What the calculator does

It performs one calculation: it multiplies the plot area you enter by the floor area ratio you enter, twice, and subtracts one result from the other.

The output is the additional floor area implied by the gap between the two ratios you supplied. That arithmetic is exact and you can check it by hand; the page shows the formula for that reason.

What it is not

These four limits are stated on the calculator itself and are repeated here because they are the whole of the matter:

• It is not a Development Rights Certificate quantity. The relationship between additional floor area and the certificate entitlement required is set by the authority's rules. Treating the output as a quantity to acquire would be a serious error.
• It is not a permission. It cannot tell you whether additional floor area may be used on your site. Zone, site conditions and the authority decide that.
• It is not an eligibility check. It says nothing about whether any certificate, or your project, qualifies for anything.
• It is not a price, a valuation or an indication of cost. No value, percentage or market price is implied.

The figures are yours

The calculator does not know your site. The plot area and both floor area ratios are values you type in, and it does not verify, validate or source any of them. The permissible ratio for a site is determined by the applicable regulations and the authority, and is not something this tool can look up or confirm.

An exact calculation performed on an incorrect input produces an incorrect result that looks entirely authoritative. That risk sits with the figures, not with the arithmetic.

Do not rely on it for a decision

The output is indicative only, intended to frame a conversation. It must not be relied upon for eligibility, valuation, design, financing, acquisition or approval decisions.

Eligibility, quantity, transfer and utilisation are determined by the competent planning authority in each case. Nothing on this site is, or substitutes for, that determination.

Take your own professional advice and confirm the position with the competent authority before acting.