Planning & Budgeting
Floor Space Ratio (FSR) Calculator
Calculates FAR and site coverage percentage for planning
Updated 26 June 2026 · Live
What this tool does
Calculates the Floor Space Ratio (FSR/FAR) — gross floor area divided by plot area — and expresses that same ratio as a percentage for planning reference.
Floor Space Ratio (FSR) Calculator — enter your gross floor area of {gross_floor_area_m2} m² and plot area of {plot_area_m2} m² to get an estimated FSR of {result}.
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Formula Used
How the floor area ratio / plot ratio calculator works
Calculates FAR and site coverage percentage for planning. The calculator takes your dimensions and supplier rates, applies a standard Australian trade formula, and returns a quantity with an indicative cost. Every figure is an estimate — site conditions always move the final number.
Typical Australian planning and budgeting wastage
Budget "wastage" is called contingency. Typical allowances: 10% on a new kitchen/bathroom, 15% on a single-storey extension, 20%+ on heritage-listed or change-of-use work. Our defaults reflect common Australian trade allowances, and can be adjusted upwards for non-standard geometry or downwards where experience supports a lower figure.
What this tool does not do
It does not replace a professional quote, factor regional pricing, assess structural adequacy, or confirm National Construction Code (NCC) compliance. Those remain the responsibility of a suitably qualified designer, surveyor, or your building surveyor.
On-site considerations for floor area ratio / plot ratio
Fixed-price quotes are rare on renovation work. Most jobs are let on a schedule of rates with a provisional sum for unknowns — understand which model your contractor is using.
the National Construction Code (NCC) and compliance
Domestic projects over $100,000 that involve more than one contractor are notifiable under the WHS Regulations. The client (you) has legal duties even on a domestic project. When in doubt, a pre-application enquiry to the local council can give early clarity, which tends to be less costly than retrospective correction.
Before you order
Collect three written quotes on identical specifications. Verbal quotes are effectively unenforceable if the job then goes wrong. Cross-checking the calculator’s output against a supplier quote helps catch differences in pricing assumptions — ask for exact product specifications (grade, finish, batch number) and confirm delivery timescales against your programme.
Adjusting the defaults
Every input in this calculator is editable. Enter your own dimensions, supplier prices, and wastage allowance — the output recalculates instantly. If the defaults feel off for your region or project type, your own numbers always override them.
Using this floor area ratio / plot ratio calculator alongside other BuildMetricLab tools
This calculator works best as part of a planning workflow. Pair the quantity with our project contingency, labour-hours, and material-cost calculators to build a complete estimate before you pick up the phone to a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.
Sources & methodology
Calculates FAR and site coverage percentage for planning. Every result is calculated from the values you enter, and all inputs are editable.
Frequently asked questions
Are FSR/FAR calculator results accurate enough for a planning application?
Use this result as an initial estimate only. Councils and the NCC may define gross floor area and site area differently for compliance purposes, so verify the exact figures with your local planning scheme (LEP/DCP) or a town planner before lodging an application.
What counts as gross floor area and plot area?
Gross floor area is the total enclosed floor space across all storeys of the building, and plot area is the total site area. Both should be measured consistently — check your local council's planning scheme or the NCC for the specific definitions that apply to your application.
Does this tool replace professional planning advice?
No — this tool provides a planning estimate only. For matters affecting structure, the National Construction Code (NCC), boundary or dividing-fence rules, gas, electrics, drainage to a sewer, or similar, consult a suitably qualified professional such as a town planner or chartered engineer.
What is a good FSR/FAR for my site?
Acceptable FSR/FAR values vary widely by zoning, lot size and local planning controls. There is no single 'good' figure — check your council's local environmental plan (LEP) or development control plan (DCP) for the maximum ratio permitted on your site.
Spotted something off?
Calculations or display — let us know.
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