Connecticut area codes — detailed data

NANPA NPA database, current as of July 28, 2026.

Full numbering detail for every active Connecticut area code: lineage (which code it split from), NANPA exhaust projections, dialing plans and jeopardy status. This is the working data behind the overview page.

Aggregate footprint: the state's 4 geographic codes currently carry 1,998 active NXX prefixes over 173 rate-center anchorings, with 1,437 prefixes in thousands-block pooling. 4 of the codes serve territory inside FCC top-100 metropolitan statistical areas.

Lineage: 475 came out of 203 in 2009; 860 came out of 203 in 1995; 959 came out of 860 in 2014. The remaining code (203) dates back to the plan's early assignments.

Dialing plans: 4 codes use plain ten-digit local dialing (10D). Overlay territories always dial ten digits; the 2021 988-hotline transition moved most others to ten digits as well.

The tightest capacity in the state is 203 (complex 203/475), projected to exhaust 4Q 2055.

Status: no Connecticut code is currently in jeopardy or active relief planning — capacity is adequate near-term per NANPA.

Code-by-code notes

860 — spawned 959; carved from 203; overlaid by 959; exhaust forecast 1Q 2091.

203 — spawned 860, 475; overlaid by 475; exhaust forecast 4Q 2055.

475 — carved from 203; overlaid by 203; exhaust forecast 4Q 2055.

959 — carved from 860; overlaid by 860; exhaust forecast 1Q 2091.