Guides
Practical explainers written to go with our tools—not thin glossaries. Each guide walks through concepts with worked numbers, common mistakes, FAQs, and links back to the matching free calculators or converters.
Start here when you want the “why,” then open a tool when you need the answer. No account required; tools run in your browser where possible.
Percentages and Discounts: A Practical Guide
Learn percentage of, percent change, multi-discount stacking, tax, and tips—with worked dollar examples and free calculators.
2 related tools · Math & Numbers
Mortgage and Loan Basics: What You Need to Know
Estimate mortgage and loan payments from principal, rate, and term—plus tax, insurance, and interest trade-offs with free calculators.
3 related tools · Money & Finance
Unit Conversion Basics: Length, Weight, and Temperature
Convert metric and imperial length, mass, and temperature with exact factors, worked examples, and free online converters.
3 related tools · Unit Converters
Word Counts and Text Tools: Hit Your Limits and Clean Copy
Meet word and character limits, estimate reading time, and clean copy with counters, case tools, and find-and-replace workflows.
3 related tools · Text Tools
BMI and Health Metrics: What They Mean and When to Use Them
Understand adult BMI categories, limits of the metric, and how BMR/TDEE estimates work—informational tools, not medical advice.
2 related tools · Calculators
Hashes and Encoding: When to Use Hash, Base64, and URL Encode
Learn when to use SHA hashes, Base64, and URL encoding—with checksum examples and browser tools that keep data local.
3 related tools · Developer Tools
Using Date and Time Tools: Epoch, Time Zones, and Conversions
Convert Unix epoch timestamps and time zones correctly—seconds vs milliseconds, DST pitfalls, and scheduling examples.
2 related tools · Date & Time
Color Contrast and Accessibility: WCAG Basics
Meet WCAG AA/AAA contrast ratios for text, fix brand-color failures, and convert hex/RGB/HSL with practical design checks.
2 related tools · Color Tools