diff --git a/app/controllers/spree/admin/shipping_methods_controller.rb b/app/controllers/spree/admin/shipping_methods_controller.rb
index 5fa427772e..b91f8432a9 100644
--- a/app/controllers/spree/admin/shipping_methods_controller.rb
+++ b/app/controllers/spree/admin/shipping_methods_controller.rb
@@ -84,13 +84,13 @@ module Spree
 
       def permitted_resource_params
         params.require(:shipping_method).permit(
-          :name, :description, :display_on,
-          :require_ship_address, :tag_list, :calculator_type,
+          :name, :description, :display_on, :require_ship_address, :tag_list, :calculator_type,
           distributor_ids: [],
           calculator_attributes: [
-            :id, :preferred_currency, :preferred_amount, :preferred_per_kg, :preferred_flat_percent,
-            :preferred_first_item, :preferred_additional_item, :preferred_max_items,
-            :preferred_minimal_amount, :preferred_normal_amount, :preferred_discount_amount
+            :id, :preferred_currency, :preferred_amount, :preferred_unit_from_list,
+            :preferred_per_unit, :preferred_flat_percent, :preferred_first_item,
+            :preferred_additional_item, :preferred_max_items, :preferred_minimal_amount,
+            :preferred_normal_amount, :preferred_discount_amount
           ]
         )
       end
diff --git a/app/helpers/spree/admin/base_helper.rb b/app/helpers/spree/admin/base_helper.rb
index 6ffdc3dc2b..157762e823 100644
--- a/app/helpers/spree/admin/base_helper.rb
+++ b/app/helpers/spree/admin/base_helper.rb
@@ -45,14 +45,14 @@ module Spree
         end
       end
 
-      def preference_field_for(form, field, options)
+      def preference_field_for(form, field, options, object)
         case options[:type]
         when :integer
           form.text_field(field, preference_field_options(options))
         when :boolean
           form.check_box(field, preference_field_options(options))
         when :string
-          form.text_field(field, preference_field_options(options))
+          preference_field_for_text_field(form, field, options, object)
         when :password
           form.password_field(field, preference_field_options(options))
         when :text
@@ -62,6 +62,21 @@ module Spree
         end
       end
 
+      # Here we show a text field for all string fields except when the field name ends in
+      # "_from_list", in that case we render a dropdown.
+      # In this specific case, to render the dropdown, the object provided must have a method named
+      # like "#{field}_values" that returns an array with the string options to be listed.
+      def preference_field_for_text_field(form, field, options, object)
+        if field.end_with?('_from_list') && object.respond_to?("#{field}_values")
+          list_values = object.__send__("#{field}_values")
+          selected_value = object.__send__(field)
+          form.select(field, options_for_select(list_values, selected_value),
+                      preference_field_options(options))
+        else
+          form.text_field(field, preference_field_options(options))
+        end
+      end
+
       def preference_field_options(options)
         field_options = case options[:type]
                         when :integer
@@ -91,13 +106,21 @@ module Spree
         )
       end
 
+      # maps each preference to a hash containing the label and field html.
+      # E.g. { :label => "<label>...", :field => "<select>..." }
       def preference_fields(object, form)
         return unless object.respond_to?(:preferences)
 
-        object.preferences.keys.map{ |key|
-          form.label("preferred_#{key}", Spree.t(key) + ": ") +
-            preference_field_for(form, "preferred_#{key}", type: object.preference_type(key))
-        }.join("<br />").html_safe
+        object.preferences.keys.map { |key|
+          preference_label = form.label("preferred_#{key}",
+                                        Spree.t(key.to_s.gsub("_from_list", "")) + ": ").html_safe
+          preference_field = preference_field_for(
+            form,
+            "preferred_#{key}",
+            { type: object.preference_type(key) }, object
+          ).html_safe
+          { label: preference_label, field: preference_field }
+        }
       end
 
