diff --git a/app/models/spree/stock/adjuster.rb b/app/models/spree/stock/adjuster.rb
new file mode 100644
index 0000000000..91e38ed345
--- /dev/null
+++ b/app/models/spree/stock/adjuster.rb
@@ -0,0 +1,28 @@
+# Used by Prioritizer to adjust item quantities
+# see prioritizer_spec for use cases
+module Spree
+  module Stock
+    class Adjuster
+      attr_accessor :variant, :need, :status
+
+      def initialize(variant, quantity, status)
+        @variant = variant
+        @need = quantity
+        @status = status
+      end
+
+      def adjust(item)
+        if item.quantity >= need
+          item.quantity = need
+          @need = 0
+        elsif item.quantity < need
+          @need -= item.quantity
+        end
+      end
+
+      def fulfilled?
+        @need == 0
+      end
+    end
+  end
+end
diff --git a/app/models/spree/stock/prioritizer.rb b/app/models/spree/stock/prioritizer.rb
new file mode 100644
index 0000000000..cdef38e043
--- /dev/null
+++ b/app/models/spree/stock/prioritizer.rb
@@ -0,0 +1,47 @@
+module Spree
+  module Stock
+    class Prioritizer
+      attr_reader :packages, :order
+
+      def initialize(order, packages, adjuster_class=Adjuster)
+        @order = order
+        @packages = packages
+        @adjuster_class = adjuster_class
+      end
+
+      def prioritized_packages
+        sort_packages
+        adjust_packages
+        prune_packages
+        packages
+      end
+
+      private
+      def adjust_packages
+        order.line_items.each do |line_item|
+          adjuster = @adjuster_class.new(line_item.variant, line_item.quantity, :on_hand)
+
+          visit_packages(adjuster)
+
+          adjuster.status = :backordered
+          visit_packages(adjuster)
+        end
+      end
+
+      def visit_packages(adjuster)
+        packages.each do |package|
+          item = package.find_item adjuster.variant, adjuster.status
+          adjuster.adjust(item) if item
+        end
+      end
+
+      def sort_packages
+        # order packages by preferred stock_locations
+      end
+
+      def prune_packages
+        packages.reject! { |pkg| pkg.empty? }
+      end
+    end
+  end
+end
diff --git a/spec/models/spree/stock/prioritizer_spec.rb b/spec/models/spree/stock/prioritizer_spec.rb
new file mode 100644
index 0000000000..52ce3ae97e
--- /dev/null
+++ b/spec/models/spree/stock/prioritizer_spec.rb
@@ -0,0 +1,111 @@
+require 'spec_helper'
+
+module Spree
+  module Stock
+    describe Prioritizer do
+      let(:order) { create(:order_with_line_items, line_items_count: 2) }
+      let(:stock_location) { build(:stock_location) }
+      let(:variant1) { order.line_items[0].variant }
+      let(:variant2) { order.line_items[1].variant }
+
+      def pack
+        package = Package.new(order, stock_location)
+        yield(package) if block_given?
+        package
+      end
+
+      it 'keeps a single package' do
+        package1 = pack do |package|
+          package.add variant1, 1, :on_hand
+          package.add variant2, 1, :on_hand
+        end
+
+        packages = [package1]
+        prioritizer = Prioritizer.new(order, packages)
+        packages = prioritizer.prioritized_packages
+        packages.size.should eq 1
+      end
+
+      it 'removes duplicate packages' do
+        package1 = pack do |package|
+          package.add variant1, 1, :on_hand
+          package.add variant2, 1, :on_hand
+        end
+        package2 = pack do |package|
+          package.add variant1, 1, :on_hand
+          package.add variant2, 1, :on_hand
+        end
+
+        packages = [package1, package2]
+        prioritizer = Prioritizer.new(order, packages)
+        packages = prioritizer.prioritized_packages
+        packages.size.should eq 1
+      end
+
+      it 'split over 2 packages' do
+        package1 = pack do |package|
+          package.add variant1, 1, :on_hand
+        end
+        package2 = pack do |package|
+          package.add variant2, 1, :on_hand
+        end
+
+        packages = [package1, package2]
+        prioritizer = Prioritizer.new(order, packages)
+        packages = prioritizer.prioritized_packages
+        packages.size.should eq 2
+      end
+
+      it '1st has some, 2nd has remaining' do
+        order.line_items[0].stub(:quantity => 5)
+        package1 = pack do |package|
+          package.add variant1, 2, :on_hand
+        end
+        package2 = pack do |package|
+          package.add variant1, 5, :on_hand
+        end
+
+        packages = [package1, package2]
+        prioritizer = Prioritizer.new(order, packages)
+        packages = prioritizer.prioritized_packages
+        packages.count.should eq 2
+        packages[0].quantity.should eq 2
+        packages[1].quantity.should eq 3
+      end
+
+      it '1st has backorder, 2nd has some' do
+        order.line_items[0].stub(:quantity => 5)
+        package1 = pack do |package|
+          package.add variant1, 5, :backordered
+        end
+        package2 = pack do |package|
+          package.add variant1, 2, :on_hand
+        end
+
+        packages = [package1, package2]
+        prioritizer = Prioritizer.new(order, packages)
+        packages = prioritizer.prioritized_packages
+
+        packages[0].quantity(:backordered).should eq 3
+        packages[1].quantity(:on_hand).should eq 2
+      end
+
+      it '1st has backorder, 2nd has all' do
+        order.line_items[0].stub(:quantity => 5)
+        package1 = pack do |package|
+          package.add variant1, 3, :backordered
+          package.add variant2, 1, :on_hand
+        end
+        package2 = pack do |package|
+          package.add variant1, 5, :on_hand
+        end
+
+        packages = [package1, package2]
+        prioritizer = Prioritizer.new(order, packages)
+        packages = prioritizer.prioritized_packages
+        packages[0].quantity(:backordered).should eq 0
+        packages[1].quantity(:on_hand).should eq 5
+      end
+    end
+  end
+end