Savings & Investing Calculators
18 tools for growing money and understanding what you'll keep.
6 groups · No sign-up · Runs in your browser
Investment maths is mostly one idea — compounding — applied to different products. The tools below are organised by what you're actually holding, since the mechanics differ: a CD has a fixed rate and a penalty for early exit, a stock portfolio has variable returns and a tax bill on the way out, and a regular contribution plan behaves differently from a lump sum.
Whatever you're modelling, run the inflation-adjusted return calculator on the result. A 7% nominal return with 3% inflation is a 3.9% real return, and over 30 years that distinction is the difference between a plan that works and one that doesn't.
Understand compounding
The foundation for everything else on this page. The Rule of 72 is the quick mental version; the interest calculator shows the full curve and the simple-versus-compound gap.
Project a portfolio
For lump sums, regular contributions, or both. Dollar-cost averaging and lump-sum investing produce different outcomes in the same market — worth comparing before deciding how to deploy cash.
Certificates of deposit
A ladder staggers maturity dates so you keep access to some cash without giving up the longer-term rates. The penalty calculator tells you whether breaking an existing CD for a better rate actually nets out ahead.
Stocks and dividends
Reinvested dividends are a large share of long-run equity returns, which is why total return and price return diverge so much over decades.
What you actually keep
Nominal returns overstate your gain. Tax and inflation both take a cut, and neither shows up in a headline return figure.
More in this category
Additional tools covering the same ground.
Common questions
Short answers to what people ask most before picking a tool.