Money & Finance
Budgeting, borrowing, interest and pay — the arithmetic behind the decisions that cost the most.
Future cost = amount × (1 + rate)^years — one formula, but the rate you assume moves the answer more than the years do. Three worked projections with the arithmetic shown.
FIRE number = annual spending × 25 — the inverse of the 4% withdrawal rule, in one multiplication. Three worked spending levels, and what cutting spending actually does to the target.
Gross = rate × regular hours + rate × multiplier × overtime hours — one formula, but the multiplier alone can swing a week's pay by real money. Two worked weeks, with the arithmetic shown.
The bigger package isn't automatically the better price — dividing price by quantity is the only way to know for sure. Three worked comparisons, including one where the "value" size loses.
Assets minus liabilities — one subtraction — but it's the only number that tells you whether you're actually getting ahead. Two starting snapshots and a year-later check-in, all with real arithmetic.
The bigger dollar profit isn't always the better deal — return on investment puts two different-sized bets on the same footing. The formula, a side-by-side comparison, and what a loss looks like in the same math.
The same stated rate produces a different real number depending on how often it compounds. Here's the formula, two worked examples — a savings account and a credit card — and why the gap matters more than the sticker rate.
The target is one multiplication — essential monthly expenses times months of cushion — but the months figure is where the real decision lives. Here's the formula and two worked examples showing how much that choice moves the target.
Not every loan compounds. Here's the formula behind flat-rate interest, a real worked example, and exactly how many dollars compounding would have added to the same loan.
One guideline decides the rent ceiling most apartment hunts start from: no more than 30% of gross income. Here's the formula, a real example, and why it doesn't know about your other debts.
One ratio decides whether a mortgage application clears the first hurdle, often before your credit score gets a look. Here's the formula, the bands lenders use, and how a single new car payment can flip “Good” to “Caution”.
A salary quotes one number a year, but the hourly rate behind it depends entirely on how many hours you actually work — and for exempt employees, extra hours are a hidden pay cut, not overtime pay. Here's the math, and how to compare two offers fairly.