These posts go a level deeper than the tool pages themselves — the reasoning behind a format choice, the edge cases that trip people up, and the small decisions (PNG vs. JPEG, AA vs. AAA contrast, when a semicolon breaks your JSON) that a one-line tool description doesn't have room for. New posts get added as tools are added or as recurring questions come up in tool feedback.
All guides
How to Calculate Your Final Grade
Grade percentages, weighted categories, points-based classes, and the formula for the score you need on the final, with worked examples.
CONVERTER TOOLSHow to Convert Binary to Decimal and Decimal to Binary
Two step-by-step methods in each direction, a 0–15 binary table, and the hexadecimal shortcut for long numbers.
CONVERTER TOOLSEST vs EDT and PST vs PDT: Which Applies Right Now?
Standard vs daylight time on both coasts, the federal rule, exact 2026–2027 change dates, and a live check of which applies now.
CONVERTER TOOLSUTC vs GMT: What's the Difference?
Atomic time vs solar time, leap seconds, why London isn't on GMT in summer, and what the Z in a timestamp means.
TEXT TOOLSHow Many Words Is a Page? Words Per Page by Font and Spacing
Words per page by font, size and spacing with the assumptions shown, plus how long 1,000 words takes to read.
CONVERTER TOOLSHow to Calculate Percentage: Formulas and Examples
The three core percentage formulas, percent change, and reverse percentages like finding an original price, each with worked examples.
DEVELOPER TOOLSchmod 777, 755 and 644 Explained: Linux File Permissions
How each chmod digit adds up from read, write and execute, why 777 is risky, and when to use 755, 644 or 600 instead.
DEVELOPER TOOLSJSON vs XML: Key Differences and When to Use Each
The same data in both formats, data types, comments, JSON Schema vs XSD, measured file sizes, and what breaks when you convert.
DEVELOPER TOOLSCSS Grid vs Flexbox: When to Use Each (With Examples)
One-dimensional vs two-dimensional layout, a decision checklist, copy-ready CSS for common patterns, and how to combine both.
GUIDEHow to Find the BPM of a Song: Tap, Count or Calculate
Tap tempo, the 15-second count, half-time and double-time mix-ups, and a chart of delay times in milliseconds for common tempos.
CONVERTER TOOLSWhy Your Unit Conversion Doesn't Match: Rounding Errors Explained
Two converters, two slightly different answers for the same conversion — why that happens, and when the difference actually matters.
GENERATOR TOOLSAre Online Password Generators Safe? How Client-Side Generation Works
What actually makes a browser-based password generator trustworthy — and how to check any tool yourself in under a minute.
TEXT TOOLSWord Count vs. Character Count: Which One Actually Matters?
Essays, tweets, and meta descriptions all measure "length" differently. Here's how each one is actually calculated.
HOROSCOPE TOOLSHow Do Compatibility Calculators Actually Work? Love, Numerology & Zodiac Explained
Why a love calculator, a numerology couple match, and a zodiac tool give three different scores for the same two people — and how accurate any of them really are.
IMAGE TOOLSHow to Compress Images Without Losing Quality
A practical guide to shrinking file size while keeping images sharp — plus when to reach for PNG vs. JPEG.
DEVELOPER TOOLSJSON Formatting Best Practices for Developers
Why pretty-printed JSON matters, common syntax errors, and how to catch them before they break your app.
GUIDEFree vs. Paid Online Tools: When Each Makes Sense
Free browser tools cover more use cases than people expect. Here's how to tell when it's worth paying.
COLOR TOOLSWCAG Color Contrast: How the Contrast Ratio Works, Plus AA and AAA Rules
The contrast ratio formula, the 4.5:1, 3:1 and 7:1 thresholds, what counts as large text, and non-text contrast.
DEVELOPER TOOLS10 Browser-Based Tools That Save Developers Time
A roundup of small utilities worth bookmarking — no install, no account, no context-switching.
CONVERTER TOOLSHow Currency Conversion Actually Works (And Why Rates Are Never Truly Live)
Exchange rates on converter tools update regularly, not by the second — here's why that gap exists and when it actually matters.
GENERATOR TOOLSWhat Is a UUID? Format, Versions and Collision Odds
The 8-4-4-4-12 format, version and variant bits, v4 vs v7 for database keys, and when a random number fits better.
CONVERTER TOOLSHow to Calculate Age From a Date of Birth
Years, then months, then days, with worked examples, February 29 birthdays, Excel DATEDIF and Python.
CONVERTER TOOLSPercentage Points vs Percent: What's the Difference?
5% to 10% is 5 percentage points but a 100% increase. Formulas, worked examples and basis points.
DEVELOPER TOOLSUnix Timestamp Explained: Epoch Time, Unix Time and Why 1970
Seconds vs milliseconds, converting in JavaScript, Python, SQL and Excel, leap seconds and the exact 2038 overflow.