Guides, tips, and how-tos for getting the most out of our free online tools.
Most percentage problems are one of three types. Learn the formula for each — and when to use it — with worked examples.
2026-06-03 · 5 min read
Subtracting years is not the same as your real age. Here is how exact age is actually calculated — and the leap-year trap to avoid.
2026-06-03 · 4 min read
BMI is the world's most common weight screening number. Here is the formula, the categories, and what BMI does — and does not — tell you.
2026-06-03 · 5 min read
Your monthly loan payment is more than the amount divided by the term. Here is how EMI works and how to spot the true cost of a loan.
2026-06-03 · 6 min read
A "30% off" sign tells you the discount, not what you pay. Here is how to find the real final price — including tax.
2026-06-03 · 4 min read
A handful of conversion factors cover most daily needs. Here they are — plus the one conversion you cannot do with a simple multiply.
2026-06-03 · 5 min read
Hashes power downloads verification, password storage, and blockchains. Here is what they are, in plain terms.
2026-06-03 · 5 min read
That big number in your logs is Unix time. Here is how it works, why it has no timezone, and the famous 2038 bug.
2026-06-03 · 5 min read
HEX, RGB, and HSL describe the same colors in different ways. Here is when each one shines.
2026-06-03 · 4 min read
Sending loose photos looks messy. Here is how to merge images into one clean PDF — without handing your files to a server.
2026-06-03 · 4 min read
Picking the wrong URL-encoding function silently breaks query strings. Here is exactly when to use each one.
2026-06-03 · 5 min read
Splitting a CSV on commas works until a value contains a comma. Here is how real CSV parsing handles the messy cases.
2026-06-03 · 5 min read
Why is memory measured in hex and permissions in octal? A practical tour of the number systems programmers actually use.
2026-06-03 · 6 min read
Square for avatars, 16:9 for thumbnails. Here is how aspect ratios work and how to crop to them cleanly.
2026-06-03 · 4 min read
Pasted text full of broken line breaks and double spaces? Here is why it happens and how to fix it in one click.
2026-06-03 · 4 min read
A clean slug helps users and search engines understand a page before they open it. Here are the rules worth following.
2026-06-03 · 4 min read
A long passphrase beats a short jumble of symbols. Here is the maths behind password strength — and how to get it right.
2026-06-03 · 5 min read
From contactless menus to guest Wi-Fi, QR codes bridge print and digital. Here is how to use them well.
2026-06-03 · 5 min read
Trailing commas, single quotes, missing brackets — the usual suspects behind "Unexpected token". Here is how to fix them fast.
2026-06-03 · 5 min read
A JWT is not encrypted — anyone can read it. Here is what the three parts contain and why that matters for security.
2026-06-03 · 5 min read
Most email services cap attachments around 25 MB. Here is how to get a bloated PDF under the limit.
2026-06-03 · 4 min read
Marketplaces demand clean backgrounds. Here is how automatic background removal works and how to get crisp cutouts.
2026-06-03 · 4 min read