Mathematical & Financial Formula Hub
Peer-verified equations, variable definitions, and step-by-step worked calculations for online tools.
Built-Up Area Formula
Built-Up Area adds the thickness of walls and any balcony space to the Carpet Area, representing a unit's full physical footprint. Since most listings and price quotes reference Built-Up (or Super Built-Up) Area rather than Carpet Area, this formula helps buyers convert between the two to estimate real usable space or verify a quoted built-up figure.
Carpet Area Formula
Carpet Area, Built-Up Area, and Super Built-Up Area are the three RERA-defined area measures used across Indian real estate listings. Carpet Area is the actual usable floor space within the walls of a unit, while Super Built-Up Area — the figure most often quoted in pricing — adds walls, balconies, and a proportionate share of shared building amenities. This formula lets a buyer work backward from the quoted saleable area to the real usable space.
Home Loan Eligibility Formula
Banks use the Fixed Obligation to Income Ratio (FOIR) method to decide how much of your monthly income can go toward loan repayments. The FOIR percentage itself rises with income (40% for lower incomes up to 55% for higher earners), reflecting that higher earners can comfortably commit more of their salary. Once the maximum affordable EMI is known, the eligible loan amount is reverse-calculated using the standard loan annuity formula.
Property Cost Formula
The advertised price of a property is rarely the full cost of buying it. Government taxes (GST, stamp duty, registration) and transaction costs (brokerage) are each calculated as a percentage of the base price and added on top, along with flat one-time charges, to reveal the true out-of-pocket cost a buyer must budget for.
Property ROI Formula
Property ROI combines two sources of return — capital appreciation (the rise in property value) and rental income (cash flow after expenses) — and expresses the combined profit as a percentage of the actual cash invested. The annualized version converts multi-year total returns into a CAGR-equivalent figure so property returns can be fairly compared against other investments like stocks or mutual funds.
Rent vs Buy Formula
This is a year-by-year wealth simulation rather than a single formula: each year, the buyer's wealth grows through mortgage principal repayment (building equity) plus property appreciation, while the renter's wealth grows by investing the money they would have spent on a down payment plus any monthly savings versus the buyer's EMI and upkeep costs. Comparing the two paths at the end of a chosen holding period, and finding the year they cross over, reveals which option builds more net wealth.
Rental Yield Formula
Gross rental yield gives a quick headline return relative to purchase price, but ignores costs. Net rental yield deducts expected vacancy losses and all recurring ownership expenses (maintenance, tax, insurance) to reveal the real cash yield a landlord actually earns — the standard, more reliable metric for judging whether a rental property is a good income investment.
Super Built-Up Area Formula
Super Built-Up Area — often called "saleable area" — is the figure developers actually price and sell against. It adds a "loading" percentage on top of the Built-Up Area to account for the buyer's proportionate share of shared building amenities, so understanding the loading factor helps a buyer see how much of the quoted price is for their own flat versus common spaces.
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