diff --git a/app/models/transaction.rb b/app/models/transaction.rb
index 1e48af6..6dd1bbb 100644
--- a/app/models/transaction.rb
+++ b/app/models/transaction.rb
@@ -16,7 +16,16 @@ class Transaction < ActiveRecord::Base
   belongs_to :debtor, class_name: 'User'
   belongs_to :creditor, class_name: 'User'
 
+  after_save    :recalculate_balances
+  after_destroy :recalculate_balances
+
   def client
     Client.find_by name: origin
   end
+
+  private
+  def recalculate_balances
+    creditor.calculate_balance!
+    debtor.calculate_balance!
+  end
 end
diff --git a/app/models/user.rb b/app/models/user.rb
index 85881b5..18f7582 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -21,6 +21,12 @@ class User < ActiveRecord::Base
     Transaction.where("creditor_id = ? OR debtor_id = ?", id, id)
   end
 
+  def calculate_balance!
+    balance = incoming_transactions.sum(:amount) -
+                outgoing_transactions.sum(:amount)
+    self.update_attribute :balance, balance
+  end
+
   def self.from_omniauth(auth)
     where(name: auth.uid).first_or_create do |user|
       user.name = auth.uid