Toolwell Blog

Calculating a percentage is one of the most useful everyday math skills. Learn the single formula behind every percentage problem, with worked examples you can use today.

Body Mass Index (BMI) is a quick screening tool based on height and weight. Learn the BMI formula, how to calculate it at home, and what the categories actually mean.

CSS minification strips away whitespace, comments, and unneeded characters. Learn how it shrinks file sizes, why smaller stylesheets load faster, and when to minify.

Markdown is everywhere — READMEs, docs, comments, and notes. Learn how to convert Markdown to HTML, why the conversion matters, and the tools that do it instantly.

Aspect ratio is the proportional relationship between an image’s width and height. Learn what 16:9 and 4:3 mean and how to calculate missing dimensions without cropping surprises.

Compound interest is how savings grow and how debt balloons. Learn the compound interest formula, see it in action with worked examples, and understand why time beats rate every time.

Never fumble the math at the table again. Learn how to calculate a tip by percentage, how to split a bill evenly or by what each person ordered, and the tricks servers use.

Regex looks like gibberish until you learn its building blocks. Understand patterns, character classes, and quantifiers with real examples you can test in seconds.

Title case, sentence case, camelCase, snake_case, kebab-case — learn what each text case is, when to use it, and how to convert between them without retyping a single word.

Deadlines, deliveries, and billing cycles all come down to one number: the days between two dates. Learn how to count them accurately, including leap years and holidays.

A practical, developer-friendly breakdown of when to use rem and when to use px in CSS — and why the choice affects accessibility, maintainability, and the quality of your design system.

Word count targets are everywhere — essays, blog posts, ad copy, and more. Here is how to use a word and character counter to meet limits, tighten your drafts, and write with more control.

Base64 lets you represent binary data as plain text. Learn how it works, why it is used for email attachments, data URLs, and APIs, and where it is (and is not) secure.

Length beats complexity. Learn what actually makes a password strong, how password generators create secure strings, and how to store them so you never reuse a weak one again.

JSON is the language of APIs and config files. Learn what valid JSON looks like, how to format it for readability, and how to catch the tiny errors that break your requests.

HEX and RGB are the two most common ways to write colors in CSS. Learn how to convert between them, when to use each, and why modern CSS is pushing developers toward yet another format.

Percentages appear in discounts, salary changes, growth reports, and grades. Learn the one formula behind them all, how to avoid the most common error, and how to check your math in seconds.

UUIDs give every row, file, and event a globally unique identifier without a central authority. Learn how UUID v4 works, when to reach for it, and when sequential IDs are still the better choice.

Recipes, weather reports, science experiments, and travel all use different temperature scales. Learn the formulas for converting Celsius, Fahrenheit, and Kelvin — and the mental shortcuts that cover most real-life cases.

QR codes went from convenience to everyday necessity. Learn how they work, how to generate one for any text or URL, and — most importantly — how to scan them without falling for a phishing link.