Check a site’s floor space ratio in seconds
Enter a site area and a gross floor area to get the FSR, see the floor area a planning control allows, and find how much capacity is left. A quick planning check before a full feasibility.
The site
Planning control (optional)
Enter the maximum FSR from the control to see the allowed floor area and how much is left.Capacity ladder
Allowed gross floor area on this 1,000 sqm site across common FSR controls. The dashed line is your GFA — bars past it have headroom, bars short of it sit over that control.
Exhibit · allowed GFA = site area × FSR. A first-pass read on capacity, not a yield or a design. Setbacks, height, parking and efficiency decide what actually fits.
Floor space ratio (FSR) is the gross floor area divided by the site area, written as a ratio like 1.5:1. This free Popurise calculator works out the FSR, multiplies a permitted FSR by the site to show the allowed floor area, compares it to your GFA for the headroom or excess, and can size a site for a target. It is a planning-metric estimate for early screening, not planning advice.
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What the result means
An FSR of 1.5:1 means the floor area is 1.5 times the site
Floor space ratio compares two areas: the floor area you build and the land you build on. A ratio of 1.5:1 means the gross floor area is 1.5 times the site area, so a 1,000 square metre site with a 1.5:1 ratio carries 1,500 square metres of floor.
That floor area is the total across every level, not the height. A 1.5:1 site could be a low building that covers most of the block, or a taller building on a smaller footprint. The ratio caps the floor area; the design decides how it is arranged.
When you enter a permitted FSR, the calculator multiplies it by the site to show the floor area the control allows, then compares it to your GFA. A positive number is spare capacity; a negative one means the plan is over the cap.
The floor area is 1.5 times the size of the land. Spread it over two levels and each covers about three-quarters of the site; over three, about half.
Show the maths
Three relationships, one control
Floor space ratio is one division, and the two questions around it are the same relationship rearranged. Site area and floor area go in, a ratio or an area comes out.
Why it matters in a feasibility
How the number flows into the deal
FSR is an upstream input. It sets the floor area a site can hold, and that floor area ripples all the way down to the land price and the return.
FSR sets the buildable floor area
The permitted FSR and the site area fix the gross floor area a site can hold. That is the starting point of yield: how many dwellings, how much space, how big the project is.
Residential feasibility calculatorFloor area drives cost and revenue
Construction cost is priced per square metre of GFA. An efficiency ratio turns GFA into saleable or lettable area, and that area, at a rate per square metre, becomes gross realisation.
Residential development feasibilityWhich sets residual land value
Take gross realisation, remove build cost, fees, finance, selling costs and the target return, and what is left is what you can pay for the land. Floor area sits at the top of that chain.
Residual land value calculatorTest it in the full model
Planning capacity is not a feasible project until timing, debt, cash flow and the design are modelled. Move a promising site into the full workflow before you commit to a land price.
Feasibility softwareCommon mistakes
Where a quick FSR read goes wrong
The ratio is simple. The mistakes are in what it quietly leaves out — so treat these as the checks before you trust a capacity number.
Confusing GFA with saleable area
Gross floor area is not what you sell or lease. Saleable area (NSA) and lettable area (NLA) are smaller, after cores, common areas and walls. Use GFA for the ratio and cost, saleable area for revenue.
Ignoring the control's exclusions
Most controls exclude parking, plant, cores and often balconies from GFA. Skip the exclusions and you either understate capacity or count area the control never intended.
Treating the maximum FSR as the yield
The maximum FSR is a ceiling, not a delivered building. Assuming a site achieves its full FSR before testing the design overstates the floor area and every number that follows.
Forgetting setbacks, height and parking
Height limits, setbacks, building separation, overshadowing and parking can all bind before the FSR does. A site can be short of its FSR because the envelope, not the ratio, is the constraint.
Using capacity without testing the numbers
Floor area a site can hold is not the same as a deal that works. Planning capacity has to survive construction cost, revenue, finance and the target return before it means anything.
Mixing up FSR and site coverage
FSR limits total floor area across all levels; site coverage limits the footprint on the ground. A site can be tight on one and loose on the other, so check both against the control.
Worked example
An illustrative site, end to end
Example only. Illustrative numbers, not planning advice.
- Site area
- 1,000 sqm
- Gross floor area
- 1,500 sqm
- Permitted FSR
- 2.0:1
Questions
Answered
What FSR is, how it is worked out, what a ratio like 1.5:1 means, and where it stops being a planning number and becomes a feasibility one.
- What is floor space ratio?
- Floor space ratio (FSR) is the amount of building floor area allowed on a site relative to the size of the site. It is a planning control that limits development density. An FSR is written as a ratio, such as 1.5:1, where the first number is the floor area and the second is the site. It is also called floor area ratio or plot ratio.
- How do you calculate FSR?
- Divide the gross floor area by the site area. FSR = gross floor area ÷ site area. A 1,500 sqm building on a 1,000 sqm site is 1,500 ÷ 1,000 = 1.5:1. To work the other way, multiply the site area by the permitted FSR to get the floor area a control allows: allowed GFA = site area × permitted FSR.
- What does 1.5:1 FSR mean?
- An FSR of 1.5:1 means the gross floor area is 1.5 times the site area. On a 1,000 sqm site, a 1.5:1 ratio allows 1,500 sqm of floor area. That floor area can be spread across several storeys, so a 1.5:1 site is not a one-and-a-half storey building; it is the total floor area that matters, not the height.
- Is FSR the same as gross floor area?
- No. Gross floor area (GFA) is a floor area in square metres. FSR is a ratio that compares that floor area to the site area. GFA is one of the two numbers used to work out FSR; the other is the site area. A control usually sets a maximum FSR, and the allowed GFA follows from the size of the site.
- Does FSR include balconies, parking or basement areas?
- It depends on the planning scheme. Most controls exclude some areas from GFA, commonly basement parking, plant, lift cores, and often balconies, but the exact exclusions vary by council and state. Always read the definition of gross floor area in the relevant control before you rely on a number, because the exclusions change the floor area a site can hold.
- Can I build to the maximum FSR?
- Not always. The maximum FSR is a ceiling, not a guarantee. Height limits, setbacks, parking, overshadowing, building separation, site shape and design quality can all stop a site from reaching its FSR. Treat the maximum as the upper bound and test what actually fits before assuming the full floor area is achievable.
- Why does FSR matter in a development feasibility?
- FSR sets how much floor area a site can hold, which sets the saleable or lettable area, the construction cost and the gross realisation. Those flow into residual land value and the project return. Get the FSR and the floor area wrong and every number downstream is wrong, so it is one of the first inputs to pin down when screening a site.
- Does this calculator replace planning advice?
- No. This is a planning-metric estimate for early screening, not planning advice. FSR rules vary by planning scheme, council, site constraints and project design, and controls carry exclusions and bonuses this tool does not read. Check the relevant planning controls and speak with a qualified planner before making decisions.
Turn planning capacity into a real feasibility.
FSR tells you how much floor area a site could hold. Popurise turns that into yield, cost, revenue, residual land value and return across the whole deal. Free right now, no card required.