numricaFinancial education from Pedro Roriz — professor, consultant, and founder of Numrica.
Five cards, $18,000 total, minimum payments only: you pay $14,000 in interest over 12 years before the last card clears. This is the math — and the way out.
July 27, 2026 · 7 min read
Saving 20% of $60,000 ($12,000/year) invested at 7% CAGR produces $491,000 in 20 years. Here is the roadmap: order of accounts, asset mix, and the milestones along the way.
July 25, 2026 · 7 min read
On $45,000 in federal loans at 6.5%, the standard 10-year plan costs $15,600 in interest. Income-driven can cut monthly payments but doubles total interest. The full comparison.
July 23, 2026 · 7 min read
Gross yield is misleading. Cap rate ignores financing. Cash-on-cash return is what you actually pocket. Here is how to run all three calculations with a real $350,000 property example.
July 21, 2026 · 8 min read
Home equity loans give you a fixed rate on the full amount. HELOCs give you a revolving line at variable rates. For a $30,000 kitchen reno, one is clearly cheaper — but it depends on timing.
July 21, 2026 · 6 min read
Net worth = assets minus liabilities. But what counts, how often to measure, and which benchmarks to compare against are not obvious. A practical guide for building and tracking it.
July 19, 2026 · 6 min read
Retire in 10 years: save 66% of income. In 15 years: 50%. In 20 years: 40%. These are not aspirational figures — they are the output of the 4% rule applied to standard spending multiples.
July 17, 2026 · 7 min read
Over 6 years of driving, leasing typically costs $4,000–$8,000 more than buying. But if you lease into a new car every 3 years, the math can flip depending on depreciation.
July 17, 2026 · 7 min read
50% needs, 30% wants, 20% savings. The rule was designed for median incomes in the 1990s. Here is why it breaks for high earners, high-cost cities, and heavy debt loads.
July 14, 2026 · 6 min read
Factor in commute time, work clothes, lunches, and job-related stress spending and your $80,000 salary might net $28/hour. This calculation changes how you think about purchases.
July 15, 2026 · 6 min read
Save 10% and work 40 years. Save 50% and work 17 years. The relationship between savings rate and retirement age follows a precise mathematical curve — and the gains accelerate.
July 13, 2026 · 7 min read
HYSAs now pay 4.5–5%. 12-month CDs offer 4.7–5.1%. The yield difference is narrow — the real distinction is liquidity vs rate lock. How to choose based on your timeline.
July 12, 2026 · 6 min read
At 3% inflation, $10,000 in a 0.5% savings account loses $250 in real purchasing power every year. After 10 years you have $10,500 nominal but $7,700 in real value.
July 11, 2026 · 6 min read
At 30: 1x salary. At 40: 3x. At 50: 6x. At 60: 8x. These Fidelity benchmarks assume a specific savings rate and return. Here is what the math looks like behind each target.
July 10, 2026 · 7 min read
Divide 72 by your return rate to find how many years to double your money. At 8%, that is 9 years. At 12%, just 6. A simple mental model that reveals compounding in one step.
July 9, 2026 · 5 min read
The 3-6 month rule is a starting point. A freelancer with variable income needs 9 months. A dual-income household with stable jobs might need only 2. The right number for your situation.
July 8, 2026 · 6 min read
If your tax rate is higher now than in retirement, Traditional wins. If lower now, Roth wins. Here is how to estimate which camp you are in — with actual scenarios.
July 7, 2026 · 7 min read
Over 20 years, a 1% fee difference reduces your terminal wealth by 18%. That is why 85% of active funds underperform their index benchmark after fees.
July 6, 2026 · 6 min read
Starting at 25 vs 35 with the same contributions produces a $340,000 difference by retirement. That is not a rule of thumb — it is compound interest doing its work.
July 5, 2026 · 6 min read
Studies show lump sum investing beats DCA about two-thirds of the time. But the psychological risk of investing everything the day before a crash is real. The honest tradeoff.
July 4, 2026 · 7 min read
One mortgage point costs 1% of the loan and buys roughly 0.25% off your rate. Whether that is worth it depends on one number: how long you plan to stay.
July 3, 2026 · 6 min read
On a $350,000 loan, the 30-year costs $232,000 more in interest than the 15-year. But the monthly payment difference is $600. Here is the real tradeoff.
July 2, 2026 · 6 min read
The break-even rule: if closing costs are $4,000 and you save $200/month, you break even in 20 months. But that calculation misses three critical variables.
July 1, 2026 · 7 min read
At 3% mortgage rate, investing wins by a wide margin. At 7%, the answer is far less obvious. How to run the actual numbers for your situation.
June 30, 2026 · 7 min read
Lenders approve mortgages up to 43% DTI. Financial planners recommend 28%. The gap between those two numbers is your financial cushion — or lack of it.
June 29, 2026 · 7 min read
$50,000 in mixed debt — student loans, car loan, credit cards — feels impossible. Here is how to structure payments so the last dollar is gone in under 4 years.
June 28, 2026 · 9 min read
Most lenders reject borrowers with a DTI above 43%. Here is how to calculate yours, what each range means, and the fastest ways to bring it down.
June 27, 2026 · 6 min read
A 0% APR balance transfer can save $1,200 in interest — or cost $300 in transfer fees. How to calculate whether the offer makes sense before you apply.
June 26, 2026 · 6 min read
A 760 vs 680 score on a $400,000 mortgage costs $80,000 more in interest over 30 years. Here is exactly what moves the needle — and how fast.
June 25, 2026 · 7 min read
The average American with credit card debt carries $6,000 across multiple cards at 22% APR. A structured plan to eliminate it — with the exact order, amounts, and math.
June 24, 2026 · 8 min read
A $5,400 credit card balance at 24.99% APR, paid on minimums only, costs you $4,300 in interest before it's gone. Here is the number that actually matters.
May 21, 2026 · 6 min read
Um saldo de R$5.000 no rotativo a 10% ao mês, pago apenas no mínimo, pode custar R$10.000 em juros antes de ser quitado. Aqui está a matemática — e o que R$200 a mais por mês realmente fazem.
21 de maio de 2026 · 6 min de leitura
Most people with three debts do not know which to pay first. That indecision has a measurable cost — between 20% and over 100% of the original debt balance in extra interest.
May 21, 2026 · 7 min read
A maioria das pessoas com três dívidas simultâneas não sabe qual pagar primeiro. Essa indecisão tem um custo que pode representar entre 20% e mais de 100% do valor original das dívidas.
21 de maio de 2026 · 7 min de leitura
Most borrowers choose their mortgage rate type based on the initial monthly payment. That is the wrong basis for a 25-year decision. Three scenarios, one simulation.
May 21, 2026 · 7 min read
A maioria das pessoas escolhe o regime de taxa do crédito habitação com base na prestação inicial. Essa é a decisão errada.
21 de maio de 2026 · 7 min de leitura