Blog & Guides
In-depth explainers on developer tools, calculators, and online utilities. Learn the math and code behind 367 free tools.
20 articles
What Is Base64 Encoding? A Complete Guide
Learn how Base64 encoding works, why it exists, and when you should (and shouldn't) use it โ with a step-by-step example.
How to Calculate BMI: Formula, Ranges, and Limitations
The complete guide to Body Mass Index โ the formula, WHO ranges, what BMI actually tells you, and its well-known limitations.
How Mortgage Payments Are Calculated: The Math Behind Your Monthly Bill
Understand the amortization formula, how your payment splits between principal and interest, and how extra payments can save you thousands.
What Is JSON? A Complete Beginner's Guide
JSON explained from the ground up โ syntax rules, data types, nested structures, comparison with XML, and common pitfalls to avoid.
Compound Interest Explained: The Most Powerful Force in Finance
How compound interest works, the formula, compounding frequencies, the Rule of 72, and why it matters for both savings and debt.
CSS Color Formats Explained: Hex, RGB, HSL โ Which Should You Use?
A complete comparison of CSS color formats โ how hex, RGB, HSL, and modern color functions work, and when to use each one.
How to Generate Secure Passwords: What Makes a Password Unbreakable
Learn what makes passwords truly secure โ entropy, length vs complexity, attack types, and how to generate passwords that can't be cracked.
What Is a Unix Timestamp? Everything Developers Need to Know
Unix timestamps explained โ the epoch, UTC vs local time, milliseconds vs seconds, the Year 2038 problem, and working with timestamps in code.
JWT Tokens Explained: How JSON Web Tokens Work
A complete guide to JSON Web Tokens โ the three-part structure, signing algorithms, security considerations, and when to use JWTs vs sessions.
Percentage Calculations: The Complete Guide with Formulas
Master every type of percentage calculation โ basic percentages, percentage change, working backwards, and real-world examples for discounts, tax, and grades.
Binary, Octal, Decimal, Hex: Number Systems Explained
Understand how binary, octal, decimal, and hexadecimal number systems work, why computers use them, and how to convert between bases.
How Currency Exchange Rates Work: A Plain-English Guide
Understand spot rates, bid/ask spreads, what moves exchange rates, and how to get the best rate when converting currency for travel or business.
Understanding TDEE and Macros: How to Calculate Your Daily Calorie Needs
A complete guide to calculating your TDEE (Total Daily Energy Expenditure) and macros โ the Mifflin-St Jeor formula, activity multipliers, and practical nutrition planning.
How EMI Is Calculated: Understanding Your Loan Repayment
A complete guide to EMI calculation โ the formula, flat rate vs reducing balance, how tenure affects total interest, and prepayment benefits.
Regular Expressions (Regex) for Beginners: A Practical Guide
Learn regex from scratch โ syntax, character classes, quantifiers, anchors, and 10 practical patterns for validating emails, URLs, phone numbers, and more.
How to Calculate ROI: Formulas, Examples, and Common Mistakes
Master ROI calculation โ the basic formula, annualized ROI, what counts as costs and gains, and how ROI compares to IRR and NPV.
Markdown Syntax Guide: A Complete Reference
The complete Markdown syntax reference โ headings, bold, italic, code, tables, links, images, lists, and GitHub Flavored Markdown extensions.
YAML vs JSON: When to Use Each and Key Differences
A complete comparison of YAML and JSON โ syntax differences, YAML gotchas (the Norway problem!), and when each format is the right choice.
Password Entropy: Why Longer Is Always Better
Understand password entropy in bits, how crack time scales with length, NIST 2024 guidelines, and why a 5-word passphrase beats a complex 8-character password.
CSS Specificity Explained: Why Your Styles Aren't Applying
Master CSS specificity โ how the cascade works, the specificity scoring system, the !important rule, and practical strategies to avoid specificity wars.