The most important thing most people can do with investments is simple: start early and contribute consistently. This calculator makes the payoff of that visible by projecting how a lump sum plus regular contributions grow over time.
Compounding, the eighth wonder
When returns are reinvested, they earn returns of their own. Over decades this turns a fairly modest stream of contributions into a much larger sum. The formula separates the lump-sum growth from the contributions so you can see exactly how each part contributes to the whole.
Time beats timing
The single biggest lever in the projection is the number of years, not the rate. That's why starting early dominates trying to pick the perfect moment to invest — you can't buy back time, but compounding can make the most of the time you have.
The honest projection
A projection is only as good as its assumptions. Real returns are lower than headline averages once you subtract fees and taxes, and they're never guaranteed. The value of this math is planning — setting realistic expectations so you save enough to reach your goal.
Frequently asked questions
Future value = initial × (1 + rate)ⁿ plus the accumulated monthly contributions with their compounding. This calculator does exactly that from your inputs.
Yes — contributions made earlier compound for longer. Regular, automatic investing (dollar-cost averaging) both smooths volatility and keeps you consistently in the market.
Historical broad stock-market averages have been around 7% above inflation, but it varies hugely. Use conservative assumptions and consider fees and taxes.