🇬🇧 United Kingdom Phone Number Format

United Kingdom numbers are administered by Ofcom and are typically 10 digits after the leading trunk 0 (11 digits total in national format). Mobiles start with 07, London landlines with 020 — and the moment you go international, that leading 0 disappears behind +44.

The Same UK Number in Every Standard

Here is how one United Kingdom number is written in each of the four standards:

FormatExampleUse for
E.164 +447400123456 Databases, SMS APIs (Twilio, WhatsApp), CRMs
International +44 7400 123456 Display to a global audience, business cards
National 07400 123456 Domestic display inside United Kingdom
RFC3966 tel:+44-7400-123456 Clickable tel: links on websites

Ofcom, the Big Number Change and Drama Numbers

Modern UK numbering dates from the “Big Number Change” of 2000, when London consolidated onto the 020 code and mobiles standardised on 07. The result is a tidy split: 01/02 geographic, 03 non-geographic at local rate, 07 mobile, 08 freephone and special rates — the first two digits tell you what you’re paying before you dial.

Ofcom publishes ranges reserved purely for fiction — film and TV use 020 7946 0xxx for London and 07700 900xxx for mobiles so no real subscriber gets nuisance calls. A subtlety that trips up developers: strict validators built on Google’s libphonenumber reject the 07700 900xxx drama mobiles as unallocated, while the 020 7946 drama landlines pass. Test data that “looks British” can therefore fail real validation.

Watch out for 070 numbers: they read like mobiles but are “personal numbering” services that can cost several pounds per minute, which is why many fraud filters block them outright.

UK Mobile Prefixes (07) and Geographic Area Codes

TypePrefixesDigitsExample
Mobile 071–075, 077–079 11 (incl. leading 0) 07400 123456
London landline 020 11 020 7946 0958
Other geographic 01, 02 10–11 0117 496 0123
Freephone 0800, 0808 10–11 0800 496 0123
Non-geographic 03 11 0306 999 0123

Calling the UK: Drop the Zero After +44

Calling fromDial
Within the UK 07400 123456 — Keep the leading 0 domestically.
From the US 011 44 7400 123456 — Drop the leading 0 after +44.
From any mobile +44 7400 123456
  1. Enter + or your country’s international prefix.
  2. Add the UK country code 44.
  3. Drop the leading 0 from the UK number.
  4. Dial the remaining digits, e.g. 7400 123456.

UK Number Traps: Drama Ranges and 070 Lookalikes

  • The single most common mistake with UK numbers is keeping the leading 0 after +44 — “+44 07400…” is always wrong.
  • Ofcom reserves drama ranges like 020 7946 0000–0999 for fictional use — but note that strict validators built on Google’s libphonenumber reject the reserved mobile drama range 07700 900xxx as unallocated.
  • UK mobile numbers are always 11 digits nationally (07 + 9 digits); London numbers are 020 + 8 digits.
  • 070 numbers look like mobiles but are “personal numbering” services billed at premium rates — many spam filters block them.

Common UK Formatting Mistakes

  • Keeping the trunk zero after the country code — “+44 07400 123456” is never correct; the 0 must go.
  • Writing “+44 (0)20 7946 0958” — the parenthetical zero confuses auto-diallers and CRMs; pick one form.
  • Treating 070 numbers as mobiles — they are premium personal-numbering services, not handsets.
  • Storing numbers with inconsistent spacing (07400123456 vs 07400 123 456) — normalise to E.164 +447400123456 instead.

Convert a UK Number Now

Type a UK mobile or landline in any style — 07…, +44, even with the stray (0) — and get the correct E.164 and international forms instantly.

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UK Phone Format: Your Questions Answered

How do I write a UK mobile number in international format?

Replace the leading 0 with +44. So 07400 123456 becomes +44 7400 123456, or +447400123456 in strict E.164 for APIs and contact databases.

Do I keep the 0 after +44?

No. The leading 0 is the UK national trunk prefix and is always dropped in international format. +44 07400 123456 is invalid; the correct form is +44 7400 123456.

How many digits does a UK phone number have?

Most UK numbers are 11 digits including the leading 0 (10 significant digits after it). A few older geographic areas still use 10-digit numbers.

What do UK mobile numbers start with?

UK mobiles start with 07 — specifically 071–075 and 077–079. Note that 070 numbers are not real mobiles but premium “personal numbers”.

How do I call a UK number from the US?

Dial 011 (US exit code), then 44, then the UK number without its leading 0: 011 44 7400 123456. From a mobile, +44 7400 123456 works directly.

Other Country Formats