diff --git a/BFR/MainWindow.xaml b/BFR/MainWindow.xaml
index b5e5193..cd35980 100644
--- a/BFR/MainWindow.xaml
+++ b/BFR/MainWindow.xaml
@@ -230,5 +230,35 @@
         </Grid>
       </Expander>
     </DataTemplate>
+    <DataTemplate DataType="{x:Type ops:Number}">
+      <Expander Classes="OperationExpander">
+        <Grid ColumnDefinitions="auto,*" RowDefinitions="auto,auto,auto,auto,auto,auto,auto,auto,auto">
+          <TextBlock Grid.Row="0" Text="Mode:"/>
+          <ComboBox Grid.Row="0" Items="{Binding Modes}" Name="ModeSelector" SelectedIndex="{Binding Mode}" PropertyChanged="PreviewChanged">
+            <ComboBox.ItemTemplate>
+              <DataTemplate>
+                <TextBlock Text="{Binding Name}"/>
+              </DataTemplate>
+            </ComboBox.ItemTemplate>
+          </ComboBox>
+          <TextBlock Grid.Row="1" Text="Pattern:" IsVisible="{Binding #ModeSelector.SelectedItem.IsReplace}"/>
+          <TextBox Grid.Row="1" Text="{Binding Pattern}" IsVisible="{Binding #ModeSelector.SelectedItem.IsReplace}" PropertyChanged="PreviewChanged"/>
+          <TextBlock Grid.Row="2" Text="Position:" IsVisible="{Binding #ModeSelector.SelectedItem.IsInsert}"/>
+          <NumericUpDown Grid.Row="2" Value="{Binding InsertPosition}" IsVisible="{Binding #ModeSelector.SelectedItem.IsInsert}" PropertyChanged="PreviewChanged"/>
+          <TextBlock Grid.Row="3" Text="Start Index:"/>
+          <NumericUpDown Grid.Row="3" Value="{Binding StartIndex}" PropertyChanged="PreviewChanged"/>
+          <TextBlock Grid.Row="4" Text="Increment:"/>
+          <NumericUpDown Grid.Row="4" Value="{Binding Increment}" PropertyChanged="PreviewChanged"/>
+          <TextBlock Grid.Row="5" Text="Padding:"/>
+          <NumericUpDown Grid.Row="5" Value="{Binding Padding}" PropertyChanged="PreviewChanged"/>
+          <TextBlock Grid.Row="6" Text="Auto Padding:"/>
+          <CheckBox Grid.Row="6" IsChecked="{Binding AutoPadding}" PropertyChanged="PreviewChanged"/>
+          <TextBlock Grid.Row="7" Text="Regex:" IsVisible="{Binding #ModeSelector.SelectedItem.IsReplace}"/>
+          <CheckBox Grid.Row="7" IsChecked="{Binding UseRegex}" IsVisible="{Binding #ModeSelector.SelectedItem.IsReplace}" PropertyChanged="PreviewChanged"/>
+          <TextBlock Grid.Row="8" Text="Full Name:" IsVisible="{Binding #ModeSelector.SelectedItem.IsReplace}"/>
+          <CheckBox Grid.Row="8" IsChecked="{Binding FullName}" IsVisible="{Binding #ModeSelector.SelectedItem.IsReplace}" PropertyChanged="PreviewChanged"/>
+        </Grid>
+      </Expander>
+    </DataTemplate>
   </Window.DataTemplates>
 </Window>
diff --git a/BFR/MainWindowUIProperties.cs b/BFR/MainWindowUIProperties.cs
index 4dd69f3..7ae2a2a 100644
--- a/BFR/MainWindowUIProperties.cs
+++ b/BFR/MainWindowUIProperties.cs
@@ -1,8 +1,8 @@
 using System.Collections.Generic;
 
 using Avalonia;
-using Avalonia.Collections;
 using Avalonia.Controls;
+using Avalonia.Collections;
 
 using BFR.DataModels;
 using BFR.Operations;
@@ -26,6 +26,7 @@ namespace BFR
             OperationType.Make<Overwrite>(),
             OperationType.Make<Replace>(),
             OperationType.Make<Remove>(),
+            OperationType.Make<Number>(),
         };
 
