Mathematical & Financial Formula Hub

Unit Converters

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Pounds to Kilograms Formula

$$\text{Kilograms (kg)} = \text{Pounds (lbs)} \times 0.45359237$$

One international avoirdupois pound is legally defined as exactly 0.45359237 kilograms. To convert pounds to kilograms, multiply the mass in pounds by 0.45359237 (or divide by 2.20462262).

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Finance

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PPF Formula

$$F = P \times \frac{(1 + r)^n - 1}{r} \times (1 + r)$$

The Public Provident Fund (PPF) is a popular long-term savings-cum-tax-saving instrument in India. It offers guaranteed interest rates set quarterly by the government, with tax-free returns and tax deductions under Section 80C.

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Health

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Pregnancy Due Date Formula

$$\text{Due Date} = \text{Last Menstrual Period} + 280 \text{ days} + (\text{Cycle Length} - 28)$$

Naegele's Rule estimates a pregnancy due date by adding 280 days (40 weeks) to the first day of the last menstrual period, since gestational age is conventionally measured from LMP even though conception typically occurs about two weeks later. A cycle-length adjustment corrects for women whose cycles are longer or shorter than the standard 28-day assumption, since a longer cycle means ovulation (and conception) happens later.

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Finance

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Profit Margin & Markup Formula

$$\text{Gross Margin (\%)} = \frac{\text{Revenue} - \text{COGS}}{\text{Revenue}} \times 100, \quad \text{Markup (\%)} = \frac{\text{Revenue} - \text{COGS}}{\text{COGS}} \times 100$$

Profit margin evaluates profitability as a percentage of total selling revenue, while cost markup calculates profit as a percentage of purchase/production cost.

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Real Estate

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Property Cost Formula

$$\text{Total Cost} = P + P\left(\frac{\text{GST}+\text{Stamp Duty}+\text{Registration}+\text{Brokerage}}{100}\right) + \text{Other Charges}$$

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.

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Real Estate

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Property ROI Formula

$$\begin{aligned} \text{Total Profit} &= (\text{Current Value} - \text{Purchase Price}) + (\text{Net Annual Rent} \times \text{Years Held}) \\ \text{Annualized ROI} &= \left[\left(1 + \frac{\text{Total Profit}}{\text{Total Investment}}\right)^{1/\text{Years}} - 1\right] \times 100 \end{aligned}$$

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.

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Health

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Protein Intake Formula

$$\text{Protein Target (g)} = \text{Body Weight (kg)} \times \text{Multiplier(Goal, Activity)} + \text{Adjustments}$$

Rather than using a single flat RDA figure (0.8 g/kg), this formula applies an evidence-informed multiplier that varies by both fitness goal and activity level, since athletic, weight-loss, and muscle-building populations need substantially more protein than a sedentary baseline to preserve or build lean mass. Additional flat or incremental bonuses account for higher protein needs in older adults and during pregnancy/lactation.

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Mathematics & Education

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Ratio & Proportion Formula

$$\text{Share}_A = \text{Total} \times \left(\frac{A}{A + B + C}\right)$$

Ratio and proportion formulas divide a total quantity into proportional parts based on specified ratio terms or test equality between two fractions (a/b = c/d).

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Finance

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RD Formula

$$M = \sum_{i=1}^{k} P \times \left(1 + \frac{r}{4}\right)^{4 \times \frac{k - i + 1}{12}}$$

A Recurring Deposit (RD) is a savings tool that allows individuals to deposit a fixed sum monthly for a predefined period. Similar to a Fixed Deposit, it offers a guaranteed rate of interest, usually compounded quarterly, but without requiring a large initial lump sum.

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Real Estate

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Rent vs Buy Formula

$$\begin{aligned} \text{Buyer Net Wealth} &= \text{Home Equity} + \text{Invested Cash Surplus} \\ \text{Renter Net Wealth} &= \text{Invested Down Payment} + \text{Invested Cash Surplus} \end{aligned}$$

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.

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