Guides
The calculators give you a number. These explain what the number means, where the standard rules of thumb came from, and where they stop working. Every figure is sourced and dated.
How big an emergency fund actually needs to be
"Three to six months" is a slogan, not a number — the figure a household actually needs falls out of its essential monthly expenses, how long gaps really last, and how many incomes stand behind it.
The 50/30/20 budget — what it gets right, and the three situations where it breaks
The 50/30/20 rule is a useful first pass at a budget, but it is measured against after-tax income — and federal household-spending data, metro-level housing costs and the 2026 contribution limits each expose a situation the three percentages cannot handle.
Net worth: what it measures, and the four things it misses
Net worth is one of the easiest personal-finance numbers to calculate and one of the easiest to misread, because the arithmetic hides four things it was never designed to capture.
What an annual salary actually works out to per hour
The standard salary-to-hourly formula divides by 2,080 hours, which quietly assumes nobody ever works an unpaid hour past the 40th — and for anyone who does, the answer is off by dollars an hour, not cents.
What inflation actually does to money that is sitting still
Inflation does not take money away from you; it quietly changes what the same number of dollars can buy, and the official index that measures this is more specific — and more arguable — than the headline suggests.
The 4% rule: where it came from, and what the research actually says now
The best-known number in retirement planning came out of two specific papers with specific assumptions, and almost every argument about it today is really an argument about those assumptions.
How a 401(k) employer match, vesting and the 2026 contribution limits actually work
Four separate rules decide what actually lands in a 401(k) account each year — the deferral limit, the combined limit, the match formula and the vesting schedule — and mixing them up is a common and expensive mistake.
Why starting early beats saving more, and where it stops being true
A ten-year head start can beat three times the contributions, but only if the assumed return clears about 6.1% a year — the crossover for this particular ten-years-versus-thirty comparison — and only if those early contributions are never interrupted.