Why It Matters
Here's why FAR matters: it sets a hard ceiling on how much building you can construct on a parcel. A 10,000-square-foot lot at FAR 2.0 supports 20,000 square feet. Get it wrong in underwriting and your development feasibility collapses. Knowing how to read and push FAR separates investors who find value from those who walk away from workable sites.
At a Glance
- FAR = Total Gross Floor Area ÷ Total Lot Area (FAR 2.0 = two square feet of building per square foot of land)
- Set by local zoning codes — ranges from 0.5 in suburban zones to 20+ in dense urban cores
- Controls building intensity without dictating height or footprint directly
- FAR works alongside lot coverage, setbacks, and height limits — all four constraints apply simultaneously
- Parking structures and below-grade areas are sometimes excluded from FAR calculations (varies by jurisdiction)
- FAR bonuses exist in many cities for affordable housing or green building — check before treating base FAR as the ceiling
- Exceeding FAR requires a variance — a discretionary hearing with no guaranteed outcome
- Gross vs. net floor area definitions differ by jurisdiction — confirm which applies before underwriting
FAR = Total Gross Floor Area ÷ Total Lot Area
How It Works
The formula is simple; the inputs need care. FAR equals total gross floor area divided by total lot area. A 5,000-square-foot lot at FAR 1.5 allows 7,500 square feet — two floors at 3,750 each, or three at 2,500. The formula cares only about the total.
FAR doesn't work alone. You must also satisfy lot coverage limits, setback requirements, and building height limits. A site might support 20,000 square feet under FAR — but after setbacks and height limits apply, you may only build 14,000. Run all four constraints before finalizing buildable area.
Bonus FAR can shift the ceiling. Many jurisdictions offer bonus FAR for affordable housing or green building. Check whether a density bonus applies before treating base zoning as fixed — extra floor area can move a marginal deal to viable.
Variances are discretionary. Exceeding base FAR requires a variance or rezoning — both can be denied. Underwrite to as-of-right FAR and model variance upside separately. The entitlement process rewards patience, not assumptions.
Real-World Example
Lisa tracked a 12,500-square-foot infill lot in Phoenix zoned C-2, listed at $1.87 million. The broker marketed it as a "20,000-square-foot development opportunity." Lisa pulled the zoning code first.
The C-2 zone carried a base FAR of 1.5 — a ceiling of 18,750 square feet. At $185 per square foot in construction cost, that 1,250-square-foot gap was $231,250 in overstated revenue. Yield dropped from compelling to marginal on that one number.
Setbacks of 15 feet front and rear, plus 10-foot side yards, reduced the buildable footprint to about 8,400 square feet. Three floors at 6,250 square feet hit exactly 18,750 — the FAR limit. Configuration locked before architect fees started.
The city's downtown density bonus didn't apply — the site was two blocks outside the boundary. Lisa underwrote at 18,750, repriced, and submitted $140,000 below ask. Accepted two weeks later.
Pros & Cons
- Provides a quantifiable ceiling for development potential before any design work begins
- Allows quick parcel screening without hiring an architect
- FAR bonus programs create upside invisible to buyers who only read base code
- Knowing FAR lets you reverse-engineer land value — a stronger negotiating position
- FAR alone doesn't determine buildable area — setbacks, height, and lot coverage all apply
- Gross vs. net floor area definitions vary by city, creating room for miscalculations
- Variance and rezoning are discretionary and can take 12–24 months with no guaranteed outcome
- In dense markets, base FAR is often already maximized, limiting repositioning upside
Watch Out
Gross vs. net floor area definitions vary. Some cities measure FAR using gross floor area (all enclosed space); others use net (excluding stairwells and mechanical rooms). A 10% definitional gap materially changes your buildable square footage — confirm which applies before building any pro forma.
Parking exclusions are not universal. Many cities exclude structured parking, below-grade space, and mechanical penthouses — others count them fully. If your program includes above-grade parking, verify exclusion rules before assuming those floors are free. One miscounted floor can eliminate a level of rentable space.
FAR and lot coverage are different constraints. FAR measures total floor area relative to lot size; lot coverage measures only the footprint. Both apply independently — underwriting to only one surfaces late in design, after architectural fees are spent.
Ask an Investor
The Takeaway
FAR is the first number you need when evaluating a development site. It translates a raw parcel into a buildable envelope — and that envelope drives every number in your pro forma.
Don't stop at the base number. Check for density bonus programs, and always cross-check FAR against lot coverage and setbacks — the most restrictive constraint defines what you can actually build.