Everyday Math

Practical formulae for daily life: shopping, cooking, travel, and home projects.

Everyday Math brings together the practical formulas you use in real life, from comparing shopping deals and calculating tips to planning travel, scaling recipes, and estimating materials for home projects. It’s a helpful reference for students, exam prep, and anyone doing everyday work where quick, accurate calculations save time, money, and hassle.

Unit Price

\text{Unit Price} = \frac{\text{Total Price}}{\text{Quantity}}

Price per single unit to compare value between products.

Discount Price

\text{Final} = P(1 - d)

Price after a percentage discount.

Sales Tax Total

\text{Total} = P(1 + t)

Final price including sales tax.

Tip Amount

\text{Tip} = B \times r

Gratuity based on a bill amount.

Fuel Economy (mpg)

\text{mpg} = \frac{\text{Miles}}{\text{Gallons}}

Distance traveled per gallon of fuel.

Trip Fuel Cost

\text{Cost} = \frac{D}{E} \times p

Total fuel cost for a trip.

Average Speed

v = \frac{d}{t}

Distance covered per unit time.

Travel Time

t = \frac{d}{v}

Time needed to cover a distance at a given speed.

Recipe Scaling

Q_{new} = Q_{old} \times \frac{S_{new}}{S_{old}}

Adjust ingredient quantities for a different number of servings.

Paint Needed

\text{Gallons} = \frac{A}{C}

Amount of paint required for a wall area.

Tiles Needed

N = \frac{A_{floor}}{A_{tile}}

Number of tiles to cover a floor.

Room Area

A = l \times w

Floor area of a rectangular room.

Simple Interest

I = P r t

Interest earned or owed without compounding.

Celsius to Fahrenheit

F = \frac{9}{5}C + 32

Convert temperature from Celsius to Fahrenheit.

Body Mass Index

BMI = \frac{m}{h^2}

Weight-to-height ratio used as a health screening tool.

Percentage Change

\%\Delta = \frac{new - old}{old}\times 100

Relative change between two values.

Split the Bill

\text{Each} = \frac{T(1+r)}{n}

Per-person share of a bill including tip.

Monthly Loan Payment

M = P\frac{r(1+r)^n}{(1+r)^n - 1}

Fixed monthly payment for an amortizing loan.

Weight Loss Estimate

\Delta w = \frac{\text{deficit} \times days}{7700}

Approximate body-mass loss from a calorie deficit (kg).

Aspect Ratio Scaling

h = w \times \frac{r_h}{r_w}

Find a height that preserves an aspect ratio.