One sub-centre covers:
1000 population
2000 population
4000 population
5000 population
The sub-centre is the peripheral outpost of the existing health delivery system in rural areas. 
One sub-centre covers a population of 5000 in general and 3000 in hilly, tribal and backward areas. 
The functions of a sub-centre are limited to mother and child health care, family planning and immunization. 
There are two functionaries at the level of the subcentre: one male and one female multipurpose health worker. 
One health assistant (HA) will supervise the work of 6 health workers. 
Six subcentres are located in each PHC area.

Essentials of preventive and community dentistry
Soben Peter
5th edition
Page number 226