Guides
Every guide we have published, newest first. Each one is written around specific numbers rather than general principles.
30 guides
A $2,000 credit and a $2,000 deduction are not remotely the same money. The exact math of each, a full worked return from income to bill, and where phase-outs and refundability change the answer.
A broken washing machine or fridge forces a fast decision with real money on the line. Work the repair-or-replace math with actual numbers: expected remaining life, the 50% rule and where it fails, energy savings, and total cost of each path.
A large tax refund feels like a win, but it usually means you lent the government money all year at 0% interest. Work the actual cost with numbers, learn where to adjust withholding, and see when a big refund is fine anyway.
Store financing that says 'no interest for 12 months' can bill you a year of interest overnight. Here is exactly how deferred interest works, with the math of a $1,800 laptop.
Car repairs, holidays, vet bills — the expenses that wreck a budget are the predictable ones nobody budgets for. Sinking funds fix that with simple division; here's the full math.
Wrong balances, mystery accounts, debts that will not die: how to find errors on your three credit reports and dispute them until they are actually fixed.
The checkout counter pitch, decoded with arithmetic: what an extended warranty must pay out for it to beat simply self-insuring, and the few cases where it genuinely does.
The minimum payment is engineered to keep the balance alive, not to end it. A full worked example at a 22.9% APR shows 125 years of payments and $92,000 of interest — and the two moves that collapse the timeline.
Paying insurance monthly can cost 5–15% more per year. A worked example on a $1,200 policy shows when the installment fee wins anyway — and the exact break-even fee rate where it does not.
On a $350,000 30-year loan, the rate gap between credit tiers is worth six figures over the life of the mortgage. Here is the tier-by-tier arithmetic, where the cliffs are, and when chasing a higher score stops paying.
Paying off a 22.9% credit card is a guaranteed 22.9% return; investing at an expected 7% is not guaranteed at all. Running both scenarios side by side shows exactly where the crossover is — and why the answer is mostly about interest rates.
The entire Roth-versus-traditional question reduces to one comparison: your marginal tax rate today versus your effective rate in withdrawal. Here is the algebra that proves it, the dollar outcomes at each rate pair, and where the equal-tax theorem breaks.
Comparing a mortgage payment to rent flatters buying, because most of what ownership costs hides outside that payment. Here is a full break-even model with every number shown.
A $500,000 term policy and a $500,000 whole life policy insure the same life. The difference is roughly $109,000 in premiums over 20 years. Here is what that money actually returns.
A dollar-for-dollar employer match is a 100% return before your money is invested anywhere. Running the numbers on a $62,000 salary shows exactly what contributing under the match threshold gives up.
On a $350,000 home with 20% down, closing costs and prepaids add about $10,900 on top of the down payment. Here is the line-by-line math, and which parts you can actually negotiate.
A family of three on a major carrier's premium unlimited plan pays about $160 a month. The same three lines on an MVNO run about $75 — with real trade-offs you can test before committing.
Rules of thumb like "ten times your salary" hide the real calculation. A 35-year-old with a $240,000 mortgage and two kids lands near $1 million of coverage. Here is the worksheet.
A CD ladder usually pays more than a savings account — but not always. We run $15,000 through both over three years, including the rate-cut scenario where the ladder wins big.
"Just raise your deductible" is the oldest money advice on the internet. Here is the actual break-even math for $500 vs $1,000 vs $2,500, including the expected-value version and the two cases where it backfires.
An extra $100 a month on a $340,000 mortgage at 6.25% cuts 3.5 years and $58,000 of interest. Full amortization tables for $100, $200, $400 and the 13th-payment trick — plus when investing beats prepaying.
A dollar-for-dollar walkthrough of the 2025 US federal brackets: what a marginal rate means, what a $58,000 salary actually pays, and the arithmetic behind the "a raise pushed me into a higher bracket" myth.
A $6,200 balance costs $2,278 in interest at 22.9% APR — or $186 with a balance transfer fee, if the payoff actually happens inside the promo window. Every number, including the trap that turns the fee into $8,806.
A $18,000 used car financed at 8.2% costs $366.70 a month — and about $501 a month on top of that. Fuel, insurance, maintenance, tires, depreciation and registration, line by line, so the budget matches reality.
Same $14,000 of debt, same $750 monthly budget: the avalanche saves $422 in interest, the snowball closes two accounts sooner. Here is the month-by-month arithmetic behind both, including what minimum-only payments really cost.
A 4.00% APY account pays $400 a year on $10,000; a typical branch-bank rate pays $46. The full math on compounding, taxes, variable rates, and when a savings account is the wrong tool entirely.
Utilization drives 30% of a FICO score and resets every month. The per-card and overall math, why the statement date matters more than the due date, and the 30-day plan before a big application.
Most budgets fail in week three, not week one. Here is a monthly system built around irregular income, annual bills and the spending you are not going to stop doing.
The average household now pays for far more recurring services than it can name. A practical audit, plus the cancellation traps that keep charges running after you think you have stopped them.
Three to six months of expenses is the standard answer. For most people it is either the wrong number or the right number for the wrong reason. Here is how to size it properly.