diff --git a/davtelepot/__init__.py b/davtelepot/__init__.py
index a810614..e8059b4 100644
--- a/davtelepot/__init__.py
+++ b/davtelepot/__init__.py
@@ -11,10 +11,12 @@ __author__ = "Davide Testa"
 __email__ = "davide@davte.it"
 __credits__ = ["Marco Origlia", "Nick Lee @Nickoala"]
 __license__ = "GNU General Public License v3.0"
-__version__ = "2.5.12"
+__version__ = "2.5.13"
 __maintainer__ = "Davide Testa"
 __contact__ = "t.me/davte"
 
-from . import administration_tools, authorization, bot, helper, languages, suggestions, utilities
+from . import (administration_tools, authorization, bot, helper, languages,
+               suggestions, useful_tools, utilities)
 
-__all__ = [administration_tools, authorization, bot, helper, languages, suggestions, utilities]
+__all__ = [administration_tools, authorization, bot, helper, languages,
+           suggestions, useful_tools, utilities]
diff --git a/davtelepot/messages.py b/davtelepot/messages.py
index 7121f2f..40a2e3f 100644
--- a/davtelepot/messages.py
+++ b/davtelepot/messages.py
@@ -1006,3 +1006,43 @@ default_unknown_command_message = {
     'en': "Unknown command! Touch /help to read the guide and available commands.",
     'it': "Comando sconosciuto! Fai /help per leggere la guida e i comandi."
 }
+
+default_useful_tools_messages = {
+    'length_command': {
+        'description': {
+            'en': "Use this command in reply to a message to get its length.",
+            'it': "Usa questo comando in risposta a un messaggio per sapere "
+                  "quanti caratteri contenga.",
+        },
+        'help_section': {
+            'description': {
+                'en': "Use the /length command in reply to a message to get "
+                      "its length.\n"
+                      "Beware that emojis may count as multiple characters.",
+                'it': "Usa il comando /caratteri in risposta a un messaggio "
+                      "per sapere quanti caratteri contenga.\n"
+                      "Attenzione alle emoji, che contano come più caratteri.",
+            },
+            'label': {
+                'en': "Length #️⃣",
+                'it': "Caratteri #️⃣"
+            },
+            'name': "length",
+        },
+        'instructions': {
+            'en': "Use this command in reply to a message to get its length.",
+            'it': "Usa questo comando in risposta a un messaggio per sapere "
+                  "quanti caratteri contenga.",
+        },
+        'language_labelled_commands': {
+            'en': "length",
+            'it': "caratteri",
+        },
+        'result': {
+            'en': "<i>According to my calculations, this message is "
+                  "</i><code>{n}</code><i> characters long.</i>",
+            'it': "<i>Questo messaggio contiene </i><code>{n}</code><i> "
+                  "caratteri secondo i miei calcoli.</i>",
+        },
+    },
+}
\ No newline at end of file
diff --git a/davtelepot/useful_tools.py b/davtelepot/useful_tools.py
new file mode 100644
index 0000000..82cc8e7
--- /dev/null
+++ b/davtelepot/useful_tools.py
@@ -0,0 +1,61 @@
+"""General purpose functions for Telegram bots."""
+
+# Standard library
+from collections import OrderedDict
+
+# Project modules
+from .bot import Bot
+from .messages import default_useful_tools_messages
+from .utilities import recursive_dictionary_update
+
+
+async def _length_command(bot: Bot, update: dict, user_record: OrderedDict):
+    if 'reply_to_message' not in update:
+        text = bot.get_message(
+            'useful_tools', 'length_command', 'instructions',
+            user_record=user_record, update=update
+        )
+    else:
+        text = bot.get_message(
+            'useful_tools', 'length_command', 'result',
+            user_record=user_record, update=update,
+            n=len(update['reply_to_message']['text'])
+        )
+        update = update['reply_to_message']
+    reply_to_message_id = update['message_id']
+    return dict(
+        chat_id=update['chat']['id'],
+        text=text,
+        parse_mode='HTML',
+        reply_to_message_id=reply_to_message_id
+    )
+
+
+def init(telegram_bot: Bot, useful_tools_messages=None):
+    """Define commands for `telegram_bot`.
+
+    You may provide customized `useful_tools_messages` that will overwrite
+        `default_useful_tools_messages`. Missing entries will be kept default.
+    """
+    if useful_tools_messages is None:
+        useful_tools_messages = dict()
+    useful_tools_messages = recursive_dictionary_update(
+        default_useful_tools_messages,
+        useful_tools_messages
+    )
+    telegram_bot.messages['useful_tools'] = useful_tools_messages
+
+    @telegram_bot.command(
+        command='/length',
+        aliases=None,
+        reply_keyboard_button=None,
+        show_in_keyboard=False,
+        **{
+            key: val
+            for key, val in useful_tools_messages['length_command'].items()
+            if key in ('description', 'help_section', 'language_labelled_commands')
+        },
+        authorization_level='everybody'
+    )
+    async def length_command(bot, update, user_record):
+        return await _length_command(bot=bot, update=update, user_record=user_record)
diff --git a/davtelepot/utilities.py b/davtelepot/utilities.py
index c554589..bd51cda 100644
--- a/davtelepot/utilities.py
+++ b/davtelepot/utilities.py
@@ -1682,3 +1682,21 @@ async def send_part_of_text_file(bot, chat_id, file_path, caption=None,
                 )
     except Exception as e:
         return e
+
+
+def recursive_dictionary_update(one: dict, other: dict) -> dict:
+    """Extension of `dict.update()` method.
+
+    For each key of `other`, if key is not in `one` or the values differ, set
+        `one[key]` to `other[key]`. If the value is a dict, apply this function
+        recursively.
+    """
+    for key, val in other.items():
+        if key not in one:
+            one[key] = val
+        elif one[key] != val:
+            if isinstance(val, dict):
+                one[key] = recursive_dictionary_update(one[key], val)
+            else:
+                one[key] = val
+    return one