         public static readonly AvaloniaProperty<bool> IsCommitButtonEnabledProperty =
diff --git a/BFR/Operations/Number.cs b/BFR/Operations/Number.cs
new file mode 100644
index 0000000..ca477f7
--- /dev/null
+++ b/BFR/Operations/Number.cs
@@ -0,0 +1,69 @@
+using System.Xml.Serialization;
+using System.Collections.Generic;
+
+using Avalonia;
+
+using BFR.Helpers;
+using BFR.DataModels;
+
+namespace BFR.Operations
+{
+    public class Number : Operation
+    {
+        public override string Name => nameof(Number);
+        public override string Description => "Numbers all file names according to how they are sorted.";
+
+        public static readonly AvaloniaProperty<NumberMode> ModeProperty = 
+            AvaloniaProperty.Register<MainWindow, NumberMode>(nameof(Mode), NumberMode.Prefix);
+        public NumberMode Mode { get => GetValue(ModeProperty); set => SetValue(ModeProperty, value); }
+
+        [XmlIgnore]
+        public NumberOperationMode[] Modes => NumberOperationMode.Modes;
+
+        public int InsertPosition { get; set; } = 0;
+        public int Increment { get; set; } = 1;
+        public int StartIndex { get; set; } = 1;
+        public int Padding { get; set; } = 0;
+        public bool AutoPadding { get; set; } = false;
+        public bool FullName { get; set; } = false;
+        public bool UseRegex { get; set; } = false;
+        public string Pattern { get; set; } = "";
+
+        protected override void ApplyToInternal(IList<FileModel> files)
+        {
+            var index = StartIndex;
+            var padding = AutoPadding
+                ? (StartIndex + Increment * (files.Count - 1)).ToString().Length
+                : Padding;
+
+            foreach (var file in files)
+            {
+                var newName = FullName ? file.FullName : file.Name;
+                var text = PadInteger(index, padding);
+
+                newName = Mode switch
+                {
+                    NumberMode.Prefix => $"{text}{newName}",
+                    NumberMode.Suffix => $"{newName}{text}",
+                    NumberMode.Insert => newName.Insert(InsertPosition, text),
+                    NumberMode.Replace => newName.Replace(Pattern, text, UseRegex, false),
+                    _ => newName
+                };
+
+                if (FullName) file.FullName = newName;
+                else file.Name = newName;
+
+                index += Increment;
+            }
+        }
+
+        private static string PadInteger(int value, int padding)
+        {
+            var valueString = value.ToString();
+            while (valueString.Length < padding)
+                valueString = $"0{valueString}";
+
+            return valueString;
+        }
+    }
+}
diff --git a/BFR/Operations/NumberMode.cs b/BFR/Operations/NumberMode.cs
new file mode 100644
index 0000000..be20beb
--- /dev/null
+++ b/BFR/Operations/NumberMode.cs
@@ -0,0 +1,40 @@
+using System;
+using System.Linq;
+using System.Collections.Generic;
+
+using BFR.Helpers;
+
+namespace BFR.Operations
+{
+    public class NumberOperationMode : OperationMode<NumberMode>
+    {
+        public bool IsPrefix => Index == NumberMode.Prefix;
+        public bool IsSuffix => Index == NumberMode.Suffix;
+        public bool IsInsert => Index == NumberMode.Insert;
+        public bool IsReplace => Index == NumberMode.Replace;
+
+        public readonly static NumberOperationMode[] Modes = All();
+
+        public NumberOperationMode(NumberMode index, string name, string description) :
+            base(index, name, description) { }
+
+        protected static NumberOperationMode[] All() => ((IEnumerable<NumberMode>)Enum.GetValues(typeof(NumberMode))).Select(x =>
+            new NumberOperationMode(
+                x,
+                x.GetAttribute<OperationModeAttribute>().DisplayName,
+                x.GetAttribute<OperationModeAttribute>().Description
+            )).ToArray();
+    }
+
+    public enum NumberMode
+    {
+        [OperationMode(nameof(Prefix), "Inserts the numbering before the file name.")]
+        Prefix,
+        [OperationMode(nameof(Suffix), "Inserts the numbering after the file name.")]
+        Suffix,
+        [OperationMode(nameof(Insert), "Inserts the numbering at the specified index.")]
+        Insert,
+        [OperationMode(nameof(Replace), "Replaces the given pattern with the numbering.")]
+        Replace,
+    }
+}