       def link_to_add_fields(name, target, options = {})
diff --git a/app/models/calculator/weight.rb b/app/models/calculator/weight.rb
index bb1f70c030..f4f451b785 100644
--- a/app/models/calculator/weight.rb
+++ b/app/models/calculator/weight.rb
@@ -3,16 +3,30 @@ require 'spree/localized_number'
 module Calculator
   class Weight < Spree::Calculator
     extend Spree::LocalizedNumber
-    preference :per_kg, :decimal, default: 0.0
-    localize_number :preferred_per_kg
+    preference :unit_from_list, :string, default: "kg"
+    preference :per_unit, :decimal, default: 0.0
+
+    localize_number :preferred_per_unit
 
     def self.description
       I18n.t('spree.weight')
     end
 
+    def set_preference(name, value)
+      if name == :unit_from_list && !["kg", "lb"].include?(value)
+        calculable.errors.add(:preferred_unit_from_list, I18n.t(:calculator_preferred_unit_error))
+      else
+        __send__ self.class.preference_setter_method(name), value
+      end
+    end
+
     def compute(object)
       line_items = line_items_for object
-      (total_weight(line_items) * preferred_per_kg).round(2)
+      (total_weight(line_items) * preferred_per_unit).round(2)
+    end
+
+    def preferred_unit_from_list_values
+      ["kg", "lb"]
     end
 
     private
@@ -33,8 +47,8 @@ module Calculator
 
     def weight_per_variant(line_item)
       if variant_unit(line_item) == 'weight'
-        # The calculator price is per_kg so we need to convert unit_value to kg
-        convert_g_to_kg(line_item.variant.andand.unit_value)
+        # Convert unit_value to the preferred unit
+        convert_weight(line_item.variant.andand.unit_value)
       else
         line_item.variant.andand.weight || 0
       end
@@ -42,8 +56,8 @@ module Calculator
 
     def weight_per_final_weight_volume(line_item)
       if variant_unit(line_item) == 'weight'
-        # The calculator price is per_kg so we need to convert final_weight_volume to kg
-        convert_g_to_kg(line_item.final_weight_volume)
+        # Convert final_weight_volume to the preferred unit
+        convert_weight(line_item.final_weight_volume)
       else
         weight_per_variant(line_item) * quantity_implied_in_final_weight_volume(line_item)
       end
@@ -66,10 +80,14 @@ module Calculator
       line_item.variant.product.andand.variant_unit
     end
 
-    def convert_g_to_kg(value)
-      return 0 unless value
+    def convert_weight(value)
+      return 0 unless value && ["kg", "lb"].include?(preferences[:unit_from_list])
 
-      value / 1000
+      if preferences[:unit_from_list] == "kg"
+        value / 1000
+      elsif preferences[:unit_from_list] == "lb"
+        value / 453.6
+      end
     end
   end
 end
diff --git a/app/views/admin/enterprise_fees/_calculator_settings.html.haml b/app/views/admin/enterprise_fees/_calculator_settings.html.haml
index 45e2a7c394..f505f0c38a 100644
--- a/app/views/admin/enterprise_fees/_calculator_settings.html.haml
+++ b/app/views/admin/enterprise_fees/_calculator_settings.html.haml
@@ -7,6 +7,10 @@
       - if !enterprise_fee.new_record?
         .calculator-settings
           = f.fields_for :calculator do |calculator_form|
-            = preference_fields(enterprise_fee.calculator, calculator_form)
+            - preference_fields(enterprise_fee.calculator, calculator_form).each do |field|
+              .field.alpha.one.columns
+                = field[:label]
+              .field.omega.two.columns
+                = field[:field]
 
