Math Guides & Tutorials
Short, practical explanations with worked examples. Each guide links to a free tool so you can try the idea on your own numbers.
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Calculator
How to Use a Scientific Calculator8 min read · Learn how to use a scientific calculator: order of operations, degrees vs radians, trig, l…
Calculator Code Mode: Expressions, Shortcuts and the 0000 Game Break6 min read · How Code Mode works: type whole expressions like sin(30)+2^3, use every supported function…
What Is a Calc Solver?6 min read · What a calc solver is, why people type it as calcsolver, calc solve or solve calc, what it…
How to Create a Strong Password5 min read · Learn what makes a password strong, how entropy and length work, how long cracking takes a…
How to Make a QR Code5 min read · Learn how to make a QR code for a link, Wi-Fi login or text, how error correction and size…
How Random Number Generators Work7 min read · Learn how computers make random numbers, pseudo-random versus cryptographic generators, an…
How to Improve Your Typing Speed6 min read · Learn how WPM is measured, what a good typing speed is and a 4-week practice plan with tou…
How to Use the Pomodoro Technique6 min read · Learn the Pomodoro Technique step by step: focus and break lengths, how many sessions fit …Arithmetic
Order of Operations: PEMDAS and BODMAS6 min read · Learn the order of operations: PEMDAS and BODMAS rules with worked examples, common traps …
How to Calculate Percentages7 min read · Learn how to calculate a percentage, percent change, discounts, tips and percentage increa…
How to Add and Subtract Fractions7 min read · Step-by-step guide to adding, subtracting, multiplying and dividing fractions, finding com…
How to Simplify Fractions5 min read · Learn to simplify fractions to lowest terms using the greatest common factor or repeated d…
How to Convert Units6 min read · Learn how to convert units of length, mass, volume, temperature and speed with conversion …
Ratios and Proportions Explained6 min read · Learn what ratios and proportions are, how to simplify ratios, solve missing values with c…
Converting Fractions, Decimals and Percents8 min read · Learn to convert between fractions, decimals and percents, including repeating decimals, w…
Equivalent Fractions6 min read · Understand equivalent fractions: how to make them, test them by cross-multiplying, and use…
Mixed Numbers7 min read · Learn mixed numbers and improper fractions: how to convert between them and how to add, su…
Negative Numbers7 min read · Understand negative numbers with the number line and learn the sign rules for adding, subt…
Place Value and Rounding7 min read · Learn place value from ones to billions and from tenths to thousandths, write numbers in e…
Multiplication Tricks7 min read · Fast multiplication tricks: times 9, 11, 5 and 25, squaring numbers ending in 5, double-an…
Scientific Notation7 min read · Learn scientific notation: writing large and small numbers, converting to and from standar…
Percentage Increase and Decrease7 min read · Learn to calculate percentage increase and decrease, reverse a percentage change, handle s…
How to Calculate a Tip and Split the Bill5 min read · Learn quick mental-maths ways to calculate 15%, 18% and 20% tips, how to split a bill fair…
How to Calculate Age in Years, Months and Days5 min read · Learn how to work out exact age from a birth date, including borrowing days, leap years, t…
How to Calculate a Discount5 min read · Learn how to calculate a percent-off discount, the sale price, stacked discounts and why t…
How to Calculate GPA (Semester, Cumulative and Weighted)7 min read · Learn how to calculate GPA on the 4.0 scale: semester GPA, cumulative GPA, weighted (honou…
How to Calculate Days Between Dates6 min read · Learn how to count the days between two dates by hand, handle months and leap years, count…
How to Calculate Fuel Cost for a Trip5 min read · Learn how to calculate fuel needed and trip cost from distance, fuel efficiency and price,…
How to Convert Cooking Measurements5 min read · Learn how to convert cups to grams, tablespoons to ml and ounces to grams for flour, sugar…
How to Convert Time Zones5 min read · Learn how to convert time between time zones, how UTC offsets and daylight saving work and…
How to Calculate a Weighted Grade7 min read · Learn how weighted grades work, how to calculate your current grade, the average you need …Algebra
Exponents and Powers Explained7 min read · Understand exponents and powers with the laws of exponents, negative and fractional expone…
How to Solve Quadratic Equations8 min read · Learn three ways to solve quadratic equations: factoring, completing the square and the qu…
Algebra Basics8 min read · Learn algebra from scratch: variables, expressions versus equations, simplifying, the dist…
Algebraic Expressions8 min read · Understand algebraic expressions: terms, like terms, simplifying, evaluating and expanding…
Polynomials Explained8 min read · Understand polynomials: terms, degree, standard form, monomials, binomials and trinomials,…
Factoring Polynomials9 min read · Learn how to factor polynomials: GCF, trinomials, the ac method, difference of squares, pe…
The Remainder and Factor Theorems7 min read · Understand the remainder theorem and factor theorem: how to find remainders without dividi…
Dividing Polynomials8 min read · Learn to divide polynomials with long division and synthetic division, handle remainders, …
Linear Equations9 min read · Learn linear equations: solving for x, slope-intercept form, finding an equation from two …
Basic Algebra Formulas7 min read · A clear algebra formulas cheat sheet: identities, exponent laws, the quadratic formula, sl…
Algebraic Fractions8 min read · Learn algebraic (rational) fractions: simplifying by factoring, multiplying, dividing, add…Numbers
Factors, Multiples, GCF and LCM7 min read · Understand factors, multiples, prime factorization, the greatest common factor (GCF) and l…
