Glossary
Plain-language definitions for the finance, economics, business, tax, and statistics terms used across our calculators. Every term below is tied to the specific calculator that puts it to work — click through to see it calculated, not just defined.
Written and maintained by Jay Sudha · Last reviewed 22 August 2026
Economics
Consumer Surplus
Consumer surplus is the difference between the maximum price a buyer is willing to pay for a unit of a good and the price they actually pay. On a supply-and-demand graph, it is the area between the demand curve and the market price, up to the quantity traded. It measures the value buyers capture from a market beyond what they spent.
See it in the Consumer Surplus CalculatorProducer Surplus
Producer surplus is the difference between the price a seller actually receives for a good and the minimum price they would have been willing to accept. On a supply-and-demand graph, it is the area between the supply curve and the market price, up to the quantity traded — the value sellers capture beyond their minimum acceptable price.
See it in the Producer Surplus CalculatorDeadweight Loss
Deadweight loss is the loss of total economic surplus (consumer plus producer surplus) that occurs when a market does not reach its efficient equilibrium quantity — typically because of a tax, subsidy, price ceiling, price floor, or quota. It represents value that neither buyers, sellers, nor the government capture; it is simply lost.
See it in the Deadweight Loss CalculatorMarket Equilibrium
Market equilibrium is the point where a market’s supply curve and demand curve intersect — the price (P*) and quantity (Q*) at which the quantity demanded equals the quantity supplied, with no shortage or surplus. Left alone, competitive markets tend toward this point.
See it in the Market Equilibrium CalculatorOpportunity Cost
Opportunity cost is the value of the best alternative forgone when a choice is made. It includes not just direct (explicit) cash costs but implicit costs like foregone income or investment returns — the full economic cost of picking one option instead of the next-best one.
See it in the Opportunity Cost CalculatorComparative Advantage
Comparative advantage is the ability to produce a good at a lower opportunity cost than another producer, even if that producer is more efficient at everything (absolute advantage). Two parties can both gain by specializing in what they have a comparative advantage in and trading — the foundation of trade theory.
See it in the Comparative Advantage CalculatorDiminishing Returns
Diminishing (marginal) returns describes a production process where, holding other inputs fixed, each additional unit of a variable input eventually adds less extra output than the unit before it. It does not mean output falls — just that its growth slows, before eventually turning negative if the input keeps increasing.
See it in the Diminishing Returns CalculatorMarginal Utility
Marginal utility is the additional satisfaction, or utility, a person gets from consuming one more unit of a good or service. It typically decreases as consumption increases (diminishing marginal utility) — the tenth slice of pizza adds less enjoyment than the first.
See it in the Marginal Utility CalculatorBusiness
Price Elasticity of Demand
Price elasticity of demand (PED) measures how sensitive the quantity demanded of a good is to a change in its price, usually calculated as the percentage change in quantity divided by the percentage change in price. Demand is "elastic" when a price change causes a proportionally larger change in quantity, and "inelastic" when it causes a smaller one.
See it in the Price Elasticity of Demand CalculatorMarkup
Markup is the amount added on top of a product’s cost to arrive at its selling price, expressed as a percentage of the cost (not the price — that’s margin). A $10 cost item sold for $15 has a 50% markup, even though its profit margin is only 33%. The two are often confused despite describing different things.
See it in the Markup CalculatorProfit Margin
Profit margin is profit expressed as a percentage of revenue, not cost — gross margin uses gross profit (revenue minus cost of goods sold), while net margin accounts for all expenses. It is a measure of pricing power and cost control, and is easy to confuse with markup, which uses cost as its base instead of revenue.
See it in the Profit Margin CalculatorBreak-Even Point
The break-even point is the level of sales (in units or revenue) at which total revenue equals total costs, so profit is exactly zero. It is calculated by dividing fixed costs by the contribution margin per unit (price minus variable cost). Sales beyond that point generate profit; sales below it generate a loss.
See it in the Break-Even CalculatorROAS (Return on Ad Spend)
ROAS (return on ad spend) is the revenue generated per dollar of advertising spend, usually shown as a ratio (e.g. 4:1) or a percentage. It differs from ROI because it looks only at revenue against ad spend, not profit against total investment — a high ROAS can still be unprofitable if margins are thin.
