 +63,8 @@ module BodyTracking
         subitems[s.quantity][item] = [subitem_value, s.unit]
       end
 
-      completed_q = {}
-      # FIXME: loop should finish unless there is circular dependency in formulas
-      # for now we don't guard against that
-      while !unchecked_q.empty?
-        q, deps = unchecked_q.shift
-
-        # quantity not computable: no formula/invalid formula (syntax error/runtime error)
-        # or not requiring calculation/computed
-        if !q.formula || q.formula.errors.any? || !q.formula.valid? ||
-            (subitems[q].length == items.count)
-          completed_q[q] = subitems.delete(q) { {} }
-          next
-        end
-
-        # quantity with formula requires refresh of dependencies availability
-        if deps.nil? || !deps.empty?
-          deps ||= q.formula.quantities.clone
-          deps.reject! { |d| completed_q.has_key?(d) }
-          deps.each { |d| unchecked_q << [d, nil] unless unchecked_q.index { |u| u[0] == d } }
-        end
-
-        # quantity with formula has all dependencies satisfied, requires calculation
-        if deps.empty?
-          output_items = items.select { |i| subitems[q][i].nil? }
-          input_q = q.formula.quantities
-          inputs = input_q.map do |i_q|
-            values = completed_q[i_q].values_at(*output_items).map { |v| v || [nil, nil] }
-            values.map! { |v, u| [v || BigDecimal(0), u] } if q.formula.zero_nil
-            [i_q, values]
-          end
-          begin
-            calculated = q.formula.calculate(inputs.to_h)
-          rescue Exception => e
-            output_items.each { |o_i| subitems[q][o_i] = nil }
-            q.formula.errors.add(
-              :code, :computation_failed,
-              {
-                quantity: q.name,
-                description: e.message,
-                count: output_items.size == subitems[q].size ? 'all' : output_items.size
-              }
-            )
-          else
-            output_items.each_with_index { |o_i, idx| subitems[q][o_i] = calculated[idx] }
-          end
-          unchecked_q.unshift([q, deps])
-          next
-        end
-
-        # quantity still has unsatisfied dependencies, move to the end of queue
-        unchecked_q << [q, deps]
-      end
+      quantities = (requested_q || Quantity.none) + Array(filter_q)
+      completed_q = Formula.resolve(quantities, items, subitems)
 
       filter_values = completed_q.delete(filter_q)
       items.to_a.keep_if { |i| filter_values[i][0] } if filter_values