Why these are grouped this way
Individually, most of the tools here answer one question. In practice, though, the situations people bring to a site like this rarely stop at one question. Someone working out a due date is going to want to know the baby's age in weeks a few months later. Someone running mortgage numbers is going to hit square feet versus square metres within about ten minutes. Someone generating a strong password is going to need a way to hand out their WiFi without reading twenty characters aloud.
So these guides follow the situation rather than the tool. Each one walks a real scenario end to end, uses two or three tools in the order you'd actually reach for them, and shows the numbers rather than describing them.
The guides
From cycle tracking to your baby's first birthday
The longest chain on the site, and the one most worth reading in order. Finding your fertile window, understanding why a due date is calculated from your last period rather than conception, reading gestational age the way a midwife reads it, and then switching to weeks-and-months once the baby arrives — because that's the unit every appointment for the next two years will use.
Uses the Period Calculator, Due Date Calculator and Age Calculator.
Buying a home: what the monthly payment isn't telling you
Why the first year of a mortgage is almost all interest, what an extra £100 a month actually buys you in years saved, how to compare a 25-year and a 30-year term honestly, and the property-listing unit conversions that trip people up constantly. Includes a worked amortisation example you can check line by line.
Uses the Mortgage Calculator, Unit Converter and Age Calculator.
Passwords, passphrases, and the five accounts that actually matter
What "entropy" means in numbers you can reason about, why a six-word passphrase beats a mangled dictionary word with a 3 for the E, which handful of accounts deserve unique credentials before all the others, and how to hand out your WiFi password without saying it out loud.
Uses the Password Generator and QR Code Generator.
Shipping a small website in an afternoon
A palette that passes contrast checks, placeholder text that doesn't lie to you about how the layout will hold up, a meta description that fits in the space Google gives it, an API response you can actually read, and a printable QR code at the end of it.
Uses the Color Picker, Lorem Ipsum Generator, Word Counter, JSON Formatter and QR Code Generator.
Getting better at Scrabble, Wordle and the rest
How to use an unscrambler to learn rather than just to win, the two-letter words that are worth more than any clever seven-letter play, why the same rack scores differently depending on where you put it, and how to practise in a way that transfers to games you play without a browser open.
Uses the Word Unscrambler and Word Counter.
A note on what these are
These are written by the person who built the tools, based on the questions that actually come in by email. They are not medical, legal or financial advice, and the health and money guides say so where it matters. Where a guide states a formula, that formula is written out in full on the methodology page so you can check it.