Short answer: enter what you started with, what you added each month, how long it ran, and what it’s worth now. You get your total return and your annualized (money-weighted) return — the honest per-year number for money you added over time. Example: $10,000 started, $200/month for 10 years, ending at $45,000 → you put in $34,000, gained $11,000 (32.4%), which annualizes to about 4.29% a year.
| Total you put in | — |
| Total gain | — |
| Total return on money invested | — |
See the full breakdown
Educational only — not financial advice. The annualized figure is a money-weighted return (the same idea as IRR): it assumes your monthly additions were equal and spread evenly, and solves for the single steady monthly rate that connects what you put in to what you ended with. If your deposits were lumpy, your true personal rate will differ. Past return figures never predict future results.
How this calculator works
Total return is simple: (final − total invested) ÷ total invested. The annualized figure is harder, because money added in year 9 didn’t have 10 years to grow — a plain compound-growth formula would lie. So the calculator solves for the single steady monthly rate that, applied to your starting amount and each monthly addition, lands exactly on your final value (a money-weighted return, the same concept as an internal rate of return), then converts it to an annual rate. It finds that rate by bisection — narrowing the range 200 times — not by approximation formulas.
Worked example
- Start $10,000, +$200/mo, 10 years, final $45,000 → invested $34,000, gain $11,000, total return 32.35%, annualized 4.29%.
- Lump-sum check: $5,000 → $9,000 in 5 years, nothing added → annualized 12.47% (matches the textbook CAGR formula (9000/5000)^(1/5) − 1 exactly).
- Modest case: $10,000 + $100/mo for 5 years ending $12,000 → invested $16,000, total return -25.00%, annualized -7.01%.
FAQs
Why is my annualized return different from what my brokerage shows? Brokerages usually show a time-weighted return (the fund’s performance, ignoring your deposits). This tool shows a money-weighted return (your performance, including your timing). Both are real; they answer different questions. Can this handle losses? Yes — the solver works for negative returns too, down to near-total loss. I added money unevenly. Is this still right? It’s an even-deposits approximation, labeled as such. For an exact figure you’d need each deposit’s date (that’s a full XIRR calculation).
Sources: Investor.gov compound interest calculator (method) Figures last verified Report a wrong number