Area code 203: Connecticut
What is area code 203?
Area code 203 is a US state area code for Connecticut, on Eastern Time. It has 784 prefixes in service across 32 rate centers, the largest being New Haven, Stamford and Bridgeport. It shares its area with 475, so local numbers there can start with any of them. Local calls there take 10 digits.
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See the phone add-onArea code 203 facts
| Location | Connecticut, United States |
|---|---|
| Time zone | Eastern Time |
| Overlays | 475 |
| In service since | 1947, when the plan began |
| Local calls | 10 digits; toll calls 1 + 10 digits |
| Carrier | Not shown. An area code is where a number was issued; numbers port between carriers. Check line type |
In short: 203 is Connecticut (Eastern Time). Format checks here are free and run in your browser; the current carrier and line type need a live lookup. Bulk phone number validator · Pro + Phone plan
Local time in area code 203
America/New_York
Prefixes in service
784 of 792 possible
32 rate centers
Which cities and towns use area code 203?
NANPA records each prefix against a rate center, the local billing area a number belongs to, usually named after its main town. These are the 203 rate centers with the most prefixes in service. 20 smaller ones aren't listed.
| Rate center | Prefixes |
|---|---|
| New Haven | 145 |
| Stamford | 97 |
| Bridgeport | 94 |
| Norwalk | 60 |
| Danbury | 54 |
| Waterbury | 52 |
| Greenwich | 27 |
| Meriden | 24 |
| Ansonia-Derby | 17 |
| Westport | 16 |
| Darien | 15 |
| Fairfield | 15 |
Source: NANPA central office code assignments, file dated 10/17/2026. Each prefix holds up to 10,000 numbers.
How do I dial a 203 number?
NANPA's dialling plan for 203: local calls inside the code take 10 digits, toll calls 1 + 10 digits. From another area code, dial 1 first. From abroad, use +1. The examples use 555-0147, from a range reserved for fictional numbers.
| Local call inside 203 | 203-555-0147 |
|---|---|
| From another US or Canadian area code | 1-203-555-0147 |
| From outside North America | +1 203 555 0147 |
| E.164, for CRMs and SMS tools | +12035550147 |
When did area code 203 start?
Area code 203 is one of the original codes NANPA lists from 1947. Today 203 and 475 cover the same area as an overlay, which is why 10-digit dialling is needed for local calls there.
Tools for 203 numbers
- Bulk phone number validator
Format, country and number type for every number in a CSV, with E.164 output.
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- Area code time zone
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- NPA-NXX lookup
Rate center and state for one prefix, a level below the area code.
- TCPA calling hours checker
Whether it's inside the federal 8 a.m. to 9 p.m. calling window there now.
Next step
A 203 number tells you where it was issued, not what it is now.
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Area code 203 questions
- What state is area code 203?
- Area code 203 is in Connecticut, United States. Its largest rate centers by number of prefixes are New Haven, Stamford, Bridgeport, Norwalk and Danbury.
- What time zone is area code 203 in?
- Eastern Time.
- What area codes overlay 203?
- 475. An overlay adds a new code to the same area instead of splitting it, so neighbours can have different area codes and local calls need 10 digits.
- When did area code 203 start?
- Area code 203 is one of the original codes NANPA lists from 1947.
- Is a 203 number a cell phone or a landline?
- The area code can't tell you. In the US and Canada mobiles, landlines and VoIP lines share area codes and prefixes, and numbers move between carriers and line types. Only a live line-type lookup answers it for one number.
- How many phone numbers does area code 203 have?
- 784 of its 792 possible prefixes are in service, and each prefix holds up to 10,000 numbers. That counts prefixes assigned to carriers, not numbers in use.
- Does a valid format mean a 203 number is in service?
- No. A format check only says the digits fit the North American Numbering Plan and that 203 is an assigned code. It cannot tell whether the number is connected, who answers it or which carrier serves it today, because numbers are reassigned and ported. A live carrier lookup reports the current carrier and line type, but even that is not proof someone answers.
- Can I check a list of 203 numbers for free?
- Yes. Paste them in the list tab above or upload a CSV to the bulk phone number validator: format, E.164, country and the numbering-plan line type are free for every row, with no account. Live carrier and line-type lookups come with Pro + Phone at $49.99/mo (5,000 a month).
Other area codes in Connecticut
All Connecticut area codes on the area code index.
Sources
Location, overlays, in-service date and dialling plan: NANPA NPA database, file dated 10/16/2026. Prefixes and rate centers: NANPA central office code assignments, 10/17/2026. Time zones mapped to the IANA time zone database. By the SimpleVerifier Team; how we build these pages.