Guides
Short, practical explanations of the topics behind our tools.
How to Compress Images for the Web
Pick the right format, quality and size to keep images small and sharp.
How to Count Words and Estimate Reading Time
What counts as a word, and how reading time is calculated.
How to Format and Validate JSON
The strict rules of JSON, common errors and how to fix them.
What Is Base64 and When Should You Use It?
How Base64 encoding works, where it appears and its size trade-off.
Text Case Styles Explained
Title Case, Sentence case, camelCase, snake_case and when to use each.
How to Create a Strong Password
Why length matters, why uniqueness matters and how to generate one safely.
Understanding BMI and Its Limits
How Body Mass Index is calculated, its categories and what it cannot show.
How to Convert PSD Files to PNG or JPG
Choosing between PNG and JPG, and why some PSD files will not convert.
Metric and Imperial Conversions Explained
Exact factors for length, weight and temperature, with examples.
HEX, RGB and HSL Color Codes Explained
What each colour format means and when to use it.
How to Count Days Between Two Dates
Subtraction, leap years and counting rules that avoid mistakes.
How to Calculate Percentages
The three common percentage cases, with worked examples.
How QR Codes Work and How to Make a Good One
Error correction levels, print size and how to test a code.
How to Verify a Download with a Hash
Check a file against a SHA-256 checksum, and why SHA-1 is not enough.
How a Loan EMI Is Calculated
The EMI formula, why early payments are mostly interest, and how the term matters.
What Is Lorem Ipsum?
Where placeholder text comes from and how to use it in layouts.
How to Time Tasks with a Stopwatch
Lap timing, practice tracking and the Pomodoro method.
How to Resize an Image to a Specific File Size
Meet a file size limit in KB, such as 20 KB for a form.
How to Convert JPG to WebP (and Back)
When WebP helps, when to keep JPG or PNG, and how to convert.
Is It Safe to Merge PDF Files Online?
What online PDF tools do with your files, and how to check.
How to Convert Video to MP3 (Safely and Legally)
Extract audio from a video you own, and the copyright points to check.
How to Calculate Your Exact Age in Years, Months and Days
The borrowing rule, a worked example, and days to your next birthday.
Lossy vs Lossless Compression: What Changes in Your Images
What compression removes, which formats use each, and quality settings.
How to Compare Two Texts for Differences
How to spot what changed between two versions of a document, contract or code file, line b
How to Calculate a Discount and Sale Price
How to work out a sale price from a percentage discount, how much you save, and how sales
What Is URL Encoding (Percent-Encoding)?
What URL encoding does, why spaces become %20, which characters need encoding, and when to
How Compound Interest Works, With a Worked Example
How compound interest grows savings, how the number of compounding periods changes the res
How to Split a Bill Fairly, Including the Tip
How to work out the tip, the total and each person's share of a restaurant or group bill,
How a SIP (Monthly Investment Plan) Works
What a systematic investment plan is, how monthly payments grow with compounding, and what
How GST Is Calculated: Adding and Removing Tax
How goods and services tax is calculated when it is added to a price, and how to work back
What Is a Unix Timestamp? Epoch Time Explained
What Unix epoch time is, how seconds since 1 January 1970 represent a date, and the common
How Roman Numerals Work
The seven Roman numeral letters, the subtraction rule for numbers like IV and XC, and how
What Is a Regular Expression? A Beginner Guide
What a regular expression (regex) is, the building blocks such as character classes, quant
How to Measure Your Typing Speed and Accuracy
How words per minute is calculated, why accuracy matters as much as speed, and how to get
CSV vs JSON: Which Format Should You Use?
The differences between CSV and JSON, when each one is the better choice, and the common m
What Is Markdown? A Simple Guide to Writing for the Web
What Markdown is, the basic syntax for headings, bold text, links and lists, and where it
How to Check Password Strength (and What the Scores Miss)
How password strength is estimated from length and character variety, why common words and