Guides & how-tos
Plain-English explanations of the concepts behind our tools — how mortgages, percentages, compound interest, image formats and more actually work, with worked examples you can follow.
How to Calculate a Mortgage Payment (With Real Examples)
The number your lender quotes isn't magic — it comes from one formula. Here's how a monthly mortgage payment is built, with examples you can follow.
Image ToolsPNG vs JPG vs WebP: Which Image Format Should You Use?
Three formats, three jobs. Here's how PNG, JPG, and WebP compress images differently — and how to pick the right one every time.
Developer ToolsHow to Create a Strong Password (and Why Length Beats Complexity)
Symbols and capital letters help less than you think. The single biggest factor in password strength is length — here's why, with the math.
Finance ToolsHow Compound Interest Works (and Why Time Is Everything)
Compound interest is often called the eighth wonder of the world. Here's the mechanism behind it — and why starting early matters more than starting big.
CalculatorsHow to Calculate Percentages Fast (Every Formula Explained)
Percent just means 'per hundred'. Once that clicks, every percentage question — discounts, tips, tax, growth — reduces to one of a few simple formulas.
CalculatorsBMI Explained: What the Number Means and Where It Falls Short
BMI is a quick population-level screening number, not a verdict on your health. Here's what it measures, and the several things it can't see.
Developer ToolsBase64 Encoding Explained for Developers
Base64 turns binary data into plain text so it can travel through text-only channels. Here's how the encoding works and where you'll actually meet it.