How to Add Extension to Phone Number?

  • Last Updated: 10 Apr 24
  • 14 min read

Phone number extensions have been an important aspect of telephony for a very long time. This feature is almost as old as the landline telephone technology. However, not many people have a clear understanding of the phone number extension.🤔 

Once your business grows, phone system requirements elevate along with it. That means more employeesmore phone numbers

How will your business manage when your employees cross thousands? 

Here, comes phone extension numbers to streamline your business communications. It helps you save money, and more importantly, deliver exceptional customer experience. 

But, how can this be achieved? 

Through this article, we aim to explore and understand every minute detail about phone number extension and, most importantly, learn how to add extension to a phone number

🗝️ Key Highlights

  • A phone number extension consists of 3 to 5 digits that can be manually assigned to individual team members, teams, divisions, or entire departments within your business.
  • Call routing to extensions involves dialing the number with or without the extension, entering a queue if necessary, and connecting to the desired extension.
  • To add extension from the company’s perspective, use the administrator panel to assign 3 to 5-digit numbers to subdivide the main line. For customers, adding extensions on Android and iOS involves accessing phone settings to include additional digits after the main number.
  • Residential extensions connect multiple phones to one line, limiting to one call at a time and potential privacy issues. Business extensions subdivide main lines for multiple simultaneous calls, offering cost-saving and efficient communication.

Let us start from the basics.😊

What is a phone number extension?

A phone number extension is a combination of 3 to 5 digits that you can manually assign to any of your team members, a team, a division, or the whole department of your business. Extensions are sub-divisions of the main line

Confused? Don’t worry; we shall elaborate on this with examples. 

For example, your company has a phone number that reads as 987 654321. Now, you decide to assign extensions 200 to the sales department and 300 to customer support. 

There arise two scenarios with this, one being the internal callers and external callers, the other. Internal callers (indicating departments or employees within the company) can simply dial 200 to contact the sales and 300 to reach the marketing department. 

Whereas, external callers (indicating customers and parties outside the company) should dial 987654321,200 to directly reach the sales department and 987654321, 300 to reach customer support. 

Phone number extension format: actual phone number, dedicated extension

Phone number extension example: +1 1424622, 231

Here, +1 1424622 is the actual phone number of a company, a comma to indicate the initiation of an extension, and 231 is the dedicated extension. 

A phone number extension facilitates callers to quickly and effortlessly reach the target personnel or the department without having to deal with auto attendants. Employees and teams within the company can simply dial extensions to reach out to each other. 

The very reason why it is also termed extension dialing.

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How are calls routed to an extension number?

Call routing to an extension depends on and varies from one service provider to another. However, all of them use the basic call routing architecture, which can be summed up in three main points.

Steps for Calls routed to an extension number:

How are calls routed to an

Step 1: A caller dials

When callers dial the phone number with an extension number saved on their cell phone, callers automatically dial extensions. There is a possibility that the call bypasses an IVR or an auto attendant.

However, if a caller dials the phone number without an extension, saved on their contacts app, the call cannot bypass the auto attendant. 

In both cases, the caller has reached so far only the main line, it is where the routing mechanisms (a specific set of coding or hardware) comes into action. 

Step 2: Call router in action

Based on the extension chosen or dialed by the caller, the automated system (software) routes the calls to their dedicated destinations. If there are a lot of callers on the line, it queues the caller and informs them about their position on the line. 

The router is where different service providers vary from one another. However, the basic principle remains the same – identify extensions and route calls to dedicated extensions. 

Once the queue is over, the line or call is connected to the target line or extension. 

Step 3: Caller gets connected to the target extension

The final step is where the caller reaches his/her target destination, whether it be an employee, customer support, sales department, or something else. 

Extension call routing is down to a set of coding and a small piece of hardware that recognizes and establishes connections based on the dial extensions. 

Benefits of using phone number extensions

Phone number extensions come with an unlimited number of benefits, especially with VoIP services. 

From streamlining your business communications to helping you save a fortune on communications,  in the long run. 


