Site Size Calculator
Enter the site area, the maximum site coverage and the floor area ratio from your zoning or planning rules. The calculator gives the largest footprint, the total floor area and how many floors that means.
- Maximum floor area
- Footprint
- Floors
Find coverage and FAR in your local zoning or planning code.
Floor area = site area × FAR, footprint = site area × coverage. A 20,000 sq ft site with 40% coverage and a FAR of 1.2 allows an 8,000 sq ft footprint and 24,000 sq ft of floor area, which is 3 full floors.
Floor area by FAR
For a 20,000 sq ft site at 40% coverage. Search for a FAR.
| FAR | Floor area | Floors |
|---|---|---|
| 0.5 | 10,000 | 1.2 |
| 0.8 | 16,000 | 2.0 |
| 1 | 20,000 | 2.5 |
| 1.2 | 24,000 | 3.0 |
| 1.5 | 30,000 | 3.8 |
| 2 | 40,000 | 5.0 |
| 3 | 60,000 | 7.5 |
| 4 | 80,000 | 10.0 |
Square feet.
FAR and floors
20,000 sq ft site, 40% coverage. Slide the FAR.
The footprint is drawn on the site.
How to size a site
Zoning to building. Step through it.
Area
Measure the site.
Setbacks from the boundary can shrink the real footprint.
Coverage, FAR or height
Zoning limits. Compare them.
Footprint.
Floor area.
Height.
Whichever limit is tightest decides the building.
Before you design
Site checks. Tick each item.
Tick each item as you go.
Ask the planning office for a zoning letter on the site.
What you get
Site sizing. Each tile explains one result.
Total.
Ground floor.
Count.
Left.
Rough count.
A higher FAR with low coverage means a taller building.
Frequently Asked Questions
No question matches that search.
What is floor area ratio?
The total floor area of a building divided by its site area.
What is site coverage?
The share of the site the building's footprint covers.
How many floors can I build?
Divide the allowed floor area by the footprint.
Does FAR include basements?
Usually not, but the rule varies between councils.
What is plot ratio?
Another name for floor area ratio, used in the UK and Asia.
Where do I find my zoning limits?
In the local zoning code or planning policy for your district.
Know what fits
Check coverage and FAR first and you know how big you can build.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.