What happens when an area code runs out of numbers?
Counting down
An area code holds at most 792 assignable prefixes of 10,000 numbers each. NANPA forecasts each code's exhaust date semi-annually from carrier demand filings; those projections appear on every code page of this site. When exhaust threatens before relief can arrive, NANPA declares jeopardy and rations remaining prefixes.
Relief
The state utility commission picks a relief method — today, almost always an overlay. The new code is announced years ahead, a permissive dialing period lets both dialing patterns work, and then ten-digit dialing becomes mandatory. Numbers never 'run out' for consumers; capacity is added before the wall.
Why forecasts move
Pooling efficiency, VoIP growth and demand shifts push dates around: some codes projected to exhaust in the 2020s gained decades from thousands-block pooling alone. Compare a code's current forecast with its overlay history for the fuller story.
Sources
FAQ
Will the US run out of area codes?
Current NANP-wide projections put overall exhaust decades out, with expansion options (longer numbers, new formats) studied well in advance.