Some noteworthy benefits of using phone number extensions are bulleted below:

  • Saving money: A single main line can facilitate multiple extensions, which means you do not spend for individual numbers, saving your business money. 
  • Streamline calling:  Facilitates employees to communicate with each other by simply dialing dedicated phone extension – need not remember the whole phone number.
  • Enable employee mobility: Extensions work similarly to VoIP services enabling your employees to be productive on the move. 
  • Customer-first experience: Let your customers know the extensions for all of your business departments, which enables them to bypass the auto-attendants creating a better customer experience.
  • Focus on hybrid work culture: Extensions enable your company to employ workers on both on-site and remote stations, providing synchronized communications on all ends to keep everyone on the same page. 
  • Focus on productivity and efficiency: Your employees can focus on more important aspects of the work, leaving strenuous and monotonous tasks to the IVRs. 
  • Easy to remember vanity numbers:  With virtual numbers, you can play around to create eye-catching vanity numbers and insert similar extensions at the end so that your audience remembers them forever. A unique way of marketing. 
  • Exceptional customer communication: Extensions enable your customers to reach their targeted destinations easily and effortlessly using the extensions, or with the help of IVR or auto-attendants. 
  • A clear overview of individual performances: You can easily track, record, and analyze the progress and effectiveness of your employees through their dedicated extensions.
👋 Take a look at: How to Share Business Phone Number With Your Team

How to add extension to a phone number?

Adding an extension to a phone number can mean two different things depending on the caller or customer and the company. 

From the company’s point of view, adding an extension to a phone number means literally assigning 3 to 5-digit numbers behind the main number to subdivide the main line.

This can be accomplished from the administrator panel. One thing you should remember is that different service providers have variable admin settings and panels so you may require a helping hand from customer support in the beginning. 

However, here we shall discuss how to add extension to a phone number from the customer’s POV

Adding an extension to a phone number on Android and iPhone or iOS has a similar step, not the same. 

So let us explore them separately, in the following sections:

How to add extension to iPhone contacts?

You can add extension to a phone number on iPhone contacts while creating a new contact or editing the existing contact. It allows you to automatically dial extensions the next time you make a call to that extension. 

Follow the steps to add extension to iPhone contacts.

(While creating or editing a contact on iPhone, the main thing you should focus on is the phone number)

Steps to add extension to iPhone contacts:

  • Open the contacts app on your iPhone and select the contact you want to add extension to,
  • Tap Edit and tap the contact’s phone number section,
  • Place your cursor at the end of the phone number
  • Tap the “+*#” button on the dial pad to access further options
  • Tap on the “wait” button and enter the extension
  • Tap “done” in the top-right corner.

To add a pause, you can add a comma (,) instead of a semicolon (;). A comma indicates a pause instead of a wait. The phone number in your iPhone contact will appear as +1 1424622;123 after you perform the above steps. (+1 1424622 being your contact phone number)

😍You may also like: How To Auto-Reply Text On iPhone

How to add extension to a phone number on android?

Adding an extension to a phone number on an Android device is similar to that of an iPhone. Let us learn how to add extension to a phone number in an existing contact on an Android phone. 

Steps to add extension to a phone number on android:

  • Open the contacts app or go to the phone app and tap on contacts, 
  • Select open the contact you want to edit,
  • Tap on the pencil icon or edit button,
  • Tap on the contact’s phone number section and place your cursor at the end of the number,
  • Enter a single comma (,) for a two second pause or add a semicolon (;) for a wait,
  • Enter an extension and tap on save. 

Important note: Tap pause or a comma (,) if you can enter the extension as soon as the call is answered. If you have to wait a bit longer to let the automated message complete, use the wait method, a semicolon (;).

You simply dial the extension number to make a call to the next employee or the department. For example, if Ken is assigned a 123 extension and you want to contact him from within the company, just dial 123, tap the green phone button, and you will ring his cell phone. 

Business Vs. Residential Phone Number Extension

Most people have a blurred understanding of extension numbers, and they tend to generalize their functionality to business and residential phone numbers. However, you should know that these two are separate in nature

Let us explore them in the following sections and find out how they differ. Residential phone number extension doesn’t necessarily include a sub-division of the main line. The main line itself is connected to multiple phone systems (indicating answering machines), so for an inbound call, all the connected phones ring at the same time. You are allowed to answer the call from any one of those endpoints.