 = calculator_form_string
diff --git a/app/views/spree/admin/payment_methods/_provider_settings.html.haml b/app/views/spree/admin/payment_methods/_provider_settings.html.haml
index cbf24630b2..f4f91b2ca8 100644
--- a/app/views/spree/admin/payment_methods/_provider_settings.html.haml
+++ b/app/views/spree/admin/payment_methods/_provider_settings.html.haml
@@ -10,4 +10,8 @@
         = t(:provider_settings)
       .preference-settings
         = fields_for :payment_method, @payment_method do |payment_method_form|
-          = preference_fields(@payment_method, payment_method_form)
+          - preference_fields(@payment_method, payment_method_form).each do |field|
+            .field.alpha.three.columns
+              = field[:label]
+            .field.omega.eight.columns
+              = field[:field]
diff --git a/app/views/spree/admin/shared/_calculator_fields.html.haml b/app/views/spree/admin/shared/_calculator_fields.html.haml
index 062503c8d6..227c13bb45 100644
--- a/app/views/spree/admin/shared/_calculator_fields.html.haml
+++ b/app/views/spree/admin/shared/_calculator_fields.html.haml
@@ -2,12 +2,18 @@
   %legend{align: "center"}= t(:calculator)
   #preference-settings
     .field
-      = f.label(:calculator_type, t(:calculator), for: 'calc_type')
-      = f.select(:calculator_type, @calculators.map { |c| [c.description, c.name] }, {}, {id: 'calc_type', class: 'select2 fullwidth'})
+      .alpha.three.columns
+        = f.label(:calculator_type, t(:calculator), for: 'calc_type')
+      .omega.eight.columns
+        = f.select(:calculator_type, @calculators.map { |c| [c.description, c.name] }, {}, {id: 'calc_type', class: 'select2 fullwidth'})
     - if !@object.new_record?
       .field
         .calculator-settings
           = f.fields_for :calculator do |calculator_form|
-            = preference_fields(@object.calculator, calculator_form)
+            - preference_fields(@object.calculator, calculator_form).each do |field|
+              .field.alpha.three.columns
+                = field[:label]
+              .field.omega.eight.columns
+                = field[:field]
         - if @object.calculator.respond_to?(:preferences)
           %span.calculator-settings-warning.info.warning= t(:calculator_settings_warning)
diff --git a/app/views/spree/admin/shipping_methods/_form.html.haml b/app/views/spree/admin/shipping_methods/_form.html.haml
index 13d7667745..b03085c7a0 100644
--- a/app/views/spree/admin/shipping_methods/_form.html.haml
+++ b/app/views/spree/admin/shipping_methods/_form.html.haml
@@ -44,8 +44,7 @@
       %tags-with-translation#something{ object: "shippingMethod", 'find-tags' => 'findTags(query)' }
 
   .row
-    .alpha.eleven.columns
-      = render partial: 'spree/admin/shared/calculator_fields', locals: { f: f }
+    = render partial: 'spree/admin/shared/calculator_fields', locals: { f: f }
 
   .row
     .alpha.eleven.columns
diff --git a/config/locales/en.yml b/config/locales/en.yml
index fa966a815b..5979a77a97 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -2125,6 +2125,7 @@ See the %{link} to find out more about %{sitename}'s features and to start using
   calculator: "Calculator"
   calculator_values: "Calculator values"
   calculator_settings_warning: "If you are changing the calculator type, you must save first before you can edit the calculator settings"
+  calculator_preferred_unit_error: "must be kg or lb"
   flat_percent_per_item: "Flat Percent (per item)"
   flat_rate_per_item: "Flat Rate (per item)"
   flat_rate_per_order: "Flat Rate (per order)"
@@ -3146,7 +3147,7 @@ See the %{link} to find out more about %{sitename}'s features and to start using
     inventory_error_flash_for_insufficient_quantity: "An item in your cart has become unavailable."
     inventory: Inventory
     zipcode: Postcode
-    weight: Weight (per kg)
+    weight: Weight (per kg or lb)
     error_user_destroy_with_orders: "Users with completed orders may not be deleted"
     cannot_create_payment_without_payment_methods: "You cannot create a payment for an order without any payment methods defined."
     please_define_payment_methods: "Please define some payment methods first."
diff --git a/db/migrate/20200912190210_update_weight_calculators.rb b/db/migrate/20200912190210_update_weight_calculators.rb
new file mode 100644
index 0000000000..2a24138957
--- /dev/null
+++ b/db/migrate/20200912190210_update_weight_calculators.rb
@@ -0,0 +1,13 @@
+class UpdateWeightCalculators < ActiveRecord::Migration
+  def change
+    Spree::Calculator.connection.execute(
+      "UPDATE spree_preferences SET key = replace( key, 'per_kg', 'per_unit') WHERE key ilike '/calculator/weight/per_kg/%'"
+    )
+
+    Calculator::Weight.all.each { |calculator|
+      calculator.preferred_unit_from_list = 'kg'
+      Rails.cache.delete("/calculator/weight/per_kg/#{calculator.id}")
+      calculator.save
+    }
+  end
+end
diff --git a/spec/controllers/spree/admin/shipping_methods_controller_spec.rb b/spec/controllers/spree/admin/shipping_methods_controller_spec.rb
index f209e87a81..2c1fa2c0b6 100644
--- a/spec/controllers/spree/admin/shipping_methods_controller_spec.rb
+++ b/spec/controllers/spree/admin/shipping_methods_controller_spec.rb
@@ -29,13 +29,22 @@ describe Spree::Admin::ShippingMethodsController, type: :controller do
       expect(shipping_method.reload.calculator.preferred_currency).to eq "EUR"
     end
 
