52 Country Code: Mexico Dialing After the Reform

The 52 country code belongs to Mexico. From the US, dial 011-52 followed by the full 10-digit Mexican number — and that is the whole rule, because Mexico’s August 3, 2019 numbering reform made every number in the country a uniform 10 digits, landline or mobile. The extra prefixes older guides insist on are gone.

That reform is the reason so much advice about calling Mexico is wrong. Most pages still teach the pre-2019 system — a “1” after the country code for cell phones, 044 and 045 for domestic mobile calls — and every one of those instructions now produces a failed or misrouted call. Here is how dialing Mexico actually works today, and why the old way broke.

How to call Mexico from the US today

Dialed from the US, the pieces are:

• 011 — the NANP international exit code (on a mobile, the + sign substitutes for it)
• 52 — Mexico’s country code
• the 10-digit Mexican number — same format whether it rings a desk phone in Polanco or a cell phone in Tijuana

So a Mexico City landline and a Monterrey mobile are dialed identically: 011-52 plus ten digits, twelve digits after the exit code either way. In E.164 format — the shape SIP trunks and dialers insist on — that is +52 followed by the 10 national digits, comfortably inside the standard’s 15-digit ceiling.

If a contact, a website, or a CRM record tells you to insert anything between the 52 and the subscriber number, the instruction predates August 2019. Skip it. The full step-by-step, including worked examples and SMS, is in how to call Mexico from the US.

What the August 2019 reform eliminated

Before the reform, Mexico ran one of the more complicated dial plans in the hemisphere. The prefix depended on what you were calling and from where: 01 for domestic long distance to landlines, 044 for a mobile in your own city, 045 for a mobile in another city, and — the trap for US callers — an extra 1 wedged between +52 and the number when dialing a Mexican cell phone from abroad.

On August 3, 2019, Mexico’s telecom regulator, the Instituto Federal de Telecomunicaciones (IFT), replaced all of it with uniform 10-digit dialing. Every call inside Mexico is now the same ten digits with no prefix. The 01, 044, and 045 prefixes were eliminated outright, and the trailing “1” for mobiles dialed from abroad was retired with them — by 2020 the mobile-vs-landline distinction had disappeared from international dialing entirely.

The result is the simplest rule on our country code list: one country, one format, no exceptions by device type.

The stale-dial-plan problem

Five-plus years on, the pre-reform format still circulates — in old contact lists, printed letterhead, CRM exports, and PBX dial plans written before 2019. A US dialer that auto-inserts “1” after +52 for numbers flagged as mobile is applying a rule that no longer exists, and carriers handle the malformed string inconsistently: some normalize it silently, others reject the call or route it wrong.

The fix is mechanical. Normalize every Mexican number in your system to +52 plus exactly 10 digits, strip any 1, 01, 044, or 045 you find embedded after the country code, and remove mobile-specific translation rules for destination 52 from your outbound dial plan. For call centers running SIP trunking into Mexico, that one cleanup pass eliminates an entire category of failed calls.

Mexico area codes: 55, 81, 33, and the rest

Mexican “area codes” are the first two or three digits of the 10-digit number. The three biggest metros get two-digit codes followed by 8-digit local numbers; everywhere else uses three-digit codes with 7-digit local numbers. Since the reform you dial all ten digits regardless, so the distinction is informational — it tells you where a number is from, not how to dial it.

City code	Metro area
55 (and newer 56)	Mexico City (CDMX)
81	Monterrey
33	Guadalajara
664	Tijuana
222	Puebla
998	Cancún
999	Mérida

So a number beginning 52 55 is Mexico City, 52 81 is Monterrey, 52 33 is Guadalajara. Note that Mexico City has outgrown 55 and also assigns numbers under 56 — both are equally CDMX, much like a NANP overlay.

Calling Mexico for business

Mexico is the destination US contact centers, logistics operations, and cross-border sales teams dial most after domestic traffic, and route quality varies more than the price per attempt does. Answer-seizure ratio, post-dial delay, and correct handling of the post-reform format matter more than any line on a rate sheet.

On cost: rate decks age badly, so we skip them — name your Mexican destinations and we price what we can defend. SIPNEX terminates international traffic over the same SIP trunks that carry your US calls, provisions US DIDs for the inbound side of a cross-border operation, and answers route questions live at (833) 665-2220.

Frequently asked questions

What country uses the 52 country code?

Country code 52 is Mexico — and only Mexico. It covers the entire country under one code, unlike country code +1, which the US shares with Canada and much of the Caribbean under the North American Numbering Plan. A number starting +52 always terminates somewhere in Mexico.

What does the 1 in a saved +52 1 number mean?

It is a pre-2019 artifact, not part of the country code. Contacts saved as +52 1 use the retired mobile format, and some routes reject the extra digit. Normalize every CRM record and dial-plan rule to +52 plus exactly 10 digits — the dialing steps cover the current format.

How do I call the US from Mexico?

Reverse the recipe: dial 00 — Mexico’s international exit code — then 1 for the NANP, then the ten-digit US number, e.g. 00-1-212-555-0123. On a cell phone the + sign replaces the 00. For the opposite direction, worked examples live in our step-by-step guide to calling Mexico from the US.

What is the area code for Mexico City?

55, with newer Mexico City numbers also assigned under 56 — both are equally CDMX. Mexico’s three largest metros use two-digit city codes (55/56 Mexico City, 81 Monterrey, 33 Guadalajara) with 8-digit local numbers; the rest of the country uses three-digit codes with 7-digit numbers. Every call dials the full 10 digits either way.

Are the 044 and 045 prefixes still used in Mexico?

No. The 044 (local mobile), 045 (long-distance mobile), and 01 (domestic long distance) prefixes were all eliminated on August 3, 2019, when Mexico’s regulator IFT moved the country to uniform 10-digit dialing. Any stored number containing those digits after the country code should be cleaned to the bare 10-digit format.

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A 499 filer with direct FCC carrier licensure, SIPNEX terminates US and international traffic over dialer-grade SIP trunking, with local DIDs in every US market and toll-free numbers as a registered RespOrg — every call signed with SIPNEX’s own STIR/SHAKEN certificate. Talk to an operator or call (833) 665-2220.