Residental Phone Number

The drawback of this extension is someone else can listen to your conversation and join in from the next endpoint. Also, only a single call is allowed at once. You cannot make or receive a second call concurrently.

However, it is not the same case with business phone number extensions. It allows your business to subdivide the main line into multiple lines using different extension numbers. The main line is used to connect a caller to an extension, and it becomes partially free, which allows a second and a third concurrent call dedicated to a sub-divided extension.

Business Phone Number

The excellent aspect of business phone number extension is that you can purchase three to four main lines/phone numbers and subdivide them into 9 to 10 sub-lines using different extensions. It saves your company money and facilitates better and quicker internal communications. 

👋 Take a look at: How to get a phone number for your personal or business use

Is a virtual phone number and extension the same? 

Let us make it clear that a virtual phone number and an extension aren’t the same things. Virtual phone numbers are a set of unique phone numbers that utilize internet connectivity to establish communication between callers. These numbers are the future of telephony and shall replace wired telephony soon. 

Whereas phone number extensions are simply a set of 3-5 digit numbers that are used to subdivide a phone number or a phone line into multiple lines. 

You could say that a virtual phone number is associated with an IP address, whereas an extension isn’t. An extension is used to divide any phone number into sub-numbers. Let us explain it with an example.

A virtual phone number example: +1 617-495-1000 (the main virtual phone number of a college)

Phone number of the Science Department: +1 617-495-1000, 111 (111 – extension used for the Science Department)

Phone number of the Management Department: +1 617-495-1000, 222 (222- extension used for Management Department)

Here, the main phone number has been divided into two sub-numbers to connect to different departments. A virtual number acts as the main line, and the extension helps to create sub-lines.

👋 Take a look at: Direct-Dial-In Numbers: Everything You Need to Know


Now you have a comprehensive understanding of phone number extensions, I assume you sure know how to add extension to a phone number. As a customer or a caller, the information in this article is adequate for you to add and automatically dial extensions. 

However, as a business, you should also understand that phone service providers are also important in the equation. The service providers determine the number of extensions per phone number, communication features, product pricing, customer service, and the quality of service as well. 

With the right service provider, such as KrispCall, you can optimize your business communication system for seamless operation and enhance customer satisfaction. KrispCall offers 24/7 human customer support and advanced features, making it a valuable option for high-quality phone extensions.

👉 Reach out to the sales team and understand it in depth.


What does an extension mean in a phone number?

An extension means the division of the main phone number into multiple sub-sections or numbers to facilitate multiple endpoints to communicate with each other. It is a simple concept to share a phone number with multiple team members or departments. 

+1 1424622 is the main phone number in a company
+1 1424622,123 can be a sub-number for the customer support department
+1 1424622,222 can be a sub-number for the sales department
And so on.

How do I find an extension of a phone number?

Your phone service providers offer you options for choosing an extension for your phone numbers. It totally depends upon the service providers and how many extensions you get per phone number. 

How can I see the phone number extension for an incoming call on my phone (iPhone & Android)? 

You cannot see the phone number extensions for an incoming call on your cell phone either iPhone or Android phone. When a person with an extension number calls you, the call is processed via the main number, which is only displayed on your phone app – extension numbers aren’t displayed.

How do phone extensions work?

Phone extensions work by dialing an extension number from the main phone number, where it will route the call to a designated person, and the receiver will receive the call.

How can I add an extension to a phone number on a desk phone?

On most desk phones, you can manually enter the main phone number followed by the extension number using the pause key or extension symbols.

Can I add an extension to a phone number on an automated phone system?

Yes, when navigating through automated phone systems, you can usually enter the main phone number followed by the extension once connected.

Is there a way to add an extension for immediate dialing on a mobile phone?

Yes, on your mobile phone’s contacts, you can save the main phone number along with the extension, allowing for immediate dialing.

Can I add multiple extensions for speed dialing on a desk phone?

Yes, many desk phone and mobile phone support speed dial function where you can assign a speed dial number to a phone number with an extension.

Arun Chaudhary

Arun is SEO Analyst at KrispCall. He has written in extensively in the field of cloud telephony and call center solutions.

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