United Kingdom · +44
UK phone number format
A UK number written for software is +44 followed by the national
number with the leading zero removed. 020 7183 8750 becomes
+442071838750. That one dropped zero is the single most common reason a UK
list fails an import, and it is the first thing to check.
The rule, in one line
020 7183 8750 → drop the 0 → +442071838750
The leading 0 is a trunk prefix: an instruction to the UK network
meaning "this is a national call", not part of the number. Keep it and you produce
+4402071838750, which is not a number anywhere.
scroll to see the whole number
+44 do the same job, so a number carries one
or the other and never both. Unlike the NANP, the prefix also tells you the line type before
any lookup: 07 is mobile, 01 and 02 are geographic.Why UK numbers are not all the same length
US numbers are always ten digits. UK numbers are not, and software written on the American assumption breaks on them. After the trunk zero is removed a UK national number is usually nine or ten digits, and which one depends on where it is:
020 xxxx xxxx
London. Two-digit area code, eight-digit local number — ten digits after the zero. Also 023, 024, 028 and 029 for Southampton/Portsmouth, Coventry, Northern Ireland and Cardiff.
0121 xxx xxxx
The big cities on three-digit codes — Birmingham, Edinburgh, Glasgow, Liverpool, Manchester, Sheffield, Leeds, Bristol, Nottingham. Ten digits after the zero.
01xxx xxxxxx
Most of the country, on four- and five-digit area codes. Usually ten digits after the zero, but a handful of areas still carry nine-digit numbers.
07xxx xxxxxx
Mobile. Always ten digits after the zero, so always +447 followed by nine
more.
A validator that hard-codes a length will reject real numbers. The only safe approach is to check the number against the published allocation ranges, which is what the numbering plan is for.
Mobile and landline are separate ranges, and that matters
This is where the UK is easier than the US. In the North American plan, mobile and landline
share the same number space, so the only way to tell them apart is to look up which carrier
holds the block. In the UK they come from entirely separate ranges: anything starting
07 is mobile, anything starting 01 or 02 is
geographic. The number itself tells you, before any lookup.
There is a visible consequence of that in the data. For +44 we hold 312,415 blocks, and they are distributed very unevenly:
landline270,717 blocks
non-geographic13,726 blocks
premium8,507 blocks
freephone7,928 blocks
mobile2,171 blocks
Mobile looks tiny next to landline, and it is not because there are fewer mobiles. It is because mobile ranges are allocated in a few very large chunks — most of our mobile entries are four or five digits deep — while geographic numbers are carved up far more finely, 214,042 of them at seven digits. Coarse blocks for mobile, fine blocks for landline. The same table, two completely different shapes.
What the prefix tells you before you dial
+447…
Mobile. +447911123456 returns mobile, carrier JT (Guernsey) Limited.
+4420…
London landline. +442071838750 returns landline, carrier AQL Wholesale.
+443…
Non-geographic, charged at geographic rates. +443003334444 returns
non-geographic, TalkTalk.
+448…
Freephone (0800, 0808) and business rate.
+449…
Premium rate. +449098790000 returns premium. These cost the caller
significantly more and are rarely what you want in a marketing list.
Every result above is a live response from the free lookup, checked today. The carrier is the one the block was allocated to; UK portability is heavy, especially on mobile, so a ported number will still report its original network.
The numbers that look fine and are not
Ofcom reserves 07700 900000 to 07700 900999 for drama — the
UK equivalent of 555-0100 in American film. Those numbers are used on television precisely
because they reach nobody.
Worth being straight about what our own engine does with one:
+447700900123 comes back valid, mobile. That is correct rather than a
bug — the range genuinely is allocated, for that purpose — and it is a good
illustration of the limit of allocation data. It can tell you a number is structurally
real and sits in an assigned block. It cannot tell you anyone will answer.
Converting a UK list
- Strip everything that is not a digit, keeping any leading
+. - If it starts
44and the next digit is0, remove that zero. - If it starts
0, replace the leading zero with+44. - If it starts
00, that is the UK international access code — replace the00with+and treat what follows as a country code. - Nine or ten digits should remain after
+44. Anything shorter is not a complete number, and padding it is inventing data.
The free browser cleaner does all five on a whole file, including the trunk-zero case, without the file leaving your machine.
Common questions
How do I write a UK phone number in international format?
Replace the leading 0 with +44. 07911 123456
becomes +447911123456, and 020 7183 8750 becomes
+442071838750. No spaces, no brackets.
Do I keep the 0 when adding +44?
No. The zero and the +44 do the same job, and keeping both produces a number
that does not exist. This is the single most common fault in UK phone data.
How many digits is a UK mobile number?
Eleven including the leading zero (07911 123456), or ten after it is removed.
In E.164 that is +44 plus ten digits, so thirteen characters including the
plus.
Is 07700 900123 a real number?
It is a real, allocated range, and it will not connect. Ofcom reserves
07700 900000–900999 for use in television and film. Allocation data
reports it as valid because it is assigned; that is the honest limit of what offline data
can tell you.
Can I tell a UK mobile from a landline without a lookup?
Yes, from the prefix: 07 is mobile, 01 and 02 are
geographic. That is a property of the UK numbering plan, and it is why line type is more
reliable here than in North America, where the two share the same ranges.
How line type is derived.