Guides & explainers
In-depth guides explaining how the calculations work and how to use the tools — grouped by topic.
Calculators 44Converters 11Developer & App Tools 5Generators & Encoders 2Text & Writing 5Date & Time 2
Calculators
Algebra & Functions: Linear, Quadratic & Exponential
Understand linear, quadratic, and exponential functions — their equations, graphs, slopes,
Automotive & Engineering Calculations: A How-To Guide
Understand horsepower, torque, gear ratios, engine displacement, tire sizing, and EV metri
BMI & Body Weight Calculators: What They Measure and How to Use Them
Learn how BMI, body fat percentage, ideal weight, and waist ratios are calculated -- with
Business & Finance Calculators: Metrics, Formulas, and How to Use Them
Learn profit margin, CAC, LTV, MRR, ROAS, and more -- with exact formulas, a worked SaaS e
Business & SaaS Metrics: A Complete Guide to the Numbers That Drive Growth
Learn how to calculate LTV:CAC, churn rate, burn rate, gross margin, and more. Free calcul
Calorie & Nutrition Calculators: How to Use Them and Why They Work
Learn how BMR, TDEE, macro, and calorie calculators work -- with formulas, examples, and t
Clinical Health Metrics Explained: MAP, QTc, LDL, Creatinine Clearance, and Body Composition
Understand MAP, QTc interval, LDL (Friedewald), creatinine clearance, corrected calcium, a
Credit Card & Debt Payoff: A Complete Strategy Guide
Learn how minimum payments, interest, APR, and payoff strategies work. Compare snowball vs
Crypto Investing & Position Sizing: A Practical Guide
Learn how to size crypto positions, calculate leverage and liquidation prices, track DCA c
Date & Time Calculators: How to Calculate Days, Deadlines, and Date Differences
Learn how to count days between dates, add days to a date, find a day of the week, and cal
Debt & Credit Calculators: How to Understand and Eliminate Debt
Learn how credit card payoff, debt snowball, DTI ratio, and other debt calculators work —
Descriptive Statistics: Mean, Median, Mode, Standard Deviation, and More
Learn how mean, median, mode, standard deviation, variance, and z-scores describe data — w
Electronics Fundamentals: Ohm's Law, RC Circuits, Voltage Dividers, and More
Master Ohm's Law, RC time constants, voltage dividers, LC resonance, and LED resistor sizi
Everyday Life Calculators: Your Guide to Smarter Daily Decisions
Discover how everyday life calculators for fuel, tips, GPA, electricity, and more can help
Fractions, Ratios, and Proportions: Formulas, Examples, and How to Simplify
Master fractions, ratios, and proportions with clear formulas, worked examples, and tips f
Freelancer & Contractor Pay: How to Price Your Work
Understand how to set a freelance hourly rate, build a project quote, calculate take-home
Geometry Calculators: Area, Volume, Perimeter, and Distance Explained
Understand the geometry formulas behind area, volume, perimeter, and distance calculations
Health & Lifestyle Medical Metrics: A Practical Guide
Understand blood glucose, A1C, kidney function (eGFR), blood pressure, anion gap, sleep de
Health Insurance Benefits Explained: HSA, FSA, COBRA, Coinsurance, and More
Learn how HSAs, FSAs, COBRA, coinsurance, out-of-pocket maximums, and ACA subsidies work —
Heart Rate Training Zones & Fitness Metrics: A Full Guide
Learn how to calculate max heart rate, training zones, VO2 max, rep maxes, hydration needs
Home & Construction Material Estimating: A Complete Guide
Learn how to accurately estimate drywall, lumber, roofing, concrete, gravel, mulch, bricks
Home Buying & Selling Costs: What to Expect at Closing
From down payments and closing costs to PMI, earnest money, and seller net proceeds, learn
Home Construction & Renovation: A Complete Cost Estimating Guide
Estimate paint, roofing, insulation, fencing, stairs, trim, countertops, and siding costs
Home Energy & Utilities Savings: A Complete Guide
Learn how to cut electricity bills, size solar panels, evaluate heat pumps, and eliminate
Income and Payroll Taxes Explained: Marginal Rates, Effective Rates, FICA, Capital Gains, and More
Understand how marginal and effective tax rates differ, how FICA and self-employment taxes
Interest & Savings Calculators: Formulas, Examples, and How to Use Them
Understand compound interest, savings goals, APY, and more -- with clear formulas, a worke
Mortgage & Loan Calculators: The Complete Guide to Planning Your Debt
Understand how mortgage and loan payments are calculated, read an amortization schedule, a
Mortgage & Loan Payment Types: A Complete Guide
Explore biweekly payments, mortgage points, HELOC, interest-only loans, balloon mortgages,
Mortgage Affordability, Amortization, Refinancing, and DTI: The Complete Guide
Learn how much mortgage you can afford, how amortization works, when refinancing makes sen
Number & Arithmetic Calculators: GCD, LCM, Factorials, Logarithms & More
Explore the maths behind GCD, LCM, prime numbers, factorials, roots, powers, logarithms, m
Percentage Calculations: Formulas, Examples & Tips
Master every type of percentage calculation — find a percent of a number, calculate change
Personal Budgeting and Savings: How to Build a Plan That Works
Learn the 50/30/20 rule, sinking funds, savings timelines, and paycheck budgeting with cle
