Glossary
Plain-English definitions of the terms our calculators use, each linking to the tool where you can put it to work.
- Amortization
- Paying off a loan with regular payments that each cover the interest due plus part of the principal. Early payments are mostly interest; late payments are mostly principal. The full month-by-month table is an amortization schedule. Try the Amortization Calculator →
- APR (Annual Percentage Rate)
- The yearly cost of borrowing including interest and most fees, expressed as a percentage. Two loans with the same interest rate can have different APRs because of fees — compare loans by APR, not the headline rate. Try the Loan Calculator →
- APY (Annual Percentage Yield)
- The yearly return on savings once compounding is included. A 5% rate compounded monthly gives about 5.12% APY. Banks quote APY on savings because compounding makes it slightly higher than the rate. Try the Compound Interest Calculator →
- BMI (Body Mass Index)
- Weight in kilograms divided by height in metres squared. A quick screening number: 18.5–24.9 is the standard healthy range. It cannot distinguish muscle from fat, so athletes often read high. Try the BMI Calculator →
- BMR (Basal Metabolic Rate)
- The calories your body burns at complete rest, just running its basic functions. It is the floor of your energy needs — daily calorie targets are built on top of it. Try the BMR Calculator →
- Body fat percentage
- The share of your body weight that is fat tissue. More informative than BMI for tracking fitness, since it separates fat from muscle. Try the Body Fat Calculator →
- Calorie deficit
- Eating fewer calories than you burn. A sustained deficit of about 500 kcal/day produces roughly 0.5 kg (1 lb) of weight loss per week. Try the Weight Loss Planner →
- Compound interest
- Interest calculated on the balance including previously earned interest — interest on interest. It makes savings grow on a steepening curve and makes unpaid debt grow the same way. Try the Compound Interest Calculator →
- Down payment
- The upfront cash portion of a purchase price, with the rest financed by a loan. A larger down payment means a smaller loan, lower monthly payments, and often a better rate. Try the Mortgage Calculator →
- Equity (home)
- The part of your home you actually own: current market value minus what you still owe on the mortgage. It grows as you repay principal and as the property appreciates. Try the Home Equity Calculator →
- GPA (Grade Point Average)
- The average of your grades converted to a point scale (commonly 4.0), weighted by course credits. A weighted GPA also rewards harder courses with bonus points. Try the GPA Calculator →
- Gross vs net pay
- Gross pay is your salary before deductions; net pay (take-home) is what remains after tax, social contributions and other deductions. Negotiate in gross, budget in net. Try the Salary Calculator →
- Inflation
- The general rise in prices over time, which shrinks what each unit of money can buy. At 3% inflation, today's $100 buys only about $74 worth of goods in ten years. Try the Inflation Calculator →
- kWh (kilowatt-hour)
- The unit electricity is billed in: one kilowatt of power used for one hour. A 100 W device running 10 hours uses 1 kWh. Try the Electricity Cost Calculator →
- Logarithm
- The inverse of exponentiation: log_b(x) asks "b to what power gives x?". log₁₀(1000) = 3. Natural log (ln) uses the constant e ≈ 2.718. Try the Logarithm Calculator →
- Macros (macronutrients)
- The three nutrients that supply calories: protein (4 kcal/g), carbohydrates (4 kcal/g) and fat (9 kcal/g). A macro split divides your calorie target among them. Try the Macro Calculator →
- Markup vs margin
- Markup is profit as a percentage of cost; margin is profit as a percentage of the selling price. A 50% markup equals a 33% margin — mixing them up misprices products. Try the Percentage Calculator →
- Mean, median & mode
- Three kinds of "average": the mean (sum ÷ count), the median (middle value when sorted, resistant to outliers) and the mode (most frequent value). Try the Average Calculator →
- Percentage
- A fraction expressed out of 100. "X% of Y" is (X ÷ 100) × Y. Percentage change is (new − old) ÷ old × 100. Try the Percentage Calculator →
- Principal
- The original amount borrowed or invested, before interest. On a loan, every payment splits between interest (the cost) and principal (actually reducing what you owe). Try the Loan Calculator →
- Quadratic equation
- An equation of the form ax² + bx + c = 0, solved with the quadratic formula x = (−b ± √(b²−4ac)) ÷ 2a. The discriminant b²−4ac tells you how many real solutions exist. Try the Quadratic Equation Solver →
- ROI (Return on Investment)
- Profit as a percentage of the amount invested: (gain − cost) ÷ cost × 100. A $1,000 investment that grows to $1,150 has a 15% ROI. Try the Investment Calculator →
- Sales tax / VAT
- A percentage added to a purchase price at checkout (sales tax) or built into the displayed price (VAT). Reverse-calculating it tells you the pre-tax price from a total. Try the Sales Tax Calculator →
- Standard deviation
- A measure of how spread out numbers are around their average. Low means the values cluster tightly; high means they vary widely. In a normal distribution about 68% of values fall within one standard deviation of the mean. Try the Standard Deviation Calculator →
- TDEE (Total Daily Energy Expenditure)
- Your total calories burned per day: BMR plus all activity. Eating below TDEE loses weight; above it gains. Most diet math starts here. Try the Calorie Calculator (TDEE) →
- Unit price
- Price divided by quantity — cost per kilogram, per litre, per item. The only fair way to compare package sizes at the store; the bigger pack is not always cheaper. Try the Unit Price Calculator →
- VO₂ max
- The maximum rate at which your body can use oxygen during exercise — the standard measure of aerobic fitness. Higher is fitter; it improves with endurance training. Try the VO2 Max Calculator →
- Waist-to-height ratio
- Waist circumference divided by height. Keeping it under 0.5 ("waist less than half your height") is a simple, well-supported health guideline. Try the Waist-to-Height Ratio Calculator →
- Weighted average
- An average where some values count more than others. Course grades are the classic case: a final worth 40% moves your grade four times as much as a quiz worth 10%. Try the Weighted Grade Calculator →