-    it "updates preferred_per_kg of a Weight calculator" do
+    it "updates preferred_per_unit of a Weight calculator" do
       shipping_method.calculator = create(:weight_calculator, calculable: shipping_method)
-      params[:shipping_method][:calculator_attributes][:preferred_per_kg] = 10
+      params[:shipping_method][:calculator_attributes][:preferred_per_unit] = 10
 
       spree_post :update, params
 
-      expect(shipping_method.reload.calculator.preferred_per_kg).to eq 10
+      expect(shipping_method.reload.calculator.preferred_per_unit).to eq 10
+    end
+
+    it "updates preferred_unit of a Weight calculator" do
+      shipping_method.calculator = create(:weight_calculator, calculable: shipping_method)
+      params[:shipping_method][:calculator_attributes][:preferred_unit_from_list] = "kg"
+
+      spree_post :update, params
+
+      expect(shipping_method.reload.calculator.preferred_unit_from_list).to eq "kg"
     end
 
     it "updates preferred_flat_percent of a FlatPercentPerItem calculator" do
diff --git a/spec/factories/calculator_factory.rb b/spec/factories/calculator_factory.rb
index 1268a8ccb7..1203d5b52c 100644
--- a/spec/factories/calculator_factory.rb
+++ b/spec/factories/calculator_factory.rb
@@ -13,7 +13,14 @@ FactoryBot.define do
   end
 
   factory :weight_calculator, class: Calculator::Weight do
-    after(:build)  { |c| c.set_preference(:per_kg, 0.5) }
-    after(:create) { |c| c.set_preference(:per_kg, 0.5); c.save! }
+    after(:build)  { |c|
+      c.set_preference(:per_unit, 0.5)
+      c.set_preference(:unit_from_list, "kg")
+    }
+    after(:create) { |c|
+      c.set_preference(:per_unit, 0.5)
+      c.set_preference(:unit_from_list, "kg")
+      c.save!
+    }
   end
 end
diff --git a/spec/features/consumer/shopping/cart_spec.rb b/spec/features/consumer/shopping/cart_spec.rb
index 5339aa99f7..d702ce7067 100644
--- a/spec/features/consumer/shopping/cart_spec.rb
+++ b/spec/features/consumer/shopping/cart_spec.rb
@@ -118,7 +118,7 @@ feature "full-page cart", js: true do
     describe "admin weight calculated fees" do
       context "order with 2 line items" do
         let(:admin_fee) {
-          create(:enterprise_fee, calculator: Calculator::Weight.new(preferred_per_kg: 1),
+          create(:enterprise_fee, calculator: Calculator::Weight.new(preferred_per_unit: 1, preferred_unit_from_list: "kg"),
                                   enterprise: order_cycle.coordinator, fee_type: 'admin')
         }
 
diff --git a/spec/models/calculator/weight_spec.rb b/spec/models/calculator/weight_spec.rb
index 2359b28e09..1016af2eaa 100644
--- a/spec/models/calculator/weight_spec.rb
+++ b/spec/models/calculator/weight_spec.rb
@@ -1,7 +1,7 @@
 require 'spec_helper'
 
