Get a local business phone number in Black Diamond, WA

What area code is Black Diamond, WA?

Black Diamond city is a Census place in King County, Washington, with an estimated 6,787 residents in 2024. All 4 exchanges NANPA lists for its rate center are in area code 360. 360 is part of an overlay with 564, so a new local number in Black Diamond may carry any of those codes depending on which have numbers available. Black Diamond is in the Pacific time zone.

According to NANPA's dialing-plan data, local calls within 360 are dialed as ten digits (area code plus number) and toll calls as 1 plus ten digits.

Phone carriers in Black Diamond

3 carriers hold the 4 exchanges assigned to Black Diamond's rate center. Onvoy, LLC - Wa has the most, with 2. 4 of them are pooled codes, which the holder shares with other carriers in blocks of 1,000 numbers. A business number in Black Diamond can come from any of these blocks; once it is yours, porting lets it move between providers.

Local prefixes for Black Diamond

Each prefix below is a block of up to 10,000 numbers that NANPA assigned to Black Diamond's rate center (BLACKDIMND). The earliest assignment date recorded in the file for these codes is 2001. None were assigned in 2020 or later.

When Black Diamond's exchanges were assigned

The table groups Black Diamond's exchanges by the decade NANPA recorded them as assigned.

Rate centers and local calling in Black Diamond

What a caller sees as "local" is the area code plus prefix. In Black Diamond, those come from the BLACKDIMND rate center, as recorded by NANPA.

If your business already has a Black Diamond number, porting it to Callata is free and keeps it on your cards, listings and vehicles.

Businesses around Black Diamond

Black Diamond is part of the Seattle-Tacoma-Bellevue, WA metro area, home to 4.1 million people in 2024. County Business Patterns counted 110,685 business establishments in the Seattle, WA metro area in 2023, employing 1,884,361 people. The largest sectors by establishment count are professional, scientific, and technical services (14,812), construction (13,610), and health care and social assistance (13,557).

Setting up a Black Diamond business line

For $99 a month, Callata puts a team of up to 5 on one plan ($20 for each person after that): up to 3 local numbers, unlimited inbound calls, a pooled allowance of 1,500 outbound US and Canada minutes per user, browser and cell calling, voicemail transcription with urgency triage, recorded calls with AI summaries and business-hours routing, with E911 on every number.

Porting a number you already use in Black Diamond is free, and business texting is available once the carrier registration (10DLC) is approved; the registration carries a one-time $49 fee. Which specific numbers are open in a given area code depends on carrier inventory at the time you sign up.

AI agents are optional: an AI receptionist or scheduler can pick up when the team is busy or closed, take a message, send a text or email, or transfer the call. They draw on prepaid AI minutes ($0.25/minute), disclose that they are AI, and outbound AI calls require prior consent and are limited to 8am–9pm.

A 17-person team is the benchmark here, the rounded average establishment size in the Seattle, WA metro area. Billed per seat at month-to-month list prices (checked September 28, 2026), RingCentral RingEX Core costs $510.00 a month and Ooma Office Pro $424.15. Callata comes to $339.00 a month for 17 users ($99 a month with 5 users included, then $20 per additional user), below both.