Hong Life CalculatorsUnderstanding the floor area ratio calculator — concept and principle
This calculator works out a building's floor area ratio (FAR, 용적률) and building coverage ratio (BCR, 건폐율) from the site area, the building footprint and the total floor area, and compares them with the national caps for Korean land-use zones. Landowners, architects and buyers use it for a first check of how much can be built on a plot.
How it is calculated
- FAR (%) = total floor area counted for FAR ÷ site area × 100.
- BCR (%) = building area (footprint seen from above) ÷ site area × 100.
- Maximum floor area at the FAR cap = site area × cap ÷ 100; maximum footprint at the BCR cap likewise.
- Floors if every floor equals the footprint = total floor area ÷ footprint.
- Caps are the national upper limits by zone; for Category 2 general residential they are BCR 60% and FAR 250%.
The principle
FAR limits how much floor space, and so how many people and how much traffic, a plot can carry. BCR limits how much of the plot the building covers, keeping space for light, air and greenery. Together they shape density: a tall slim building and a low wide one can share the same FAR but differ in BCR. Under the Korean Building Act, floor area for FAR leaves out basements, ground-floor parking that serves the building and a few other spaces, so use the above-ground floor area. The decree to the National Land Planning and Utilization Act sets upper limits for each zone, and cities and counties set their own, usually lower, limits by ordinance.
Worked example
Default inputs: site 330 m², footprint 165 m², above-ground floor area 560 m², Category 2 general residential zone.
- FAR = 560 ÷ 330 × 100 = 169.7%.
- BCR = 165 ÷ 330 × 100 = 50%.
- National caps: BCR 60%, FAR 250%.
- Maximum floor area = 330 × 2.5 = 825 m²; maximum footprint = 330 × 0.6 = 198 m².
- Floors = 560 ÷ 165 = 3.4; within the caps: yes — check your local ordinance too.
| Site area (m²) | Floor area ratio (FAR) |
|---|---|
| 82.5 | 678.8% |
| 165 | 339.4% |
| 248 | 226.3% |
| 330 | 169.7% |
| 412 | 135.8% |
| 495 | 113.1% |
| 660 | 84.8% |
How to read the result
Being within the national caps is only the first test. The city or county ordinance usually sets a lower FAR, and district unit plans, height limits, road width, sunlight rules and parking requirements can reduce the buildable area further. Then confirm with the local planning office.
Common mistakes
- Including basement floors in the FAR floor area.
- Using the national cap instead of the local ordinance.
- Confusing building area (footprint) with total floor area.
- Using the land area on a sale listing that differs from the registered site area.
Frequently asked questions
What is the difference between 용적률 and 건폐율?
FAR (용적률) compares total floor area with the site; BCR (건폐율) compares the footprint with the site.
What is the FAR cap for Category 2 general residential zones?
The national upper limit is 250%, but local ordinances usually set a lower figure.
Do basements count toward FAR?
No. Under the Building Act, basement floors are excluded from the floor area used for FAR.
Sources: Building Act (건축법) Articles 55 and 56; Enforcement Decree Article 119 · Enforcement Decree of the National Land Planning and Utilization Act (국토의 계획 및 이용에 관한 법률 시행령) Articles 84 and 85