Affordable housing is a term used to describe dwelling units whose total housing costs are deemed "affordable" to those that have a median income. Although the term is often applied to rental housing that is within the financial means of those in the lower income ranges of a geographical area, the concept is applicable to both renters and purchasers in all income ranges. This article focuses on the affordability of owner-occupied and private rental housing as social housing is a specialised tenure.

In the United States and Canada, a commonly accepted guideline for housing affordability is a housing cost that does not exceed 30% of a household's gross income. Housing costs considered in this guideline generally include taxes and insurance for owners, and usually include utility costs. When the monthly carrying costs of a home exceed 30–35% of household income, then the housing is considered unaffordable for that household.

Affordability by country

United States

Comprehensive data for the most affordable and least affordable places in the U.S. is published each year by an affordable housing non-profit organization, the National Low Income Housing Coalition. The NLIHC promotes a guideline of 30% of household income as the upper limit of affordability.

Under this definition, most people in the United States have secured affordable housing arrangements. In 2001, the median household paid $658 per month in total housing costs. A total of 20% of households are deemed to be living in unaffordable housing: Nine percent of all households are renters in unaffordable housing, and eleven percent of all households are homeowners with high housing costs.