Every calculator on this site assumes you already know what it is calculating. This page fills that gap. Each entry defines a term in plain language, at most two paragraphs, and links to the tool that puts it to work. The terms are grouped by the field they come from.
Finance and business
Margin vs. markup
Both describe profit, but against different bases. Margin is profit as a share of the selling price; markup is profit as a share of the cost. Buy for $80, sell for $100, and the $20 profit is a 20% margin but a 25% markup. Because the denominators differ, the two numbers drift apart as they grow, and quoting one when you mean the other is a common pricing mistake.
Use margin when you are thinking about revenue and markup when you are setting a price from a known cost. The margin calculator shows both from the same inputs so the difference is explicit.
Loan-to-value (LTV)
LTV is the loan amount divided by the value of the asset securing it, as a percentage. A $180,000 mortgage on a $200,000 home is 90% LTV. Lenders read it as risk: the higher the LTV, the less owner equity cushions a drop in value, which is why rates and mortgage insurance requirements often step up past 80%.
See the LTV calculator to convert between loan amount, value, and ratio.
Debt service coverage ratio (DSCR)
DSCR is net operating income divided by total debt service (principal plus interest) over the same period. A DSCR of 1.25 means income covers the debt payment 1.25 times over. Below 1.0, the property does not earn enough to pay its own loan; commercial and rental lenders usually want a comfortable margin above 1.0.
The DSCR loan calculator works the ratio from income and payment.
Capitalization rate (cap rate)
A cap rate is a property's net operating income divided by its price, expressed as a percentage — the unleveraged yield if you paid cash. It lets you compare properties of different sizes on the same footing. A lower cap rate usually reflects a higher price for a given income, which the market tends to assign to assets it sees as safer or better located.
Compute it either direction with the cap rate calculator.
Break-even point
The break-even point is the sales volume at which total revenue equals total cost, so profit is zero. Below it you lose money, above it you make money. It is found by dividing fixed costs by the contribution margin per unit — the price minus the variable cost of each unit.
The break-even calculator turns fixed cost, price, and unit cost into that volume.
CD early withdrawal penalty
A certificate of deposit locks money for a fixed term in exchange for a set rate. Take it out early and the bank charges a penalty, usually stated as a number of months of interest — for example, 90 days of interest on a short CD or 180 days on a longer one. The penalty can eat into principal if you withdraw before enough interest has accrued to cover it.
The CD calculator shows the penalty and what you actually walk away with.
HELOC
A home equity line of credit is a revolving loan secured by the equity in your home. You draw from it as needed up to a limit during a draw period, paying interest only on what you use, then repay the balance over a later term. The rate is usually variable, tied to a benchmark plus a margin.
Estimate payments and available credit with the HELOC calculator.
Net promoter score (NPS)
NPS measures customer loyalty from a single question — how likely are you to recommend us, 0 to 10. Respondents scoring 9–10 are promoters, 7–8 are passives, and 0–6 are detractors. The score is the percentage of promoters minus the percentage of detractors, giving a number from −100 to +100. Passives count toward the total but not the score.
The NPS calculator works the score from response counts.
CPM (cost per mille)
CPM is the cost of one thousand impressions in advertising — "mille" is Latin for thousand. It is the price of reach, not of clicks or sales, and lets you compare the cost of showing an ad across campaigns of different sizes. Total cost divided by impressions, times a thousand.
Convert between cost, impressions, and CPM with the CPM calculator.
Work and pay
PTO accrual
Paid time off often builds up gradually rather than arriving in a lump each year. The accrual rate is how much PTO you earn per unit of work — for instance, a set number of hours per pay period or per hour worked. Multiply the rate by time worked to see the balance at any date.
The PTO accrual calculator projects the balance forward from a rate and a starting point.
Overtime and time and a half
In the United States, non-exempt employees earn overtime for hours worked beyond 40 in a week, paid at "time and a half" — 1.5 times the regular hourly rate. Some situations carry double time. The premium applies to the extra hours only, not to the whole week.
The overtime calculator splits regular and overtime pay from hours and rate.
Severance pay
Severance is compensation offered when employment ends, often expressed as a number of weeks of pay per year of service. It is not legally required in most of the United States; when it is offered, the formula and any conditions come from company policy or a negotiated agreement.
Estimate a package from tenure and salary with the severance calculator.
