How this calculator works
The calculator treats your monthly contributions as an annuity — a series of equal payments made at regular intervals — and grows each contribution with compound interest. It uses the standard future value of an annuity formula:
FV = P × [((1 + r)n − 1) ÷ r] × (1 + r)
Here, P is your monthly investment, r is the monthly rate (your annual return divided by 12), and n is the total number of monthly contributions. The extra (1 + r) factor accounts for contributions being invested at the beginning of each month. The calculator converts your annual percentage into a monthly rate automatically, so you never have to do that division yourself.
A worked example
Suppose you invest $500 every month for 10 years at an expected annual return of 10%. Your monthly rate is 10 ÷ 12 = 0.833%, and you make 120 contributions. Plugging those into the formula gives a projected maturity value of about $103,276.
Your total contributions are $500 × 120 = $60,000, so the estimated gains are $103,276 − $60,000 = $43,276. Notice that returns account for more than 40% of the final value — that is compounding doing the heavy lifting over a decade.
What the results mean
Total invested is simply your monthly amount multiplied by the number of months — the money that actually came out of your pocket. Estimated gains are the growth on top of that, driven by your assumed return rate. Maturity value is the sum of both: what the calculator projects your investment could be worth at the end of the period.
The year-by-year table is worth studying closely. In the first few years, the value grows mostly because you keep adding money. In later years, growth increasingly comes from returns on accumulated returns. That shift is the clearest illustration of why time in the market matters so much.
Practical tips
- Start with what you can sustain. A smaller monthly amount you keep up for 15 years beats a larger one you abandon after two. Consistency is the input that matters most.
- Increase contributions as income grows. Raising your monthly amount by even a small percentage each year can meaningfully lift the final value without changing your return assumptions.
- Be honest about the return rate. Higher assumed returns make the projection look better but less reliable. Run the numbers at 8%, 10%, and 12% and plan around the middle or lower case.
- Give it time. The same $500 monthly contribution at 10% grows to roughly $103,000 in 10 years — but to about $380,000 in 20. Doubling the time more than triples the outcome.
Limitations
This calculator produces estimates, not guarantees. It assumes a constant annual return, but real investments fluctuate — sometimes sharply — and fees, taxes, and inflation all reduce real-world outcomes. It also ignores the possibility of missed contributions, which is common over multi-year horizons. Use the results for planning and comparison, and consider speaking with a qualified financial professional before making investment decisions.
Frequently asked questions
What is a SIP?
A Systematic Investment Plan (SIP) is a method of investing a fixed amount of money at regular intervals — usually every month — into an investment such as a mutual fund. Instead of investing a large lump sum at once, you contribute smaller amounts over time, which spreads out your entry points and makes investing more affordable.
How accurate is this SIP calculator?
The calculator applies the standard future-value-of-annuity formula to your inputs, so the arithmetic is exact. The estimate itself, however, depends on the return rate you enter — and real investments never return a perfectly constant rate. Treat the result as a planning illustration, not a prediction of what you will actually earn.
Does the calculator assume investments are made at the start or end of the month?
It assumes each monthly contribution is invested at the beginning of the month, which is the standard convention for SIP calculations. This gives each contribution one extra month of compounding compared with end-of-month timing, so the result is slightly higher than an end-of-period calculation.
What return rate should I enter?
Enter a realistic long-term average for the kind of investment you have in mind — for example, many long-term equity investors use 8–12% as a planning assumption, while conservative fixed-income products use lower figures. Try several rates to see how sensitive your outcome is to this one input; it matters more than almost anything else.
Why does the growth accelerate in later years?
That is compounding at work. In the early years, most of your account value is your own contributions. Later, the returns earned on earlier returns become a larger share of the total — so the same monthly contribution produces faster overall growth. This is why starting early matters more than investing large amounts later.