A US phone number has three parts and a handful of accepted ways to write it. Which one you use depends on who reads it: a US customer, a client abroad, or a web form that stores it. Here is the structure, the formats, and how to write the number on a website, a business card, an email signature, an invoice and in forms. Every number in this article uses the 555-01xx range, which is set aside for examples.
What are the parts of a US phone number?
| Part | Example | What it is |
|---|---|---|
| Country code | +1 | The code for the North American Numbering Plan, shared by the US, Canada and several Caribbean countries |
| Area code | 212 | Three digits tied to a place, here Manhattan |
| Exchange | 555 | The first three digits of the local number |
| Line number | 0123 | The last four digits |
So every US number is +1 followed by exactly 10 digits. The area code and the exchange never start with 0 or 1, under the numbering plan that NANPA administers. If you see a 0 or a 1 right after +1, the number is written wrong.
The ITU’s E.164 recommendation is the international standard behind all of this: a country code, then the national number, up to 15 digits in total.
Which format should you use?
| Format | Example | Best for |
|---|---|---|
| International, with spaces | +1 212 555 0123 | Readers outside the US, business cards, international clients |
| International, US style | +1 (212) 555-0123 | Sites read in the US and abroad |
| US national | (212) 555-0123 | US readers only |
| US with dashes | 212-555-0123 | US readers, compact layouts |
| E.164 | +12125550123 | Forms, databases, CRMs, tel: links, apps |
| US long-distance habit | 1-212-555-0123 | US readers; confusing abroad, so avoid it |
All of these are the same number. The mistake is mixing them. Pick one style for everything people read, and use E.164 for everything a machine reads.
If your callers are spread across countries, the international style is the safe choice. A US caller still recognizes the area code, and a caller in London or Dubai sees the +1 they need to dial.
How do you write it on a website?
Put it as text, not inside an image, so phones can tap it, screen readers can read it and search engines can see it. Then add what callers need to know:
- A label, such as “US phone” or “Call our US line”.
- Your hours in a US time zone, such as “Mon–Fri, 9 a.m.–1 p.m. Eastern”. Say “Eastern” or “Pacific” rather than EST or PST, so it stays right all year.
- A written channel, such as an email address or a contact form.
A made-up example of a contact block:
US phone: +1 212 555 0123 (Mon–Fri, 9 a.m.–1 p.m. Eastern). Leave a voicemail outside these hours and we call back the next working day. For written questions, email [email protected].
The business contact checklist covers the rest of the contact page.
How do you make a click-to-call link?
Use a tel: link. The visible text can use any format you like, but the link itself should be E.164: a plus sign, the country code and the 10 digits.
<a href="tel:+12125550123">+1 212 555 0123</a>In Markdown, the same link is:
[+1 212 555 0123](tel:+12125550123)Three rules keep it working:
- Start with
tel:+1. Without the country code, a visitor abroad dials a local number in their own country. - No spaces in the link. The tel URI standard allows dashes and dots as separators, but spaces are not part of it. The plain form is the safest.
- Test it. Tap it on an iPhone and an Android phone. On a computer, the link may open a calling app or ask which app to use.
How do you write it on a business card, signature and invoice?
| Where | How to write it | Add |
|---|---|---|
| Business card | +1 212 555 0123 | “US” as a label, and your email |
| Email signature | +1 212 555 0123, linked with tel:+12125550123 in an HTML signature | Your hours and time zone |
| Invoice | +1 212 555 0123 | A billing email, so payment questions arrive in writing |
| Social profiles | +1 212 555 0123 | The same hours as your website |
Use the same style everywhere. A customer who sees +1 212 555 0123 on your card and 212.555.0123 on your invoice may wonder whether they are the same number.
How do you enter a US number in a form that asks for your country?
- Choose United States (+1) from the country list. Canada also uses +1, so pick the right country rather than the first +1 in the list.
- Type the 10 digits only: 2125550123. Do not add +1, a leading 1 or a 0. The form adds the country code itself.
- If there is no country list, type the full number as +12125550123.
- If the form rejects the plus sign, try 12125550123, or ask the site which format it wants.
Apps such as WhatsApp work the same way: choose the country, then enter the 10 digits.
How does someone abroad dial a US number?
They dial their own exit code, then 1, then the 10 digits. From the UK, India or the UAE that is 00 1 212 555 0123. On a mobile, +1 212 555 0123 works from any country, which is why the international format is the one to publish. Our guide on how to call the US from abroad has exit codes for 17 countries, and the dialing tool builds the full number for you.
Why do examples use 555-0100 to 555-0199?
NANPA sets aside 555-0100 through 555-0199 for fictional use, in films, books, ads and sample text. Using them in templates, screenshots and test data means nobody real gets a call from someone copying your example. Other 555 numbers can be in real use, so stay inside the 01xx range.
What mistakes should you avoid?
- Writing 001 or 011 in front. Exit codes differ by country, so the plus sign is the only prefix that works for everyone.
- Adding (0). US numbers have no trunk zero: +1 (0)212 is wrong.
- Dropping the area code. From abroad, all 10 digits are needed.
- Too many digits. After +1 come exactly 10 digits.
- A number only in an image. It cannot be tapped, copied or read aloud by a screen reader.
What does this mean for a TripoSIM number?
A TripoSIM US Virtual Number is a +1 number with the area code you choose by state or area code, so all of the rules above apply. A few things to say next to it on your site:
- “Call or email”, not “call or text”. The number receives texts from US and Canadian senders, but sending texts is not included.
- Your hours. Calls ring in the TripoSIM app over Wi-Fi or mobile data; outside your hours, callers can leave a voicemail.
- Nothing about emergencies. It cannot call 911 or any emergency service.
The bottom line
Write a US number as +1 and 10 digits. Use +1 212 555 0123 for mixed or international readers, (212) 555-0123 for US readers, and +12125550123 in forms and tel: links. Keep one style everywhere, add your hours in a US time zone, and use 555-01xx numbers in examples. To choose an area code your callers recognize, see the area code guide, and compare both plans on the plans page.