Guides
Original articles that explain the ideas behind our calculators — written so you can make better decisions with the numbers.
These guides are separate from the interactive tools. Each one adds context you will not get from a form alone: definitions, comparisons, pitfalls, and links to the matching calculator when you want to run the numbers yourself.
Mortgage payment vs PITI: what your quote really includes
Learn why a calculator’s principal-and-interest figure is usually lower than the monthly housing cost a lender discusses.
Read guideBMI limitations: when the number misleads
Body Mass Index is a screening tool, not a diagnosis. See who it fits poorly and what else to consider.
Read guidePercent change vs percentage points
A common mix-up in news, finance, and grades — with clear examples and when to use each.
Read guideMetric and imperial conversions people actually need
Exact factors for length, mass, distance, and temperature, plus rounding tips for travel and school.
Read guide