The Blog
Practical writing on compound interest, debt, and long-term planning. Each post includes worked examples and links to the relevant calculator.
The Rule of 72: How to Estimate Compound Growth in Your Head
A 300-year-old approximation that lets you mentally compute how long it takes money to double at any rate. Surprisingly accurate up to about 20%.
Read post →Simple vs. Compound Interest: The Gap That Builds (or Drains) Wealth
The difference looks tiny at first and then becomes enormous. A side-by-side walk-through with worked numbers and where each type shows up in real products.
Read post →How Amortization Works: Why Your Mortgage Payment Is Mostly Interest for Years
Amortization front-loads the interest: on a 30-year 6% mortgage, 83% of your first payment is interest. Here's the schedule, and how extra payments beat it.
Read post →Dollar-Cost Averaging vs Lump Sum: The Math Says You're Being Too Careful
Lump-sum investing beats dollar-cost averaging roughly two-thirds of the time. Here's the math, and why spreading out is still the right call for many.
Read post →CAGR vs Average Return: Why Your “10% Average” Was Really 8%
Average return is the arithmetic mean; CAGR is the geometric mean. Volatility drags the real return below the average. Here's the formula and how big the gap gets.
Read post →APR vs APY: The Difference That Compounds Into Real Money
APR is the stated rate; APY is what you actually earn or pay after compounding. Here's the formula, how big the gap gets, and how to convert between them.
Read post →Debt Snowball vs Avalanche: Which Debt Payoff Method Actually Wins
Snowball pays the smallest balance first for motivation; avalanche pays the highest rate first to save interest. Here's the math, a worked example, and how to choose.
Read post →How Much Should Your Emergency Fund Be? The Real Answer
The 3-to-6-month rule is a starting point, not a law. Here's how to calculate your emergency fund from essential expenses, income stability, and risk.
Read post →How to Calculate ROI (and Why the Number Alone Is Meaningless)
ROI = (Gain − Cost) ÷ Cost. But without a time horizon, ROI is meaningless. Learn the formula, the annualized version, and the five mistakes that inflate returns.
Read post →The 4% Rule: How Much You Need to Retire (and the Risk That Breaks It)
The 4% rule says withdraw 4% yearly, so retire with 25× your annual spending. But the real risk is sequence of returns, not average return.
Read post →Retire by 50: A 20-Year Plan
Retiring by 50 when you're starting at 30 gives you exactly a 20-year runway. It’s entirely doable, but it requires shifting from standard financial advice to aggressive, intentional wealth-building.
Read post →What's coming
We're working on more posts: why a 1% mortgage rate cut is worth more than you think, the math of dollar-cost averaging in volatile markets, and a deep dive on real (inflation-adjusted) returns. Tell us what to write next.