Investment Calculator

A starting balance grows using compound interest, FV = P × (1 + r)^n, and recurring contributions grow using the future value of an annuity formula. The calculator converts your nominal annual return and compounding frequency into the exact rate for each contribution period, then projects the balance forward year by year.

It flips the usual question around: instead of telling you the ending balance for a contribution you choose, it finds the smallest recurring contribution that reaches your stated goal by the target year, given your starting amount, return, and compounding. It uses the same growth formula, searched by bisection rather than solved algebraically.

It answers 'what average annual return would I need to reach my goal' given your starting amount, contributions, and years. It's a useful reality check — if the required return is far above typical long-term market averages, the goal may need a longer timeline, a bigger contribution, or a lower target instead.

This happens only when the goal exceeds what's mathematically possible within the search range: for return rate, that means even 200% annual growth wouldn't get there; for years, it means 100 years (the calculator's cap) isn't enough at the rate you entered. Try increasing the contribution, starting amount, or time horizon, or lowering the goal.

They share the same underlying growth engine. The compound interest calculator always projects forward from your inputs. This investment calculator adds the ability to solve backward — for the contribution, rate, starting amount, or time needed to hit a specific goal.

It has a modest effect. Contributing at the start of each period gives that money one extra period of growth compared with contributing at the end, so 'start' timing produces a slightly higher ending balance for the same contribution amount — the gap grows with higher rates and more periods.

This calculator doesn't recommend a rate — that depends on your specific investments, time horizon, and risk tolerance. Many long-term financial plans use a range of assumptions and stress-test several scenarios rather than relying on a single number; consider trying a few different rates here to see how sensitive your plan is.

The projection itself uses the nominal return you enter. If you set an inflation rate under Advanced, results reflect it only insofar as you've already chosen a return net of inflation, or you can compare the nominal ending balance against your own inflation expectations separately.

Yes. Under Advanced, 'Annual contribution increase' grows your periodic contribution by a fixed percentage every year, which is useful for modeling a contribution that rises alongside a salary increase.

It models the underlying growth math the same way, but it doesn't account for employer matches, contribution limits, or tax treatment. For those, use the 401(k) or Roth IRA calculators, which build on the same growth engine with those specifics included.