See it in the Break-Even ROAS CalculatorLTV:CAC Ratio
The LTV:CAC ratio compares customer lifetime value (LTV) — the total profit a customer generates over the time they stay — with customer acquisition cost (CAC), what it cost in sales and marketing to win them. A ratio of 3:1 or higher is a common (though rough) rule of thumb for a healthy, sustainable growth model.
See it in the LTV:CAC CalculatorFinance
Amortization
Amortization is the process of paying off a loan through scheduled, usually equal, payments over time. Each payment covers that period’s interest first, with the remainder reducing the principal balance — so early payments are interest-heavy and later payments are principal-heavy, even though the payment amount stays the same.
See it in the Amortization CalculatorAPR (Annual Percentage Rate)
APR (annual percentage rate) expresses the total yearly cost of a loan, combining the nominal interest rate with most upfront and financed fees, spread over the loan term. Because it folds fees into a single rate, APR is generally a better way to compare two loan offers than comparing their interest rates alone.
See it in the APR CalculatorDebt-to-Income Ratio
Debt-to-income ratio (DTI) is total monthly debt payments divided by gross monthly income, expressed as a percentage. Mortgage lenders use it to gauge how much additional debt a borrower can reasonably take on — most conventional loan programs look for a DTI at or below roughly 36–43%, though limits vary by lender and loan type.
See it in the Mortgage CalculatorRefinance Break-Even Point
The refinance break-even point is the number of months it takes for the monthly payment savings from a mortgage refinance to add up to more than the closing costs paid to get the new loan. Refinancing tends to make sense only if you plan to stay in the home well past that point.
See it in the Mortgage Refinance CalculatorCompound Interest
Compound interest is interest calculated on a balance that includes both the original principal and any interest already added to it — so the balance grows faster over time than it would under simple interest, which only ever applies to the original principal. How often it compounds (daily, monthly, annually) affects how fast it grows.
See it in the Compound Interest CalculatorInvesting
Dividend Reinvestment (DRIP)
Dividend reinvestment (often called a DRIP, dividend reinvestment plan) is the practice of automatically using cash dividends to purchase additional shares of the same investment, rather than receiving the dividend as cash. Over long periods this compounds an investor’s share count and, with it, future dividend income.
See it in the Dividend Reinvestment CalculatorCash-on-Cash Return
Cash-on-cash return measures the annual pre-tax cash flow a real estate investment generates, divided by the actual cash invested (typically the down payment, closing costs, and any renovation spend) — not the full property value. It shows the return on the cash you actually put in, separate from returns driven by appreciation or loan paydown.
See it in the Real Estate Investment CalculatorROI (Return on Investment)
ROI (return on investment) measures the gain or loss from an investment relative to its cost, usually as a percentage: (final value minus initial investment) divided by initial investment. Annualized ROI converts a total return over any holding period into an equivalent yearly rate, making investments of different lengths comparable.
See it in the ROI CalculatorMath & Statistics
Standard Deviation
Standard deviation measures how much the values in a dataset typically differ from the mean. A small standard deviation means values cluster tightly around the average; a large one means they are spread widely. Sample standard deviation (dividing by n−1) is used when your data is a subset of a larger population; population standard deviation (dividing by N) is used when it is the entire population.
See it in the Standard Deviation CalculatorTax
VAT (Value Added Tax)
VAT (value added tax) is a consumption tax applied at each stage of a product’s production and distribution, based on the value added at that stage. Businesses collect it on sales and reclaim it on their own purchases, so it is economically borne by the final consumer, similar in effect to GST or sales tax used elsewhere.
See it in the VAT/GST CalculatorEffective Tax Rate
Effective tax rate is total tax paid divided by total taxable income, expressed as a percentage. It is different from the marginal tax rate (your top bracket), because most tax systems apply lower rates to earlier portions of income — so the effective rate is a blended average, always at or below the marginal rate.
See it in the Income Tax CalculatorGross-to-Net Pay
Gross-to-net pay is the calculation that takes gross pay — salary or wages before anything is withheld — and subtracts taxes, social insurance contributions, and other deductions to arrive at net (take-home) pay, the amount actually deposited into a paycheck.
See it in the Take-Home Pay CalculatorDefinitions are educational and written to match how each linked calculator uses the term. They are not financial, tax, legal, investment, or professional advice. See our methodology for how our calculators and content are built and reviewed.