United States phone number format
Country code +1, 10 digits after it. Below is the same example written every way you are likely to need it.
Example mobile number
This is a numbering-plan example, not a real subscriber’s line. It is generated from the same data the validator uses, so it always matches what the API accepts.
Check a real United States number
Formatting is the easy half. The validator reports whether the number is actually allocated, its line type, and a risk score — free, no signup.
Open the free phone validator →From your code
curl "https://www.layercall.com/v1/lookup/phone?phone=%2B12015550123" \
-H "X-Api-Key: YOUR_KEY"1,000 lookups a month free, no card. Get an API key.
Questions
What is the country code for United States?
United States's country calling code is +1. In E.164 — the format almost every API, SMS gateway and CRM expects — it is written with no spaces, brackets or dashes, like +12015550123.
How many digits is a United States phone number?
10 digits after the +1 country code. Written nationally it may show no trunk prefix.
Does the leading 0 get included when dialling United States from abroad?
United States numbers do not use a national trunk prefix, so the national and international digits are the same after the +1 country code.
Is a correctly formatted number the same as a real one?
No, and conflating the two is the usual mistake. Formatting only says a number could exist. It does not say whether the range was ever allocated, whether it is mobile, fixed line or VoIP, or whether it is worth trusting on a signup — those need a lookup against numbering-plan data.