diff --git a/app/models/spree/calculator/flexi_rate_decorator.rb b/app/models/spree/calculator/flexi_rate_decorator.rb
index 04ad709cbe..d2b0457b44 100644
--- a/app/models/spree/calculator/flexi_rate_decorator.rb
+++ b/app/models/spree/calculator/flexi_rate_decorator.rb
@@ -15,12 +15,12 @@ module Spree
       sum = 0
       max = self.preferred_max_items.to_i
       items_count = line_items_for(object).map(&:quantity).sum
-      items_count.times do |i|
-        # check max value to avoid divide by 0 errors
-        if (max == 0 && i == 0) || (max > 0) && (i % max == 0)
-          sum += self.preferred_first_item.to_f
-        else
-          sum += self.preferred_additional_item.to_f
+      # check max value to avoid divide by 0 errors
+      unless max == 0
+        if items_count > max
+          sum += (max - 1) * self.preferred_additional_item.to_f + self.preferred_first_item.to_f
+        elsif items_count <= max
+          sum += (items_count - 1) * self.preferred_additional_item.to_f + self.preferred_first_item.to_f
         end
       end
 
diff --git a/spec/models/spree/calculator/flexi_rate_spec.rb b/spec/models/spree/calculator/flexi_rate_spec.rb
index 49c2371e13..6659da86fd 100644
--- a/spec/models/spree/calculator/flexi_rate_spec.rb
+++ b/spec/models/spree/calculator/flexi_rate_spec.rb
@@ -1,14 +1,29 @@
 require 'spec_helper'
 
 describe Spree::Calculator::FlexiRate do
-  let(:calculator) { Spree::Calculator::FlexiRate.new }
-  let(:line_item) { instance_double(Spree::LineItem, amount: 10, quantity: 4) }
+  let(:line_item) { instance_double(Spree::LineItem, amount: 10, quantity: quantity) }
+  let(:calculator) do
+    Spree::Calculator::FlexiRate.new(
+      preferred_first_item: 2,
+      preferred_additional_item: 1,
+      preferred_max_items: 3
+    )
+  end
 
-  describe "computing for a single line item" do
-    it "returns the first item rate" do
-      calculator.stub preferred_first_item: 1.0
-      calculator.compute(line_item).round(2).should == 1.0
-    end
+  context 'when nb of items ordered is above preferred max' do
+   let(:quantity) { 4.0 }
+
+   it "returns the first item rate" do
+     expect(calculator.compute(line_item).round(2)).to eq(4.0)
+   end
+  end
+
+  context 'when nb of items ordered is below preferred max' do
+   let(:quantity) { 2.0 }
+
+   it "returns the first item rate" do
+     expect(calculator.compute(line_item).round(2)).to eq(3.0)
+   end
   end
 
   it "allows creation of new object with all the attributes" do