Physics Formulas & Calculations: A Practical Reference Guide
Master kinetic energy, potential energy, force, work, power, projectile motion, wave equat
Pregnancy Due Date, Weeks, and Ovulation: What the Numbers Mean
Understand how due dates are calculated, how to count pregnancy weeks, and when your ferti
Rental Property Metrics Every Investor Should Know
Master NOI, DSCR, cash flow, OER, equity multiple, debt yield, and fix-and-flip ROI to eva
Retirement & Investing Calculators: Formulas, Examples, and Strategy
Master ROI, CAGR, 401(k) growth, Roth IRA, FIRE, and more -- with clear formulas, a real e
Retirement Planning: FIRE, RMDs, Roth vs Traditional, Social Security, and Annuities
Learn how to use Coast FIRE, RMDs, Roth vs Traditional comparisons, Social Security estima
Salary and Income Conversions Explained: From Hourly to Annual Pay
Learn how to convert salary to hourly rate, annualize wages, project lifetime earnings, an
Sales Tax and Capital Gains Tax Explained: Calculators and Key Concepts
Learn how sales tax, capital gains tax, and income tax work worldwide, with worked example
Sports & Fitness Performance Calculators: A Complete Guide
Learn how to use running pace, cycling power, Wilks score, and other sports performance ca
Stock & Investment Returns: Key Metrics Explained
Understand dividend yield, bond YTM, expense ratios, DCA, Sharpe ratio, and capital gains
Stoichiometry and Solution Chemistry: Moles, Molarity, pH, and Yield
Learn how to convert between moles, grams, and particles; calculate molarity, pH, and perc
Student Finance & Academic Success: A Complete Guide for Students and Parents
From GPA calculation and exam planning to 529 savings and student loan payoff, learn the k
The True Cost of Owning a Car: Beyond the Sticker Price
Discover every cost involved in buying and owning a car—depreciation, fuel, insurance, and
Converters
Area Unit Conversion: Square Feet, Meters, Acres & More
Understand area units — square feet, square meters, acres, hectares — with conversion form
Cooking Measurement Conversions: Cups, Grams, Oven Temperatures, and Cook Times
Convert cups to grams, oven temperatures between Celsius and Fahrenheit, scale recipes, an
Data Storage Units Explained: From Bytes to Terabytes
Understand bytes, kilobytes, megabytes, gigabytes, and terabytes with clear formulas, real
Energy and Power Unit Conversion: Horsepower, Kilowatts, and Beyond
Learn how to convert between horsepower, kilowatts, joules, BTUs, and other power and ener
Length & Distance Unit Conversion: Every Formula You Need
Master length and distance conversions between metric and imperial units. See the exact fo
Number Base & Color Code Converters: Binary, Hex, and Beyond
Learn how binary, decimal, and hexadecimal number systems work, and how color codes like R
Screen Resolution, PPI, and TV Size: A Complete Guide
Understand pixels per inch, digital resolution, optimal TV viewing distance, and how to ch
Speed Unit Conversion: MPH, KM/H, Knots & More
Convert speeds between MPH, KM/H, knots, and m/s with clear formulas, worked examples, and
Temperature Conversion: Celsius, Fahrenheit & Kelvin
Learn the formulas for converting between Celsius, Fahrenheit, and Kelvin, with worked exa
Volume and Liquid Unit Conversion: Everything You Need to Know
Learn how to convert liters, gallons, milliliters, fluid ounces, cups, and pints with form
Weight & Mass Unit Conversion: Kilograms, Pounds, Stone, Ounces & More
Master weight and mass conversions between metric and imperial units. Includes exact formu
Developer & App Tools
Data Format Converters: Convert, Filter, Sort, and Compare Structured Data
Learn how to convert between CSV, JSON, YAML, and XML formats, filter and sort data, remov
Developer Utility Tools: Format, Encode, Test, and Hash in the Browser
A practical guide to browser-based developer utilities — JSON formatting, regex testing, e
Image Editing & Conversion: A Complete How-To Guide
Learn how to resize, compress, crop, convert, and transform images for web and print with
Online Audio & Media Tools: Tone Generator, Metronome, White Noise & More
Learn how online audio tools — tone generators, metronomes, binaural beats, white noise ge
PDF and Document Tools: Create, Merge, Split, and Extract Without Software
Learn how to create PDFs from text and Markdown, merge or split files, rotate pages, and e
Generators & Encoders
Text & Writing
Text Analysis & SEO Writing Tools: A Practical Guide
Learn how to use reading level scores, headline analysis, UTM tracking, passive voice dete
Text Analysis and Word Count Tools: What They Measure and Why It Matters
Understand word counts, character limits, reading time, keyword density, and SEO text metr
Text Case Converters: Uppercase, Lowercase, Title Case, CamelCase & More
Learn when and how to use uppercase, lowercase, title case, camelCase, snake_case, and keb
Text Cleaning Tools: Remove Clutter from Any Text
Learn when and how to clean text — removing duplicate lines, extra spaces, line breaks, em
Text Formatting & Transformation Tools: A Practical Guide
From URL slugs and sorted lines to reversed text and find-and-replace, learn when and how