Tutorials, deep dives, and how-tos.
Practical guides on image formats, PDF tricks, security, and developer tools. No fluff, no signup, no paywall.
How to calculate the number of days between two dates
Counting days by hand is error prone because months differ and leap years exist. Here is the reliable method, inclusive vs exclusive counting, and business days.
Latest articles
16:9 in pixels: the complete resolution reference
16:9 is a shape, and dozens of pixel resolutions share it, from 1280x720 up to 8K. Here is what 16:9 means in pixels, with a full resolution table.
How many hours is a 9 to 5? Common shifts explained
A 9 to 5 is 8 hours gross, or 7.5 hours after a 30 minute lunch. Here are the real worked hours for common shifts, with a table and how to count them.
Cubic yards to tons of gravel: the conversion explained
Suppliers sell gravel by the ton or the cubic yard. One cubic yard is about 1.4 tons. Here is how to convert both ways, with a table and coverage figures.
How to stack discounts: why 30% off then 20% off is not 50%
Stacked discounts multiply, they do not add. Here is how to work out the real total percent off when a coupon stacks on a sale, with a quick reference table.
Weighted vs unweighted GPA and the 5.0 scale explained
The difference between the 4.0 unweighted scale and the 5.0 weighted scale, how honors and AP classes add points, and how to calculate a weighted GPA, with a grade table.
How to read scientific notation (what 1.5e12 means)
What the e in a number like 1.5e12 means, how to read positive and negative exponents, and how to convert scientific notation to a plain number and back, with a reference table.
Reverse sales tax: how to find the price before tax
How to work backward from a total that already includes tax to find the pre-tax price and the tax portion, why you cannot just subtract the percentage, and a quick reference table.
How many tons of gravel do I need? (cubic yards to tons)
How to calculate gravel for a driveway or patio, convert cubic yards to tons, and the density numbers that make the math right. With a coverage lookup table.
How to calculate flooring square footage (formula, waste, examples)
The exact way to measure a room and calculate how much flooring to buy, including the waste factor pros use so you never run short. With a room-size lookup table.
Aspect ratio explained: how to calculate 16:9, 4:3, and 21:9
What aspect ratio means, how to calculate it for any width and height, and the exact pixel dimensions for 16:9, 4:3, 21:9, and 1:1. With a full resolution lookup table.
How to remove EXIF and location data from your photos
What EXIF metadata reveals about you, including GPS location, and how to strip it from any photo in your browser before you share it.
How to calculate a discount and the percentage off
The discount formula, quick mental math tricks for 10, 20, 25 and 50 percent off, how stacked discounts really work, and how to find the original price.
How to calculate hours worked between two times
The simple way to add up hours from a start and end time, subtract a lunch break, handle overnight shifts, and convert minutes to decimal hours for payroll.
Mortgage payments explained: how the monthly math actually works
The amortization formula in plain English. Why your first payment is almost all interest, how a 30-year vs 15-year mortgage really compares, and what changes when rates move 1%.
Feet to meters: a complete conversion guide (with tables)
The exact conversion, the mental-math shortcut, and a lookup table for the most-searched values. Plus when 1 foot does not equal 0.305 meters.
How to calculate BMI: formula, examples, and healthy ranges
Body Mass Index in plain English. The formula in both metric and imperial, worked examples, and what the categories really mean.
How much paint do I need? A room-by-room guide with examples
The formula, the coverage cheat sheet, and the room-size lookup table. Learn how to calculate gallons of paint for any room without buying too much or running short.
How to merge PDFs without uploading them (2026 privacy guide)
Most online PDF mergers send your files to a remote server. Learn the techniques and tools that merge PDFs entirely in your browser, so signed contracts and tax returns never leave your device.
Markdown explained: a complete guide for writers and developers
Markdown is the writing format that powers GitHub, blog platforms, Notion, and countless other tools. Learn the syntax, the GitHub Flavored extensions, common pitfalls, and when to use HTML instead.
JWT explained: how JSON Web Tokens really work (with examples)
Demystify JSON Web Tokens. Learn what each part of a JWT means, how signing works, when to use them, and the security pitfalls that have leaked production tokens.
HEX, RGB, HSL, CMYK: every color format explained
Designers and developers work with colors in different formats. Learn what each one means, when to use it, and how to convert between them.
MD5 vs SHA-256: which hash should you use today?
Hashing is everywhere from passwords to file integrity to blockchains. Here is when to use MD5, SHA-1, SHA-256, and why the answer is almost always SHA-256.
UUID v4 explained: a developer's guide to unique identifiers
What UUIDs are, why version 4 became the default, and when to use them instead of auto-increment database IDs.
What is Base64 encoding? (with real-world examples)
Base64 turns any binary data into safe ASCII text. Learn how it works, when to use it, and why it is not encryption.
PNG vs JPG vs WebP: which image format should you use?
A practical breakdown of the three most common web image formats. When to use each, how they compress, and how to pick the right one for your project.