Floor area ratio
The floor area ratio (FAR), also known as the plot ratio, is a measure of the total permitted floor area of a building, in relation to the total area of the lot (or plot) on which the building stands:
Gross floor area of all floors of the building / Area of the building lot = FAR
A higher ratio indicates a higher-density environment.
The concept emerged in Europe in the 19th century, and was then taken up in the USA in the 20th century as a form of zoning control for rapidly developing cities. FAR is now often used by urban planners, particularly in the USA, for assessing, or restricting, planning permissions, setting a limit on the 'load factor' generated by new developments, beyond which undue stress is placed on a city and its infrastructure.
A low permitted FAR may deter development, whilst a higher FAR allows more usable area, and hence higher potential sales.
The same FAR value can be achieved by buildings with varying numbers of storeys. For example:
1,000 sq. m building with one storey / 4,000 sq. m lot = 0.25
500 sq. m building with two storeys / 4,000 sq. m lot = 0.25
An FAR of 1.0 allows the developer to build a one-storey building over the lot, or a two-storey building over half the lot, or a three-storey building over one-third of the lot, and so on.
An FAR of 2.0 allows the developer to build a two-storey building over the lot, or a four-storey building over half, and so on.
Bradford City Centre Design Guide, Supplementary Planning Document, published in 2006, defines plot ratio as: ‘A measure of density for non-residential use. This is expressed as a ratio in which the first number relates to the floor area of the building and the second to the area of the site. A 2:1 ratio therefore denotes a building that has two times the floor area of the site. This could be a two storey building covering the entire site or a four storey building covering half of the site.’
NB Land measurement for planning and development purposes, Guidance Note, Global 1st edition, Published by the Royal Institution of Chartered Surveyors (RICS) in May 2021, defines plot ratio (PR) as: ‘…the ratio of total development floor area to site area. Development floor area may be measured as gross external area (GEA) or gross internal area (GIA), but whichever is used – or modifications of them – should be clearly stated. Gross external area and gross internal area are defined in Property measurement, RICS professional statement.’ It suggests that floor area ratio (FAR) and floorspace ratio (FSR) are similar terms.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
SELECT three-point plan for action issued to MSPs
Call for Scottish regulation, green skills and recognition of electrotechnical industry as part of a manifesto for Scottish Parliamentary elections.
UCEM becomes the University of the Built Environment
Major milestone in its 106-year history, follows recent merger with London School of Architecture (LSE).
Professional practical experience for Architects in training
The long process to transform the nature of education and professional practical experience in the Architecture profession following recent reports.
A people-first approach to retrofit
Moving away from the destructive paradigm of fabric-first.
International Electrician Day, 10 June 2025
Celebrating the role of electrical engineers from André-Marie Amperè, today and for the future.
New guide for clients launched at Houses of Parliament
'There has never been a more important time for clients to step up and ...ask the right questions'
The impact of recycled slate tiles
Innovation across the decades.
EPC changes for existing buildings
Changes and their context as the new RdSAP methodology comes into use from 15 June.
Skills England publishes Sector skills needs assessments
Priority areas relating to the built environment highlighted and described in brief.
BSRIA HVAC Market Watch - May 2025 Edition
Heat Pump Market Outlook: Policy, Performance & Refrigerant Trends for 2025–2028.
Committing to EDI in construction with CIOB
Built Environment professional bodies deepen commitment to EDI with two new signatories: CIAT and CICES.
Government Grenfell progress report at a glance
Line by line recomendation overview, with links to more details.
An engaging and lively review of his professional life.
Sustainable heating for listed buildings
A problem that needs to be approached intelligently.
50th Golden anniversary ECA Edmundson apprentice award
Deadline for entries has been extended to Friday 27 June, so don't miss out!
CIAT at the London Festival of Architecture
Designing for Everyone: Breaking Barriers in Inclusive Architecture.
Mixed reactions to apprenticeship and skills reform 2025
A 'welcome shift' for some and a 'backwards step' for others.