Binary, Decimal and Hexadecimal7 min read · Learn how number systems work: binary, octal, decimal and hexadecimal, place value, conver…
Prime and Composite Numbers7 min read · Learn what prime and composite numbers are, list the primes to 50, test any number by tria…
Divisibility Rules6 min read · Learn quick divisibility rules for 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11, why they work, and h…
Roman Numerals6 min read · Learn Roman numerals: the symbols I V X L C D M, the addition and subtraction rules, conve…Statistics
Geometry
The Pythagorean Theorem Explained6 min read · Understand the Pythagorean theorem a² + b² = c² with a visual proof, worked examples, Pyth…
Degrees vs Radians6 min read · Understand degrees and radians, how to convert between them, why calculators have DEG and …
Types of Triangles7 min read · Learn the types of triangles by sides and by angles, their properties, the triangle inequa…
Angles Explained8 min read · Learn angles: acute, right, obtuse and reflex, complementary and supplementary pairs, vert…
Area and Perimeter8 min read · Learn area and perimeter formulas for rectangles, triangles, parallelograms, trapezoids an…
Volume and Surface Area8 min read · Learn volume and surface area formulas for cubes, boxes, cylinders, cones and spheres with…
Coordinate Geometry7 min read · Learn coordinate geometry: plotting points, the four quadrants, the distance and midpoint …
Trigonometry Basics8 min read · Learn trigonometry basics: sine, cosine and tangent, SOH-CAH-TOA, finding angles and sides…Finance
How Compound Interest Works7 min read · Understand compound interest with the formula, worked examples, simple vs compound compari…
How Mortgage Payments Work7 min read · Understand how a fixed-rate mortgage payment is calculated, how amortization splits intere…
How to Calculate Your Mortgage Refinance Break-Even Point7 min read · Learn how to work out whether refinancing a mortgage pays off: monthly saving, closing-cos…
How to Pay Off Your Mortgage Early7 min read · Learn how extra monthly payments, lump sums and biweekly payments shorten a mortgage, how …
How to Calculate How Much House You Can Afford8 min read · Learn how to work out the home price you can afford with the 28/36 debt-to-income rule, wi…
How to Convert Hourly Wage to Annual Salary5 min read · Convert an hourly wage to an annual salary and back using the 2,080-hour year, plus weekly…
How Currency Exchange Rates Work6 min read · Learn how exchange rates are quoted, how to convert between currencies and cross rates by …
How to Calculate Retirement Savings8 min read · Learn how to project retirement savings with compound growth, adjust for inflation, apply …
How to Calculate Your FIRE Number7 min read · Learn how to calculate your FIRE number from spending and a withdrawal rate, how long it t…
How to Calculate a Car Loan Payment6 min read · Learn how to calculate a car loan payment from price, down payment, trade-in, sales tax, f…
How to Calculate Personal Loan APR6 min read · Learn how origination fees change a personal loan’s true cost, how APR differs from the in…
Rent vs Buy: How to Decide8 min read · Learn how to compare renting and buying a home using net worth, opportunity cost, upkeep a…
How to Calculate Inflation5 min read · Learn how to calculate inflation: the future cost of something, what money will be worth l…
How to Calculate Sales Tax, VAT and GST6 min read · Learn how to add tax to a price and remove it from a total for sales tax, VAT and GST, wit…
How to Write an Invoice6 min read · Learn what an invoice must include, how to calculate line totals, discounts, tax and the f…
How to Calculate EMI6 min read · Learn how to calculate a loan EMI with the formula, a worked example, how interest and pri…
How to Calculate SIP Returns6 min read · Learn how to calculate SIP maturity value with the formula, how a yearly step-up increases…
How to Calculate GST in India6 min read · Learn how to add GST to a price, remove it from a total and split it into CGST, SGST or IG…
New vs Old Tax Regime: Which Is Better?6 min read · Learn how to compare India’s new and old income-tax regimes for FY 2026-27, with slabs, de…
How to Calculate PPF Maturity6 min read · Learn how PPF interest is calculated, the 15-year rules, deposit limits and how to estimat…
How to Calculate FD and RD Maturity6 min read · Learn how to calculate fixed deposit and recurring deposit maturity with quarterly compoun…
How to Calculate CAGR and ROI6 min read · Learn how to calculate CAGR and ROI, the difference between them, annualised returns and c…
How to Calculate Work Hours and Overtime6 min read · Learn how to add up hours between start and end times, handle breaks and overnight shifts,…
Debt Snowball vs Debt Avalanche7 min read · Learn how the debt snowball and debt avalanche methods work, with a worked comparison of t…
How eBay Fees Work7 min read · Learn how eBay charges US sellers: final value fees by category, the per-order fee, fees o…Health
How to Calculate BMI6 min read · Learn how to calculate body mass index with the metric and imperial formulas, worked examp…
How to Calculate TDEE and Daily Calories7 min read · Learn how to calculate BMR, TDEE and daily calorie targets step by step with the Mifflin–S…
How to Calculate Body Fat Percentage6 min read · Learn how to measure and calculate body fat percentage using the US Navy tape-measure meth…
How to Calculate Your Pregnancy Due Date7 min read · Learn how due dates are calculated with Naegele’s rule, how to work out ovulation and the …
How to Calculate Sleep Debt6 min read · Learn how to calculate sleep debt from your nightly hours, what the CDC recommends by age …
How Much Caffeine Is Too Much?6 min read · Learn the FDA’s 400 mg guidance, how much caffeine is in coffee, tea, soda and energy drin…
How to Calculate Your One-Rep Max7 min read · Learn how to estimate your one-rep max from a lighter set, the main formulas, how accurate…