Guides
In-depth guides on finance, text, and developer topics — with worked examples and free tools.
The guides on this site go deeper than the tools they're paired with — each one explains the concept behind a calculation or format, not just how to use the widget. A guide on tax brackets covers how marginal rates actually work; a guide on JSON covers why the format looks the way it does. They're written to stand on their own: useful whether or not you ever open the matching tool, and a place to check the reasoning behind a number before you rely on it.
Finance Guides
Browse Finance Guides tools →Mortgage amortization, compound interest, tax brackets, and retirement math explained with worked examples — the reasoning behind the numbers a calculator gives you, not just the formula.
What is Compound Interest?
How to Calculate ROI
How to Calculate a Tip
How to Create a Monthly Budget
What is a Mortgage?
How Tax Brackets Work
How to Calculate Net Worth
How to Calculate a Discount
How to Convert Hourly to Annual Salary
How to Pay Off Debt
How to Set a Savings Goal
What is Inflation?
How to Calculate a Percentage
What is APR?
How Interest Rates Work
What is Simple Interest?
How Loan Amortization Works
How Much Do You Need to Save for Retirement?
Developer Guides
Browse Developer Guides tools →What JSON, Base64, UUIDs, regex, and hashing actually are under the hood — written for the moment you need to explain a format to a teammate, not just run it through a tool.
What is JSON?
What is Base64?
Regex Tutorial
What is a JWT?
What is a Hash Function?
Markdown Guide
What is URL Encoding?
What is a Unix Timestamp?
What is a Cron Job?
Color Codes Explained
What is a User Agent?
Binary, Hex, and Decimal Explained
What is a UUID?
What is SQL?
What are HTML Entities?
How to Read a Diff
What is Minification?
What is HTTPS?
What is an API?
What is an HTML Beautifier?
Text Guides
Browse Text Guides tools →Word counts, reading time, character limits, and text formatting conventions explained for writers and editors who want the reasoning, not just a number.
How to Count Words
What is Lorem Ipsum?
What is a URL Slug?
How to Calculate Reading Time
Naming Conventions Explained
How to Find and Replace Text
How to Sort Lines of Text
How to Remove Duplicate Lines
How to Compare Two Texts
How to Remove Whitespace from Text
How to Count Lines in Text
How to Reverse Text
What is a Palindrome?
Image Guides
Browse Image Guides tools →Image formats, compression, and metadata explained — why WebP is usually smaller than PNG, what EXIF data actually contains, and other concepts behind the image tools.