Finance Calculator
Project an ending balance with compound growth, optional monthly deposits, and your choice of compounding frequency.
Plan inputs
Ending balance:
Starting: · Total contributed: · Growth (interest):
Lump sum plus contributions
This calculator combines two growth sources: your starting amount compounding on its own, and a stream of regular monthly contributions that each start compounding from the moment they're deposited. Contributions made "at the beginning" of the month get one extra compounding period compared to contributions made "at the end," which is why the timing option produces slightly different results.
Frequently asked questions
Why does contribution timing make a difference? A deposit made at the start of the month earns a full month of growth before the next deposit; a deposit at the end of the month earns growth starting only from the following period — over many years, this small timing difference compounds into a modest but real gap in the ending balance.
How much of my ending balance is actually "growth"? The result breaks this out directly — "Total contributed" shows your own money in (starting amount plus all deposits), and "Growth (interest)" shows how much the ending balance exceeds that, which is the value compounding added on top of your contributions.
What return rate should I assume? That depends on what you're investing in — savings accounts and CDs earn much less than diversified stock portfolios historically have, so use a rate consistent with the actual investment you're modeling.