It varies according to the room. First, here’s a list of receptacle requirements for rooms where a simple, minimum number is specified. Click on the links after each citation for more details:
Bathrooms - Minimum of one per bathroom sink, within three feet. What is code for bathroom reptacle outlet spacing? .
Hallways - Minimum of one per hallway if ten feet or longer.  How many electrical receptacles (outlets) are required in a hallway?
Garages - Minimum of one receptacle. How far apart should electric receptacle outlets be placed in a garage?
Exterior - Minimum of two receptacles, one each front and back. Is a house required to have outdoor electric receptacle outlets?
Closets - Not required. What is the code requirement for receptacle outlets in a closet?

Now, the more complicated minimum receptacle standards:
Living Room, Dining Room, Bedroom, Den, Sun Room, etc. - The maximum spacing between receptacles in general living areas is 12 feet, with no point along a wall being more than 6-feet from a receptacle. What is code for receptacle outlet spacing?   
Kitchens - Minimum two 20-amp circuits for kitchen appliances, and counter receptacles spaced so that no point along the back of counter is more than two-feet from a receptacle. How far apart should kitchen counter receptacles be spaced? 
Foyers - Foyers that are not part of a hallway and are greater than 60 square feet require a receptacle outlet on each wall space that is 3 feet or more in width, What is the code requirement for receptacle outlets in a foyer?

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  To learn more about electrical wiring, devices, and receptacles, see these other blog posts:

 • What is the difference between what trips a GFCI (ground fault) receptacle and a circuit breaker?

• What is the code requirement for GFCI protection for receptacles near a wet bar sink? 

• What is the requirement for a service receptacle outlet for heating, air conditioning, and refrigeration (HACR) equipment? 

• Why is an opening in the wall around the side of an electrical receptacle outlet a safety defect?  

• When should I replace electric receptacle outlets? 

• Does an electric receptacle outlet in a storage shed require GFCI protection? 

• What are "self-contained" electrical receptacle outlets and switches?

• What is the difference between an electrical receptacle, an outlet, and a plug?

• What is a "backstab" receptacle outlet? 

• Why are some electric receptacle outlets upside down (ground slot up) in a house?   

• What is the height requirement for an electric receptacle outlet? 

• What is the minimum height for an exterior receptacle outlet? 

• When was the current receptacle/outlet spacing of 12-feet first required? 

• When was the three-slot (grounding) outlet/receptacle first required? 

• Why does painting an electric receptacle (outlet) make it unsafe?

• Why are electrical outlets and plugs polarized?  

• What problems does having too many electric receptacle outlets on a single circuit cause? 

• How I can tell if a receptacle outlet is tamper resistant?

• Why is there a GFCI breaker in the electric panel for the bathroom shower light and exhaust fan?

• What is a false ground, bootleg ground, or cheated ground receptacle? 

• How can adding wood paneling or a wainscot create an electrical safety hazard?

• How can I figure out what a mystery wall switch does?  

• How high above the floor do electric outlets/receptacles in a garage have to be?

• Is an ungrounded electric receptacle outlet dangerous?

• My bathroom electric receptacle/outlet is dead and there are no tripped breakers in the electric panel. What's wrong?  

• Is there an adapter that can be placed on a two-slot receptacle to make it safe? 

• How do the new tamper-resistant electric outlets work?

• Why is there no bathroom electric receptacle in this old house?

• How can I tell if the electric receptacle outlets are grounded? 

• How far apart should the electrical receptacles be placed?

• What are the most common problems/defects found with electric receptacle outlets during a home inspection?

   Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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