 describe Calculator::Weight do
-  it_behaves_like "a model using the LocalizedNumber module", [:preferred_per_kg]
+  it_behaves_like "a model using the LocalizedNumber module", [:preferred_per_unit]
 
   it "computes shipping cost for an order by total weight" do
     variant1 = build_stubbed(:variant, unit_value: 10_000)
@@ -14,7 +14,8 @@ describe Calculator::Weight do
 
     order = double(:order, line_items: [line_item1, line_item2, line_item3])
 
-    subject.set_preference(:per_kg, 5)
+    subject.set_preference(:per_unit, 5)
+    subject.set_preference(:unit_from_list, "kg")
     expect(subject.compute(order)).to eq(350) # (10 * 1 + 20 * 3) * 5
   end
 
@@ -22,7 +23,10 @@ describe Calculator::Weight do
     let(:variant) { build_stubbed(:variant, unit_value: 10_000) }
     let(:line_item) { build_stubbed(:line_item, variant: variant, quantity: 2) }
 
-    before { subject.set_preference(:per_kg, 5) }
+    before {
+      subject.set_preference(:per_unit, 5)
+      subject.set_preference(:unit_from_list, "kg")
+    }
 
     it "computes shipping cost for a line item" do
       expect(subject.compute(line_item)).to eq(100) # 10 * 2 * 5
@@ -57,15 +61,18 @@ describe Calculator::Weight do
     order = double(:order, line_items: [line_item1, line_item2])
     object_with_order = double(:object_with_order, order: order)
 
-    subject.set_preference(:per_kg, 5)
+    subject.set_preference(:per_unit, 5)
+    subject.set_preference(:unit_from_list, "kg")
     expect(subject.compute(object_with_order)).to eq(250) # (10 * 1 + 20 * 2) * 5
+    subject.set_preference(:unit_from_list, "lb")
+    expect(subject.compute(object_with_order)).to eq(551.15) # (10 * 1 + 20 * 2) * 5 * 2.2
   end
 
   context "when line item final_weight_volume is set" do
     let!(:product) { build_stubbed(:product, product_attributes) }
     let!(:variant) { build_stubbed(:variant, variant_attributes.merge(product: product)) }
 
-    let(:calculator) { described_class.new(preferred_per_kg: 6) }
+    let(:calculator) { described_class.new(preferred_per_unit: 6, preferred_unit_from_list: "kg") }
     let(:line_item) do
       build_stubbed(:line_item, variant: variant, quantity: 2).tap do |object|
         object.send(:calculate_final_weight_volume)
@@ -182,7 +189,10 @@ describe Calculator::Weight do
     }
     let(:line_item) { build_stubbed(:line_item, variant: variant, quantity: 1) }
 
-    before { subject.set_preference(:per_kg, 5) }
+    before {
+      subject.set_preference(:per_unit, 5)
+      subject.set_preference(:unit_from_list, "kg")
+    }
 
     context "when unit_value is zero variant.weight is present" do
       let(:variant) { build_stubbed(:variant, product: product, unit_value: 0, weight: 10.0) }
@@ -224,4 +234,20 @@ describe Calculator::Weight do
       end
     end
   end
+
+  it "allows a preferred_unit of 'kg' and 'lb'" do
+    subject.calculable = build(:shipping_method)
+    subject.set_preference(:per_unit, 5)
+    subject.set_preference(:unit_from_list, "kg")
+    expect(subject.calculable.errors.count).to eq(0)
+    subject.set_preference(:unit_from_list, "lb")
+    expect(subject.calculable.errors.count).to eq(0)
+  end
+
+  it "does not allow a preferred_unit of anything but 'kg' or 'lb'" do
+    subject.calculable = build(:shipping_method)
+    subject.set_preference(:per_unit, 5)
+    subject.set_preference(:unit_from_list, "kb")
+    expect(subject.calculable.errors.count).to eq(1)
+  end
 end