--- title: "United States (+1) Country Calling Code & SMS Numbering Plan" --- United States (+1) Country Calling Code & SMS Numbering Plan: SMSRiver - [Skip to main content](#main-content) [sms river .com](/) [Public Inboxes](/#numbers-section) [Country Codes](/country-codes/) [Workbench](/workbench/) [Tools](/tools/) [Developer API](/developer/) [Pricing](/pricing/) [Log In](/accounts/login/) [Log In](/accounts/login/) [Get API Key](/pricing/) [Home](/) - [Country Codes](/country-codes/) - United States (+1) National Telecom Specification # United States (+1) Country Calling Code & SMS Guide Complete engineering reference for phone numbering formats, domestic trunk prefixes, cellular mobile operator allocations, and regulatory A2P SMS requirements in United States. Quick Jump: [Numbering Plan](#numbering-plan) [A2P Regulations](#sms-regulations) [Verify US Number](#inspector-cta) [Live United States Inboxes](/receive-sms/us/) Country Dialing Code +1 ISO: US Domestic Trunk Prefix 1 Omitted internationally National Length 10 digits (excluding +1) Local subscriber digits Full E.164 Length 11 digits (+1 NPA-NXX-XXXX) With +1 prefix ## Telephony Architecture & Carrier Allocations Destination Codes: NPA (3-digit Area Code) Mobile Prefix Patterns: Geographic NPA area codes shared between mobile (CMRS) and fixed-line wireline Major Mobile Network Operators: AT&T, Verizon Wireless, T-Mobile US ## A2P Messaging Regulations & Firewall Policies A2P 10DLC & Campaign Registration Mandatory 10DLC campaign vetting via The Campaign Registry (TCR). Unregistered traffic is subject to severe carrier filtering and per-message surcharges ($0.015+). Alphanumeric Sender ID Support Unsupported on standard peer-to-peer or 10DLC routes. Carrier aggregators overwrite alphanumeric headers with dedicated shortcodes or pooled long codes. Two-Way Messaging Capability Fully supported on 10DLC local numbers and verified Toll-Free SMS routes. Character Encoding Standards GSM-7 standard (160 characters/segment). UCS-2 (70 characters/segment) activated on emojis or non-GSM characters. Compliance Framework: CTIA Messaging Principles and Best Practices; TCPA consent verification; SHAFT (Sex, Hate, Alcohol, Firearms, Tobacco) prohibited. Interactive Number Intelligence ### Test a United States Number Now Check if a United States phone number conforms to the national numbering plan, classify mobile vs VoIP allocation, and obtain canonical E.164 standardization. Inspect Number → ## Frequently Asked Questions for United States ### What is the official international dialing code for the United States? The international country calling code for the United States is +1, established under the North American Numbering Plan (NANPA). ### Are Alphanumeric Sender IDs supported for SMS in the United States? No. Major US carriers (AT&T, Verizon, T-Mobile) do not support Alphanumeric Sender IDs. All commercial A2P messaging must originate from a registered 10DLC number, shortcode, or verified Toll-Free number. ### What are the registration requirements for sending A2P SMS in the US? Under US 10DLC regulations, businesses must register their Brand (EIN/Tax ID) and specific messaging Campaigns through The Campaign Registry (TCR) before sending commercial traffic. ### How are US phone numbers formatted in E.164? US numbers in E.164 format start with +1 followed by the 3-digit Area Code (NPA) and 7-digit subscriber number (NXX-XXXX), e.g., +14155552671. ### Related National Calling Codes [Australia +61](/country-codes/australia/) [Austria +43](/country-codes/austria/) [Belgium +32](/country-codes/belgium/) [Brazil +55](/country-codes/brazil/) [Canada +1](/country-codes/canada/) [France +33](/country-codes/france/) [Germany +49](/country-codes/germany/) [India +91](/country-codes/india/) Copied to clipboard FULL PACKET INSPECTION SMS ### Line: DE +49 ... Timestamp: Just now Extracted code Copy Code Message Body: Copy Full Message [Open Live Inbox](#) smsriver.com Central Office carrier inventory platform & developer SMS verification sandbox. Receive OTP codes instantly with zero SIM card requirement. Public numbers·Live inboxes·Developer tools Public Inboxes - [United States (+1)](/receive-sms/us/) - [United Kingdom (+44)](/receive-sms/gb/) - [Canada (+1)](/receive-sms/ca/) - [Philippines (+63)](/receive-sms/ph/) - [Germany (+49)](/receive-sms/de/) Developer & Tools - [SMS Debugging Workbench](/workbench/) - [Phone Number Inspector](/tools/phone-number-inspector/) - [Bulk Phone Validator](/tools/bulk-phone-validator/) - [Phone Lookup API](/developer/phone-lookup-api/) - [E.164 Phone Formatter](/tools/phone-number-formatter/) - [SMS Segment Calculator](/tools/sms-segment-calculator/) - [Webhook Validator](/tools/webhook-payload-validator/) Guides & Trust - [Country Calling Codes](/country-codes/) - [Troubleshooting Hub](/troubleshooting/) - [Carrier Comparisons](/compare/) - [Developer Reference](/developer/) - [OpenAPI Specification](/openapi.json) - [MCP Tools Manifest](/.well-known/mcp.json) - [Privacy & Security Guides](/guides/) - [Engineering Articles](/articles/) © 2026 SMSRiver. Operating on Cloudflare Workers & D1. Adheres to CTIA Messaging Principles and 10DLC compliance standards. [About](/about/) [Contact](/contact/) [Privacy Policy](/privacy/) [Terms of Service](/guides/terms-of-service/) Cookie Preferences