Hello, the MLS in NW Chicagoland requires all bedroom counts be above ground level (no bedrooms in basements) and they needs closets and windows.

Carolyn, if this is a Sugar Land, TX question, our custom here is bedroom must have a door and a closet. The only exception would be a historical home where there never were any closets. In the Houston area, we do not see this very often because we have tended to remodel by bulldozer around here. ;-)

Hello Carolyn. I agree with the others as far as the bedroom definition is concerned. Whether or not having a 4th bedroom will affect the resale value will depend on several things. What's standard in your neighborhood? If most homes have 4 bedrooms, having only 3 may affect the value. I think the size of your house is also important. Having 4 bedrooms packed in a 1,600 sqft house may be considered a negative. If you house is over 2,000 sqft, having a 4th bedroom may be good. These days, many home owners may not care whether the 4th room is a true bedroom as they may use it as an office anyway.

It likely depends on the standard of your MLS. I think you always have to keep the standard buyer in mind. Would you use it as a bedroom? Is it used as a bedroom now? Would most people use it as a bedroom? You might want to have the agent describe the room to clarify it.

On Cape Cod we have septic systems which define the bedrooms of a home - a 3 bedroom septic vs a 4 bedroom septic system. So, if you look at a home that has a 3 bedroom septic system, the home cannot be advertised as a 4 bedroom property even if there is a 4th bedroom. The 4th room would be considered a "bonus room". Having said that, the rule here is, a bedroom is defined by having a window and a closet
(and size of septic system, which you can find out about at the town's health department)

In our MLS system a bedroom is defined as having a closet and a window. Interestingly, there are no minimum standards of size. I have, however, advertised a house as having 4 bedroom potential if there is not a closet. Typically a closet can be added.

In my MLS, a bedroom must have a closet to be considered a bedroom. However, some agents who list older homes classify a room without a closet a bedroom because they never had a closet. In most cases, agents and clients here will expect a closet in a bedroom or will use it to negotiate a lower price.

It really depends on the customs of your town. Take a look at this post:
http://www.trulia.com/voices/Home_Selling/What_is_a_bedroom_…
You'll see how different agents have different opinions.

My suggestion is to have your agent run comps for both 3 bedroom and 4 bedroom homes. If there is a big price difference, I'd avoid calling it a 4 bedroom if you are buying it and state that in your lower priced offer. If there isn't a big difference in price, go with how you would use this room.
Ruth