Construction and home
R-value
R-value measures a material's resistance to heat flow: the higher the number, the better it insulates. It depends on the material and its thickness together, so a thin sheet of rigid foam can out-insulate a thicker fiberglass batt. Recommended R-values for walls, attics, and floors vary by climate zone.
The R-value calculator helps size insulation to a target.
CFM (cubic feet per minute)
CFM is a measure of airflow — the volume of air a fan, vent, or HVAC system moves each minute. Sizing ventilation to a room means matching CFM to the room's volume and the number of air changes per hour the use calls for; a bathroom fan and a kitchen hood have very different targets.
Size airflow to a room with the CFM calculator.
Cubic yard
Concrete and bulk materials are sold by the cubic yard — a cube three feet on each side, or 27 cubic feet. Estimating a pour means converting the slab or footing's dimensions to cubic yards, then adding a small overage for spillage and uneven subgrade so you do not come up short mid-pour.
The concrete calculator converts dimensions to yards with an overage allowance.
Freight class
In US less-than-truckload shipping, freight class is a standardized code (from 50 to 500) that sets how a shipment is priced. It is derived mainly from density — weight per cubic foot — along with handling, stowability, and liability. A dense, sturdy pallet lands in a low class and ships cheaper per pound than a light, bulky one.
The freight class calculator derives the class from dimensions and weight.
Statistics
Standard deviation
Standard deviation measures how spread out a set of numbers is around their average: a small value means the data cluster tightly, a large one means they scatter widely. It is the square root of the variance, in the same units as the data itself, which is why it is the more readable of the two.
The sample version divides by n − 1 to correct for the bias of estimating a population from part of it; the population version, used when you have every data point, divides by n. The standard deviation calculator shows both side by side.
Health
A1C
The A1C test reports the share of hemoglobin in the blood that has glucose attached, as a percentage. Because red blood cells live about three months, it reflects average blood sugar over that window rather than a single moment. It is often translated into an estimated average glucose (eAG) in the same units as a home meter.
Convert between A1C and eAG with the A1C calculator. This is educational, not medical advice.
Creatinine clearance
Creatinine clearance estimates how well the kidneys filter waste, using serum creatinine together with age, weight, and sex — most commonly through the Cockcroft–Gault formula. It is an estimate of kidney function used to guide dosing and screening, not a direct measurement.
The creatinine clearance calculator applies the formula. It is educational, not medical advice.
Blood alcohol content (BAC)
BAC is the percentage of alcohol in the bloodstream. It rises with the number of drinks and falls slowly as the body metabolizes alcohol at a roughly fixed rate, and it is influenced by body weight, sex, and time. Estimates from a formula are approximate and never a substitute for a breathalyzer or for not driving.
The BAC calculator gives an estimate from drinks, weight, and time. It is educational, not a legal or medical determination.
A note on these definitions
Each entry is written to make a tool's output legible, not to replace professional judgment. Where money or health is involved, treat the number as a starting point and confirm it with someone who knows your specific situation.
Frequently asked questions
What is the difference between margin and markup?
Margin is profit as a percentage of the selling price; markup is profit as a percentage of the cost. A product bought for $80 and sold for $100 carries a 20% margin ($20 on $100) but a 25% markup ($20 on $80). The two are routinely confused, and the gap widens as the percentage grows.
Is R-value the same as insulation thickness?
No. R-value measures resistance to heat flow, not thickness. A thin sheet of rigid foam can carry a higher R-value than a thicker batt of fiberglass, because R-value depends on the material as well as the depth. Two inches of one material and two inches of another rarely share the same R-value.
Why does sample standard deviation divide by n minus one?
Dividing by n − 1 instead of n corrects a bias: a sample tends to underestimate the spread of the population it came from, because the sample mean sits closer to the sample's own points than the true mean does. The correction, called Bessel's correction, enlarges the estimate to compensate. Population standard deviation, where you have every data point, divides by n.
Does a lower cap rate mean a better property?
Not by itself. A cap rate is net operating income divided by price, so a lower cap rate means a higher price relative to income — which the market often assigns to properties seen as safer or in stronger locations. Whether that is 'better' depends on the risk you are pricing, not on the number alone.
Are these definitions financial or medical advice?
No. This glossary explains what each term means and how it is calculated, so the matching tool's output is legible. It is not advice. For a decision with money or health at stake, confirm with a professional who knows your situation.