What is floor area ratio?

Total building floor area divided by lot area.

Do basements count toward FAR?

It depends on your zoning code's definition of gross floor area.

Where do I find my FAR?

In your local zoning ordinance or a zoning verification letter.

What is lot coverage?

The share of the lot the building footprint may cover.

Do decks count toward FAR?

Uncovered decks usually don't; covered and enclosed areas often do.

Which limit governs, FAR or coverage?

Whichever gives less area for your lot.

Floor area ratio calculator

Lot area, floor area ratio, maximum lot coverage and number of floors: you get maximum floor area, maximum footprint and the governing area per floor.

Maximum buildable floor area

300 m²

Maximum buildable floor area300 m²
Maximum footprint200 m²
Area per floor (governing)150 m²
Built area with those floors300 m²

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How it's calculated (visible formula)

floor area = lot × FAR; footprint = lot × coverage; per floor = min(footprint; floor area ÷ floors)

Net geometric measurement, no waste.
Adjustable waste % for cuts and breakage.
Purchase rounded up to sellable units (boxes, bags, buckets, boards).

See methodology and formula versions

How to calculate it, step by step

Take lot area from the deed or survey.
Find FAR and lot coverage in the zoning code.
Work out maximum floor area.
Work out maximum footprint.
Split by floors and see which limit governs.

Worked example: 5,380 sq ft lot, FAR 0.6, 40% coverage, 2 floors

Floor area: 5,380 × 0.6 ≈ 3,230 sq ft
Footprint: 40% ≈ 2,150 sq ft
Per floor: min(2,150; 1,615) ≈ 1,615 sq ft

→ About 3,230 sq ft on two floors.

Common mistakes

Confusing FAR (floor area) with lot coverage (footprint).
Ignoring setbacks that shrink the real footprint.
Counting basements or porches when zoning excludes them.

Pro tips

Check setbacks, height limits and story limits too.
Check what counts: basements, porches, covered decks.
Get a zoning letter before buying land.
Survey and tax-record areas may differ.

From calculation to quote

Add labour, overhead and your margin, and generate the professional PDF.

Create quote Calculate margin & GST

FAQs

What is floor area ratio?: Total building floor area divided by lot area.
Do basements count toward FAR?: It depends on your zoning code's definition of gross floor area.
Where do I find my FAR?: In your local zoning ordinance or a zoning verification letter.
What is lot coverage?: The share of the lot the building footprint may cover.
Do decks count toward FAR?: Uncovered decks usually don't; covered and enclosed areas often do.
Which limit governs, FAR or coverage?: Whichever gives less area for your lot.

Sources and standards

Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.