Calculator & Finance Glossary
Every calculator assumes you know a few key terms. Here they are in plain English, grouped by field. On most tool pages on this site, underlined dotted terms show the same definitions on hover.
Loans & Borrowing
| Term | Meaning |
|---|---|
| APR | Annual Percentage Rate — the yearly cost of a loan, including fees, expressed as one percentage. Lower APR usually means a cheaper loan, but compare like-for-like terms. |
| EMI | Equated Monthly Installment — the fixed payment a borrower makes each month. See the Loan EMI Calculator. |
| Principal | The original amount borrowed or invested, before any interest. |
| Amortization | Paying off debt through regular payments; early payments are mostly interest, later ones mostly principal. |
| Simple Interest | Interest calculated only on the principal: Principal × Rate × Time. |
| Compound Interest | Interest on interest — interest is added to the principal, so the base keeps growing. See the compound interest guide. |
| LTV | Loan-to-Value ratio — loan ÷ property value. Above 80% often triggers mortgage insurance. |
| DTI | Debt-to-Income ratio — monthly debt payments ÷ gross monthly income. Lenders use it to judge affordability. |
| YTM | Yield to Maturity — the total return expected if a bond is held until it matures. |
Investing & Property
| Term | Meaning |
|---|---|
| NPV | Net Present Value — today's value of future cash flows minus today's cost. Positive NPV generally means a project adds value. |
| IRR | Internal Rate of Return — the discount rate at which NPV becomes zero; handy for comparing investments. |
| ROI | Return on Investment — profit ÷ cost, as a percentage. |
| CAGR | Compound Annual Growth Rate — the smoothed yearly growth rate over a period, ignoring ups and downs in between. |
| Cap Rate | Capitalization Rate — net operating income ÷ property value, used to compare rental properties. |
Health & Fitness
| Term | Meaning |
|---|---|
| BMI | Body Mass Index — weight ÷ height², a population-level screening number, not a body-fat measurement. See the BMI guide. |
| BMR | Basal Metabolic Rate — calories your body burns at complete rest. |
| TDEE | Total Daily Energy Expenditure — BMR plus all activity; the number to match for weight maintenance. |
| VO2 Max | The maximum oxygen your body can use during intense exercise — a key fitness indicator. |
| BSA | Body Surface Area — used in medical dosing and burn assessment. |
Statistics
| Term | Meaning |
|---|---|
| Standard Deviation | How spread out numbers are around the mean; small = values cluster tightly. |
| Variance | The square of standard deviation — the average of squared differences from the mean. |
| Median | The middle value of sorted data; less distorted by outliers than the average. |
| Percentile | The value below which a given percentage of data falls — 90th percentile means 90% of values are lower. |
Math Essentials
| Term | Meaning |
|---|---|
| GCD | Greatest Common Divisor — the largest whole number that divides both numbers exactly. |
| LCM | Least Common Multiple — the smallest number both numbers divide into. |
| Determinant | A single number computed from a square matrix; non-zero means the matrix is invertible. |
| Logarithm | The inverse of exponentiation — log₂8 = 3 because 2³ = 8. |
| Factorial | The product of all positive integers up to n, written n! — 5! = 120. |
| Permutation | An arrangement where order matters (ABC ≠ CAB). |
| Combination | A selection where order doesn't matter (ABC = CAB). |
| Modulo | The remainder after division — 17 mod 5 = 2. |
| Complex Number | A number with real and imaginary parts, written a + bi. |
| Quadratic Equation | ax² + bx + c = 0, solved with the quadratic formula. |
| Discriminant | b² − 4ac; positive = two real roots, zero = one repeated root, negative = no real roots. |
| Heron's Formula | Triangle area from its three sides: √(s(s−a)(s−b)(s−c)) where s = (a+b+c)/2. |
| Pythagorean Theorem | In a right triangle, a² + b² = c², where c is the hypotenuse. |
Using terms with the calculators
These definitions match the tooltips embedded across our tool pages. If a term on a calculator page confuses you, search this page with your browser (Ctrl+F) — each definition is written to stand on its own.
Worked example: Loan EMI Calculator at its default inputs
Open Loan EMI Calculator and press calculate without editing a field. What comes back is the table and result below, so the glossary numbers here are checkable in one click.
| Input | Default |
|---|---|
| Loan Amount | 100000 |
| Interest Rate (% per year) | 8.5 |
| Loan Term (years) | 5 |
| Payment per Period (for solve modes) | 2000 |
| Interest-Only Period (years) | 2 |
Result: Payment: $2,051.65 / monthly
The steps behind that answer
- Solving for Payment (DCC: Actual/365)
- Step 1: Rate per monthly = 8.5% → 0.7083% (Actual/365)
- Step 2: Periods n = 5×12 = 60
- Step 3: PMT = P×r×(1+r)^n / ((1+r)^n − 1)
Loan Amount: half, as given, and half again
Same calculator, same fields, one change: loan amount.
| Loan Amount | Result |
|---|---|
| 50,000 | Payment: $1,025.83 / monthly |
| 100,000 | Payment: $2,051.65 / monthly |
| 150,000 | Payment: $3,077.48 / monthly |
Halve loan amount and the result moves one way; add half again and it moves the other. Watching that gap is quicker than guessing which field matters most.
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