Guides

How Is a Loan Payment Calculated? The Formula With a Worked Example
How is a loan payment calculated? The amortizing formula US lenders use, worked through on a $250,000 mortgage, and what changes the result.
How CD Interest Is Calculated: Compounding and APY Explained
How CD interest is calculated: the compound formula, rate versus APY, daily and monthly compounding compared on $10,000, early withdrawal penalties and taxes.
How a Savings Plan Grows: The Math Behind Monthly Deposits
How a savings plan grows: the deposit-by-deposit math behind $500 a month at 4%, why early deposits earn most, and what the interest really adds over ten years.
Extra Mortgage Payment: Shorten Term or Lower Payment?
Extra mortgage payment: shorten the term or lower the payment? The same $20,000 under both options, the interest each saves, and when each one fits.
EIN Number Format: What the 9 Digits Mean
EIN number format: the XX-XXXXXXX layout, what the two-digit prefix means, why there is no check digit, EIN versus SSN versus ITIN, and where it appears.
CD vs High-Yield Savings: Which Is Better for Your Money?
CD vs high-yield savings: a locked rate against a variable one, $10,000 compared over one, three and five years, the penalty risk, and when each wins.
Amortization Schedule Explained: Why Early Payments Are Mostly Interest
Amortization schedule explained with a $250,000 mortgage: how each payment splits, why year one is 72% interest, and how to read the table.
Add-On Interest vs APR: Why 8% Add-On Costs Like 14.5%
Add-on interest vs APR: how an add-on rate charges interest on the full amount for the whole term, why 8% add-on equals 14.5% APR, and where it still appears.
Numbers to Words Rules for Dollars: Hyphens, “And”, and Large Amounts
Numbers to words rules for dollars: hyphens in twenty-one to ninety-nine, where "and" goes, thousands and millions, zero cents and legal documents.
When to Pay Off Your Mortgage Early (and When to Invest Instead)
When to pay off your mortgage early: the rate-versus-return test, the tax deduction, emergency funds and timing, with a $20,000 example worked both ways.