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San Bernardino County, California
Calculate your Floor Area Ratio and check it against Fontana's limits before you invest in architectural plans. FAR controls how much total building area you can have on your lot — exceed it and your plans will be rejected. Fontana's most common residential zone allows a FAR of varies by zone, which means on a 5,000 sqft lot you can build up to the zone-specific maximum of total floor area.
Provide your lot size in square feet and the floor area of each level of your proposed building. Include garage area if your city counts it toward FAR.
Floor Area Ratio = Total Floor Area ÷ Lot Area. We compare your result against the maximum FAR allowed in your city and zone.
Get a visual gauge showing your FAR usage, remaining buildable square footage, and whether you're over the limit — before you invest in architectural plans.
Floor Area Ratio (FAR) is the total floor area of all buildings on a lot divided by the lot area. It's one of the most important zoning controls — it determines how much total building you can have on your property, regardless of how you distribute it.
For example, on a 5,000 sqft lot with a FAR limit of 0.45:
FAR is different from lot coverage (which only counts the footprint) and height limits (which control how tall). You need to comply with all three independently. A building can be within FAR limits but exceed lot coverage, or vice versa.
This varies by city, which is why FAR can be tricky. Generally:
Note: ADUs may be exempt from FAR calculations depending on your state and local rules. Check with our ADU Eligibility Checker for details.
Note: Some states offer density bonus programs that allow developers to exceed FAR limits in exchange for including affordable units. Check your state and local rules for details.
Lot coverage measures the building footprint (ground floor only) as a percentage of lot area. FAR measures total floor area across all stories. A two-story home on a 5,000 sqft lot with a 1,200 sqft footprint and 1,000 sqft second floor has 24% lot coverage but a 0.44 FAR. You must comply with both limits independently.
It depends on your city. Some cities count attached garages toward FAR but exempt detached garages under a certain size. Others count all garages or exempt required parking areas. This calculator includes garage area — if your city exempts it, your actual FAR will be lower (better) than shown.
Not without a variance or special approval. Options include: applying for a zoning variance (expensive and uncertain), using a density bonus program if your state offers one, or redesigning to stay within limits. In some states, ADUs are exempt from FAR — so adding an ADU won't push you over.
Check your city's zoning map (usually available on the planning department website) to find your zone code, then look up the development standards for that zone. Or use LotCheck's Building Code Lookup to see FAR limits and other zone standards for your city. You can also search your address on our parcel search for property-specific details.
Generally, fully underground basements with no windows or exterior exposure are exempt from FAR. However, "daylight basements" (partially above grade) usually count. Rules vary significantly by city — check your local code.