Calculator Glossary
Plain-spoken definitions of the finance, math, health, business, and construction terms used across the calculators. Terms that power a tool link straight to it.
Finance ›
- Amortization
- Spreading a loan into fixed payments over time, each covering interest plus a portion of principal. An amortization schedule shows the month-by-month split.
- APR tool ›
- Annual Percentage Rate: the yearly cost of borrowing including interest and most fees, expressed as a percentage. Compare loans by APR, not just the interest rate.
- Principal
- The original amount borrowed, before interest. Your monthly payment reduces principal once accrued interest is covered.
- Extra payment tool ›
- An additional amount paid toward a loan beyond the scheduled monthly payment. Applied to principal, it shortens the term and cuts total interest.
- Payoff date tool ›
- The date a loan reaches zero balance, given current payments. Extra payments move it earlier.
- Sales tax tool ›
- A consumption tax added to the price of goods and services, set by state and often local governments.
- Gross pay tool ›
- Total earnings before any deductions like taxes, insurance, or retirement contributions.
- Net pay
- Take-home earnings after deductions are removed from gross pay.
- Lease tool ›
- Renting a car for a fixed term and mileage allowance instead of financing its full purchase.
- Residual value
- A car's estimated worth at the end of a lease; it determines lease payments and your buyout price.
- Income shares tool ›
- A child support model that combines both parents' incomes and apportions support by their relative share.
- Refinance tool ›
- Replacing a loan with a new one at different terms or rate, often to lower monthly payments or total interest.
- Net worth tool ›
- Total assets minus total liabilities; the single summary of your financial position.
- CAGR tool ›
- Compound annual growth rate: the steady annual return that produces a given ending value, used to compare investments fairly.
- Snowball / avalanche tool ›
- Two credit-card payoff strategies: smallest-balance-first for motivation, or highest-APR-first to minimize interest.
- Cap rate tool ›
- Capitalization rate: net operating income divided by property price, a measure of a rental's unlevered return.
- Markup tool ›
- Profit as a percentage of cost, used to set selling prices (distinct from margin, which is a percentage of price).
- Margin
- Profit as a percentage of the selling price; the number most retailers quote, always smaller than the equivalent markup.
Math ›
- Percentage tool ›
- A fraction of 100. 25% means 25 parts out of 100, or 0.25.
- Percent change tool ›
- How much a value increased or decreased relative to its starting point, expressed as a percentage.
- Hypotenuse tool ›
- The longest side of a right triangle, opposite the right angle.
- Pythagorean theorem tool ›
- In a right triangle, the square of the hypotenuse equals the sum of the squares of the other two sides.
- Leg tool ›
- Either of the two shorter sides of a right triangle that form the right angle.
- Unit tool ›
- A standard of measurement such as meter, pound, or Celsius degree.
- Metric system tool ›
- The decimal system of measurement based on the meter, kilogram, and liter.
- Imperial system tool ›
- The measurement system using feet, pounds, and Fahrenheit, common in the US.
- Discriminant tool ›
- In ax² + bx + c, the value b² − 4ac that predicts whether roots are real, double, or complex.
- Standard deviation tool ›
- A measure of how spread out numbers are around their mean; low means clustered, high means scattered.
- Scientific notation tool ›
- Writing a number as a coefficient between 1 and 10 times a power of ten, e.g. 1.5 × 10⁸.
- GCD tool ›
- Greatest common divisor: the largest number dividing a set of numbers evenly.
- LCM tool ›
- Least common multiple: the smallest number a set of numbers all divide into evenly.
- Logarithm tool ›
- The power a base must be raised to produce a given number; log₁₀(1000) = 3.
- Roman numeral tool ›
- The numeral system using I, V, X, L, C, D, M with subtractive notation (IV = 4).
- Hexadecimal tool ›
- Base-16 notation using 0-9 and A-F; a compact shorthand for binary, one hex digit per four bits.
- Median tool ›
- The middle value of a sorted list; robust to outliers compared to the mean.
- Mode tool ›
- The most frequently occurring value in a data set.
Health & Fitness ›
- TDEE tool ›
- Total Daily Energy Expenditure: the calories you burn in a day, including activity. Eat near it to maintain weight.
- BMR tool ›
- Basal Metabolic Rate: the calories your body burns at complete rest just to stay alive.
- BMI tool ›
- Body Mass Index: a height-to-weight ratio used to screen weight categories.
- Calorie deficit
- Eating fewer calories than your TDEE so the body uses stored energy; the usual lever for weight loss.
- Macros tool ›
- Macronutrients: protein, fat, and carbohydrates, the three nutrients your body needs in large amounts.
- Mifflin-St Jeor tool ›
- A formula that estimates BMR from age, sex, height, and weight, often preferred for its accuracy.
- Maintenance calories tool ›
- The calorie intake that keeps your weight steady at your current activity level.
- Lean body mass tool ›
- Total weight minus fat mass: muscle, bone, organs, and water, the metabolically active tissue.
- FFMI tool ›
- Fat-free mass index: lean body mass per square metre of height, normalising muscle to body size.
- Waist-to-hip ratio tool ›
- Waist circumference divided by hip circumference; a measure of abdominal fat distribution.
- Karvonen method tool ›
- Computing training zones from heart-rate reserve (max minus resting), personalising zones to fitness.
- 1RM tool ›
- One-rep max: the maximum weight lifted for a single rep, often estimated from a multi-rep set.
- Ovulation tool ›
- The release of an egg mid-cycle; roughly 14 days before the next period, marking peak fertility.
Business ›
- Invoice tool ›
- A document listing goods or services provided, their prices, and the amount due.
- Line item
- A single row on an invoice describing one product or service with its quantity and rate.
- Tax rate tool ›
- The percentage applied to a taxable amount to calculate the tax owed.
- Logo
- A graphic mark identifying a business, used on branded documents like invoices.
- ROI tool ›
- Return on investment: total gain divided by total invested, expressed as a percentage.
- Freelance rate tool ›
- The hourly charge a freelancer sets to cover income, expenses, tax, and non-billable time.
- Billable hours tool ›
- Hours charged to clients, as opposed to admin, quoting, and marketing time.
- Hex code tool ›
- A #RRGGBB colour code used in web design, e.g. #FF8800 for a bright orange.
- Business day tool ›
- A weekday (Monday–Friday), used for deadlines, delivery, and payment terms.
Home & Construction ›
- Roof pitch tool ›
- The steepness of a roof, usually expressed as inches of rise per 12 inches of run.
- Square (roofing)
- A roofing measurement equal to 100 square feet of roof surface; materials are quoted per square.
- Asphalt shingle tool ›
- The most common roofing material: fiberglass base coated with asphalt and granules.
- Underlayment
- A protective layer between the roof deck and the roofing material.
- Board foot tool ›
- A lumber volume unit equal to 1 inch × 12 inches × 1 foot (thickness × width × length ÷ 12).
- Cubic yard tool ›
- 27 cubic feet; the standard unit for ordering concrete, mulch, and gravel in bulk.
- Slope factor tool ›
- The ratio of sloped roof area to flat footprint; multiply footprint by it to get true surface area.
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