Guides
The calculator shows you a number. These guides explain where it comes from — with worked examples, comparison tables and scenarios you can open in the calculator with one click.
- Compound interest formula explained – with worked examplesWhat each part of A = P × (1 + r/n)^(n·t) does to the result, how to solve it for rate or time, and where a single formula stops being enough.Open →
- Monthly vs. yearly compounding – what the frequency is worthHow much more monthly compounding pays than annual, why the gap has a ceiling, and how to compare nominal against effective rates.Open →
- How much to save per month – a savings plan that holds upWhat different monthly amounts add up to over twenty-five years, what waiting five years costs, and when interest overtakes your own contributions.Open →
- Withdrawal plan – how long a portfolio lastsFour withdrawal rates on the same portfolio, where the 4 % rule comes from, and why the order of the years matters once you are taking money out.Open →
- Inflation and real returns – what your money will actually buyThe exact way to turn a nominal return into a real one, what 2 % inflation costs over thirty years, and how to keep a whole plan in today's money.Open →
- The rule of 72 – doubling time in your headDivide 72 by the interest rate and you have the doubling time. How accurate that is, where the 72 comes from, and the version worth carrying around.Open →