FSI calculator: how much can you build on your plot?
The floor space index (FSI) — called floor area ratio (FAR) in most Indian states and the US, and floor space ratio (FSR) in New South Wales — is the total floor area a building may have divided by the area of its plot. This FSI calculator works in both directions: from the plot area and the FSI your rules allow (base FSI plus any premium FSI, TDR and fungible area) it gives the maximum built-up area, and from a design’s floor areas it gives the FSI the design actually uses and whether it fits.
It is useful to plot buyers, owners planning redevelopment, architects checking a scheme and anyone comparing what different plots can yield. Enter your city’s own figures, or start from the Mumbai DCPR 2034 table built in. Everything runs in your browser. Results are estimates for planning: what is permitted on a particular plot is decided by the planning authority under its current regulations, so treat this as a first check, not professional advice.
How to use the FSI Calculator
- Choose Permissible built-up area or FSI used by a design.
- Enter the Plot area and pick sq m, sq ft or sq yd.
- Pick a Rule set: your own figures, or Mumbai DCPR 2034 with the Road width in front of the plot.
- For permissible area, enter or check the Base (zonal) FSI, Premium FSI, TDR, any Fungible / compensatory area and, optionally, the Maximum ground coverage to estimate floors.
- For a design, list the Floor areas counted in FSI (for example “4 x 250”), the Areas exempt under your rules and the Permitted FSI / FAR.
FSI Calculator features
Base + premium + TDR
Builds the total FSI from its parts and shows the built-up area each part adds.
Mumbai DCPR 2034 presets
Island City and suburban figures by road width from Table 12 of the sanctioned regulations, editable after loading.
FSI, FAR and FSR together
Shows the same number as a ratio (2.0), the percentage form used in many FAR tables (200) and the NSW style (2:1).
Design check
Adds up floor plates, subtracts exempt areas and tells you how much permitted floor area is left — or by how much a design is over.
FSI formula
FSI (FAR) = total built-up floor area ÷ plot area, so maximum built-up area = plot area × FSI. A 1,000 sq m plot with an FSI of 2.0 allows 2,000 sq m of floor area: two floors covering the whole plot, five floors covering 40% of it, and so on. Where FSI is built from parts, the total is base (zonal) FSI + premium FSI bought from the authority + TDR (transferable development rights loaded from elsewhere). Some regulations then allow an extra percentage on top — Mumbai’s “fungible compensatory area”.
What counts is local. Each development control regulation (DCR), zoning code or local environmental plan lists areas that are excluded from floor area — commonly staircases and lift wells, parking floors, basements, some balconies and service ducts — and the list differs between cities and changes with amendments. In New South Wales, clause 4.5 of the Standard Instrument LEP defines FSR as gross floor area divided by site area, while each council’s FSR map sets the maximum. This calculator does not guess exclusions: enter the area your rules exempt.
Mumbai FSI under DCPR 2034 (Table 12)
Residential and commercial zones, as sanctioned by the Government of Maharashtra on 8 May 2018 (regulation 30(A)(1), Table 12). Permissible FSI = zonal (basic) + premium + admissible TDR. Source: DCPR 2034 published by the Municipal Corporation of Greater Mumbai, read October 2026. The regulations have been amended since and special schemes (for example redevelopment under regulation 33) follow their own tables, so confirm the current figure for a specific plot.
| Road width | Island City | Suburbs and extended suburbs |
|---|---|---|
| Up to 9 m | 1.33 | 1.0 |
| Over 9 m up to 12.20 m | 1.33 + 0.34 + 0.33 = 2.0 | 1.0 + 0.5 + 0.5 = 2.0 |
| Over 12.20 m up to 18.30 m | 1.33 + 0.62 + 0.45 = 2.4 | 1.0 + 0.5 + 0.7 = 2.2 |
| Over 18.30 m up to 30 m | 1.33 + 0.73 + 0.64 = 2.7 | 1.0 + 0.5 + 0.9 = 2.4 |
| Over 30 m | 1.33 + 0.84 + 0.83 = 3.0 | 1.0 + 0.5 + 1.0 = 2.5 |
Common mistakes
- Using the gross plot area when the rules deduct road-widening, reservations or set-backs first.
- Treating FSI as carpet area. FSI counts built-up area; flats sold from it have a smaller carpet area — see the carpet area calculator.
- Forgetting that ground coverage, height limits, open-space rules and fire norms can stop you using the full FSI.
- Mixing units: convert acres, guntha or sq yd first with the area converter.
FSI Calculator FAQ
How do I calculate FSI?
Divide the total built-up floor area of all floors by the plot area. A 2,200 sq ft house on a 1,100 sq ft plot has an FSI of 2.0. The FSI calculator does it for a list of floors and subtracts any areas your rules exempt.
How much can I build with FSI 1.5?
Multiply the plot area by 1.5. On a 1,200 sq ft plot that is 1,800 sq ft of built-up area, before any exempt areas such as staircases that your local rules allow on top.
What is the FSI in Mumbai?
Under DCPR 2034 as sanctioned in 2018, the basic FSI is 1.33 in the Island City and 1.0 in the suburbs; with premium FSI and TDR the permissible FSI rises with road width up to 3.0 and 2.5. Check the current regulations and any special scheme for your plot.
Is FAR the same as FSI?
Yes — floor area ratio and floor space index are the same ratio. Some tables write FAR as a percentage (200 instead of 2.0) and New South Wales writes floor space ratio as 2:1.
What is TDR in FSI?
Transferable development rights are development rights granted elsewhere (for example for giving up land for a road) that can be loaded onto another plot, up to the limit the regulations allow, adding to its FSI.
Does this FSI calculator work for NSW floor space ratio?
Yes. Enter the site area and the maximum FSR from your council’s LEP map as the base FSI, or list gross floor areas in design mode to check a proposal.