This grows a starting amount and optional regular contributions forward through time at a given rate of return — the same compounding this site’s compound-interest calculator documents, extended to combine a lump sum with ongoing deposits.
How it works
Future value
FV = PV × (1+r)ⁿ + PMT × (((1+r)ⁿ − 1) ÷ r)
A single lump sum left to grow, and a stream of regular deposits with no starting balance, are both special cases of this one formula.
How to use this calculator
- Enter any starting amount.
- Add a monthly contribution if you’re investing regularly, not just once.
- Enter the expected return and time horizon.
Frequently asked questions
How is this different from the compound interest calculator?
Nearly identical mechanics — this one is framed around growing toward a future target with an optional starting balance and contributions together, useful for retirement or savings-goal style projections.
Does contributing earlier really matter that much?
Yes — money contributed earlier has more time to compound, so identical total contributions made earlier in the timeline produce a meaningfully larger final balance than the same contributions made later.
What return rate should I assume?
There’s no universally correct figure — it depends on what you’re actually invested in and its own risk and historical performance. This calculator computes correctly for whatever rate you enter; it doesn’t recommend one.
Why does starting balance and contributions grow at different effective paces?
The starting balance compounds for the full period from day one. Contributions made partway through the timeline have less time to compound — the formula for the contribution stream accounts for this directly rather than treating every dollar as if it started on day one.
Is this a guarantee of what I’ll actually have?
No — it’s a projection at one assumed constant rate. Real returns vary year to year rather than compounding smoothly, so treat this as an illustration of the mechanics, not a guaranteed outcome.
