Finance Calculators

The finance calculators here work through the arithmetic behind three common money decisions: what a loan actually costs per month, how compound interest grows a balance over time, and whether a retirement savings plan is on track to support a given withdrawal rate. Each result comes with the formula behind it — the standard amortization formula for loan payments, A = P(1 + r/n)^(nt) for compound growth — so you can see exactly which numbers were multiplied, not just trust a black-box output.

Small changes in these inputs compound in ways that aren't always intuitive. An extra percentage point of interest on a 30-year mortgage, or five extra years of compounding before retirement, can change the outcome by a much larger margin than the input change itself suggests. Running the same calculation with a couple of different assumptions — a higher rate, a longer term, an earlier or later retirement age — is often more useful than a single point estimate, and every calculator here makes that easy to do by keeping the formula visible.

None of these results are financial advice. They are mathematical projections based on the numbers you enter, and real loans, markets, and retirement outcomes involve fees, taxes, inflation, and variability that a simplified formula can't fully capture. Use them to build intuition and compare scenarios, and treat any decision with real money at stake as a reason to consult a licensed financial advisor or your loan provider's official disclosures. When you're comparing actual offers, check the lender's stated annual percentage rate (APR) too, since it can fold in fees this calculator doesn't see.