What a UK mobile number looks like and who assigns them

A UK mobile phone number has 11 digits and always starts with 07. The format is 07XXX XXXXXX, where X represents the remaining numbers. The first four digits after the 07 identify which network operator issued the number — for example, numbers starting 07911 typically belong to Vodafone, while 07700 numbers are often from O2. However, since phone numbers can be transferred between networks, the prefix is no longer a reliable way to identify which company currently owns the number.

The Office of Communications, known as Ofcom, is the UK regulator that oversees mobile numbering. Ofcom allocates blocks of numbers to the major network operators — Vodafone, O2, EE, and Three — who then issue them to customers. When you sign up for a mobile contract or pay-as-you-go service, the network assigns you a unique number from their allocated range.

Unlike landline numbers, which are tied to a physical address, mobile numbers are portable. You can switch networks and keep the same number through a process called number porting, which takes a few working days to complete. This means the 07 prefix tells you it is a mobile number, but not necessarily which network currently services it.

Key Takeaways

  • UK mobile numbers have 11 digits starting with 07, followed by a four-digit network identifier and six personal digits.
  • Ofcom allocates number blocks to the four major networks — Vodafone, O2, EE, and Three — but numbers can move between networks through porting.
  • The first four digits after 07 historically indicated the network operator, but this is no longer reliable since numbers can be transferred.
  • Mobile numbers are not tied to a location the way landline numbers are, so a 07 number can be used anywhere in the UK.
  • International callers can reach a UK mobile by dialling +44 7 followed by the remaining nine digits, dropping the leading 0.

How the number structure breaks down

The 11-digit structure divides into three parts. The first digit is always 0, which is the trunk prefix used for all UK domestic calls. The second digit is always 7, which designates the number as mobile rather than landline. Together, 07 tells the phone system you are calling a mobile device.

The next four digits — positions three through six — are the network identifier. Ofcom assigns these in blocks to each operator. Common prefixes include 07911–07919 for Vodafone, 07700–07709 for O2, 07953–07973 for EE, and 07797–07807 for Three. However, because number porting is common, you cannot assume a number belongs to a particular network based on these digits alone.

The final six digits are unique to the individual subscriber. These are assigned sequentially within each network's allocated blocks. Together, the four-digit prefix and six-digit suffix create a number that is unique across the entire UK mobile system.

How to identify whether a number is mobile or landline

The second digit is the key. If it is 7, the number is mobile. If it is 1, 2, 3, or 4, the number is a landline. Landline numbers also have 11 digits but follow the format 01XXX XXXXXX or 02X XXXX XXXX, depending on the region. The first digits after the initial 0 indicate the geographic area — for example, 0121 is Birmingham, 0161 is Manchester, and 020 is London.

Other non-geographic numbers exist for businesses and services. Numbers starting 03 are non-geographic landlines that can be reached from anywhere in the UK at the same rate as a local call. Numbers starting 08 are typically premium-rate or business services, and 09 numbers are high-cost services. Only 07 numbers are mobile.

What happens when you port a number to a different network

Number porting allows you to keep your existing mobile number when you switch networks. You request the port through your new network provider, who contacts your old provider to authorise the transfer. The old provider must comply within two working days. During this time, calls and texts may be unreliable, so most people complete the switch outside working hours or on a Friday to minimise disruption.

Once the port completes, your number routes to your new network's infrastructure, but the number itself does not change. Your contacts see the same 07 number, and they have no way of knowing you have switched providers. This is why the network prefix is no longer a reliable indicator of which company owns the number.

If you are trying to contact someone and need to know which network they are on — for example, to check roaming charges or network-specific rates — you cannot determine this from the number alone. You would need to ask them directly or check your call records with your own provider.

International dialling to a UK mobile number

To call a UK mobile from outside the country, replace the leading 0 with +44, which is the UK country code. A UK number 07911 123456 becomes +44 7911 123456 when dialled internationally. The +44 tells the international phone system to route the call to the UK, and the 7 identifies it as a mobile number within the UK network.

When you receive a call from abroad on your UK mobile, it appears on your phone as an incoming call from a +44 number. If you are abroad and want to call another UK mobile, you must use the +44 format; using the domestic 07 format will not work outside the UK.

Why UK mobile numbers are always 11 digits

The 11-digit length was set by Ofcom to provide enough unique numbers for the UK market while keeping numbers short enough to remember and dial easily. With 11 digits and the first two fixed as 07, there are theoretically 100 million possible mobile numbers (10 to the power of 9). In practice, Ofcom allocates numbers in blocks to each network, and networks manage their own inventory, so the actual number of active mobile numbers is lower.

As the UK mobile market has grown, Ofcom has had to manage number allocation carefully to avoid running out. In 2020, Ofcom began requiring networks to use numbers more efficiently and to return unused blocks. This ensures the supply of available numbers remains adequate for new customers and new networks entering the market.

Frequently Asked Questions

Can I tell which network a 07 number belongs to by looking at the digits?

Not reliably. While certain prefixes historically belonged to specific networks — 07911 to Vodafone, 07700 to O2, and so on — number porting means a number can move to a different network while keeping the same digits. The only way to know for certain is to ask the person or check your own provider's records.

What is the difference between a 07 number and a 03 number?

A 07 number is mobile and belongs to a person with a mobile device. A 03 number is a non-geographic landline, usually used by businesses or services, and can be reached from anywhere in the UK at standard landline rates. Both have 11 digits, but 03 numbers are not mobile phones.

Do I need to use +44 when texting a UK mobile from abroad?

Most modern phones automatically handle the format, but it is safest to use +44 7 followed by the remaining nine digits. Some older systems or international messaging services may not recognise the domestic 07 format when sent from outside the UK.

Can a UK mobile number be used outside the UK?

Yes. Your UK mobile number stays the same whether you are in the UK or abroad. When you travel, your phone connects to local networks through roaming agreements, but your number does not change. Incoming calls and texts still reach you at your 07 number, though roaming charges may explore depending on your contract.

How many UK mobile numbers are there in total?

Ofcom allocates numbers in blocks to each network operator. With 11 digits and the first two fixed as 07, there is theoretical capacity for 100 million numbers. The actual number of active mobile numbers in use is lower and varies month to month as customers sign up and leave.