diff --git a/app/models/case_log.rb b/app/models/case_log.rb
index 7ceeaecdc..a5cc2eff7 100644
--- a/app/models/case_log.rb
+++ b/app/models/case_log.rb
@@ -133,7 +133,7 @@ class CaseLog < ApplicationRecord
   enum postcode_known: POLAR, _suffix: true
   enum la_known: POLAR, _suffix: true
 
-  AUTOGENERATED_FIELDS = %w[id status created_at updated_at discarded_at renttype lettype is_la_inferred totchild totelder].freeze
+  AUTOGENERATED_FIELDS = %w[id status created_at updated_at discarded_at renttype lettype is_la_inferred totchild totelder totadult].freeze
   OPTIONAL_FIELDS = %w[postcode_known
                        la_known
                        first_time_property_let_as_social_housing].freeze
@@ -215,6 +215,7 @@ private
     self.la = get_la(property_postcode)
     self.totchild = get_totchild
     self.totelder = get_totelder
+    self.totadult = get_totadult
   end
 
   def get_totelder
@@ -227,6 +228,17 @@ private
     relationships.count("Child - includes young adult and grown-up")
   end
 
+  def get_totadult
+    total = !age1.nil? && age1 >= 16 && age1 < 60 ? 1 : 0
+    total + (2..8).count do |i|
+      # rubocop:disable Style/EvalWithLocation, Security/Eval::
+      age = eval("age#{i}")
+      relat = eval("relat#{i}")
+      # rubocop:enable Style/EvalWithLocation, Security/Eval::
+      !age.nil? && ((age >= 16 && age < 18 && %w[Partner Other].include?(relat)) || age >= 18 && age < 60)
+    end
+  end
+
   def get_la(postcode)
     if postcode.present?
       postcode_lookup = PIO.lookup(postcode)
diff --git a/db/migrate/20211214163230_add_totadult.rb b/db/migrate/20211214163230_add_totadult.rb
new file mode 100644
index 000000000..1dc8e1367
--- /dev/null
+++ b/db/migrate/20211214163230_add_totadult.rb
@@ -0,0 +1,7 @@
+class AddTotadult < ActiveRecord::Migration[6.1]
+  def change
+    change_table :case_logs, bulk: true do |t|
+      t.column :totadult, :integer
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 17a7babce..242c019fe 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2021_12_14_153925) do
+ActiveRecord::Schema.define(version: 2021_12_14_163230) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -177,6 +177,7 @@ ActiveRecord::Schema.define(version: 2021_12_14_153925) do
     t.integer "year"
     t.integer "totchild"
     t.integer "totelder"
+    t.integer "totadult"
     t.index ["discarded_at"], name: "index_case_logs_on_discarded_at"
     t.index ["managing_organisation_id"], name: "index_case_logs_on_managing_organisation_id"
     t.index ["owning_organisation_id"], name: "index_case_logs_on_owning_organisation_id"
diff --git a/spec/models/case_log_spec.rb b/spec/models/case_log_spec.rb
index ae17489fb..7b82ecd90 100644
--- a/spec/models/case_log_spec.rb
+++ b/spec/models/case_log_spec.rb
@@ -1070,9 +1070,14 @@ RSpec.describe Form, type: :model do
           relat3: "Child - includes young adult and grown-up",
           relat4: "Other",
           relat5: "Child - includes young adult and grown-up",
-          age4: 60,
+          relat7: "Other",
+          relat8: "Other",
+          age1: 22,
           age2: 14,
+          age4: 60,
           age6: 88,
+          age7: 16,
+          age8: 42,
         })
       end
 
@@ -1089,6 +1094,13 @@ RSpec.describe Form, type: :model do
         record_from_db = ActiveRecord::Base.connection.execute("select totelder from case_logs where id=#{household_case_log.id}").to_a[0]
         expect(record_from_db["totelder"]).to eq(2)
       end
+
+      it "correctly derives and saves totadult" do
+        household_case_log.reload
+
+        record_from_db = ActiveRecord::Base.connection.execute("select totadult from case_logs where id=#{household_case_log.id}").to_a[0]
+        expect(record_from_db["totadult"]).to eq(3)
+      end
     end
   end
 end