Financial Calculators

Money calculations are simple arithmetic applied repeatedly, and the repetition is what makes them hard to do in your head. Interest compounds, payments amortise, and small differences in rate or term produce large differences in total cost. These calculators show the totals alongside the monthly figures, because the monthly number alone hides how much a longer term actually costs.

Two ideas explain most of it. Compounding means interest earns interest, so the frequency matters as well as the rate — the same nominal rate compounded monthly returns more than compounded annually, which is why APY and APR are different numbers. Amortisation means an early payment is mostly interest and a late one is mostly principal, which is why overpaying early on a loan saves disproportionately more than overpaying late.

Read the rate carefully. A quoted rate is usually annual, so a monthly calculation divides it by twelve, and a daily one by 365. Fees folded into APR make it a better comparison figure than the headline rate, and tax treatment can outweigh the rate entirely — which is the whole point of the retirement calculators here, where the same contributions produce very different outcomes depending on whether the account is taxed going in or coming out.