Mutual Fund Calculator

Two ways money goes in

Money reaches a mutual fund one of two ways. Either you have a sum now and put it in at once, or you put a fixed amount in every month for years.

The second is what India calls a Systematic Investment Plan, and it has become the default way most people invest, largely because it fits how salaries arrive.

This tool does both. Pick the mode from the dropdown, fill in three numbers, and it returns the value at maturity.

The two modes look like the same calculation with a different input. They are not, and the difference is more interesting than it first appears. There is a section below on how they compound, and another on why the order of good and bad years wrecks one of them and leaves the other untouched.

The dropdown decides which fields you see

Start at the top. Investment form switches between Systematic Investment Plan and One-time investment, and the amount field changes to match.

1. Monthly investment, if you chose SIP. What leaves your account each month.
2. Investment amount, if you chose one-time. The single sum.
3. Expected annual return, as a percentage. Your assumption, not anybody's offer.
4. Investment period, with a dropdown for months or years. Sixty months and five years both work and give the same answer.

Press Calculate and you get one figure: the investment amount at maturity.

Since it returns the maturity value only, do one subtraction yourself. For a SIP, your total invested is the monthly amount times twelve times the years. Take that off the maturity figure and you have what the returns actually contributed, which is usually the number people find most striking.

The SIP formula, including the bit at the end

For a monthly plan the tool uses the standard SIP relation:

M = P × [((1 + i)ⁿ - 1) ÷ i] × (1 + i)

P is your monthly amount, i is the monthly rate, which is your annual rate divided by twelve, and n is the total number of months.

The part in square brackets is the ordinary future value of a series of payments. The interesting bit is the × (1 + i) hanging off the end, which most explanations skip past without comment.

That factor exists because your instalments go in at the start of each month rather than the end. Every contribution therefore gets one extra month of growth compared with the plain version of the formula. In the language of financial mathematics this is an annuity due rather than an ordinary annuity.

How much is it worth? On five thousand a month at twelve percent for ten years, the start-of-month version comes to 11,61,695 and the end-of-month version to 11,50,193. A difference of 11,502, which is exactly one month of growth on the whole balance, or one percent.

Small, but it is the reason two SIP calculators can disagree by about a percent on identical inputs. If you compare our figure against another tool and find a gap of roughly that size, this is where it lives. The start-of-month convention is the right one for how SIPs are actually collected.

The one-time mode is much simpler. Amount multiplied by one plus the annual rate, raised to the number of years.

Five thousand a month for ten years

Monthly investment 5,000, expected return 12 percent, period 10 years.

The monthly rate is 12 divided by 12, which is 1 percent. The number of months is 120.

Working the brackets: 1.01 raised to the power of 120 is about 3.3004. Take away 1 and divide by 0.01, which gives 230.04. Multiply by 1.01 for the start-of-month factor and you get 232.34.

Then 5,000 × 232.34 = 11,61,695.

Now the subtraction the tool leaves to you. You invested 5,000 a month for 120 months, which is 6,00,000. So the returns contributed 5,61,695, very nearly as much again as you put in.

Stretch it to twenty years and the shape changes completely. You invest 12,00,000 and finish with 49,95,740, so the returns contribute 37,95,740, more than three times what you put in.

Doubling the years did not double the outcome, it more than quadrupled it. That is compounding, and it is the entire argument for starting a SIP earlier rather than starting a larger one later.

The two modes compound differently

Something worth knowing before you compare the two modes against each other, because it is not signposted anywhere in the interface.

The SIP mode works in months. It divides your annual rate by twelve and applies it twelve times a year. Twelve percent handled that way is an effective 12.68 percent annually, because the interest earned in January starts earning in February.

The one-time mode works in years. It applies your annual rate once a year, so twelve percent means twelve percent.

On a single sum of 1,00,000 over five years at a headline twelve percent, that difference is worth about 3 percent: 1,76,234 under annual compounding against 1,81,670 under monthly.

Neither is a mistake. Both match how the respective products are conventionally quoted in India, where lump sum growth is discussed as a compound annual growth rate and SIP returns are worked monthly. Every major Indian calculator does the same thing.

It does mean one specific comparison needs care. If you want to test putting six lakh in at once against six lakh spread over ten years as a SIP, the two answers are not on quite the same compounding basis, and a small part of any gap is convention rather than substance. For a like-for-like lump sum projection on the annual convention, the lumpsum calculator does exactly that and shows the invested amount and the earning separately.

The order of the good years matters, and only for one mode

This is the most important thing on the page and almost no projection tool mentions it.

Both modes assume your return arrives in identical annual slices. Twelve percent, twelve percent, twelve percent, for as long as you asked. Real markets do nothing of the sort. They deliver thirty percent one year and lose fifteen the next, and the average only emerges over a long stretch.

The question is whether that matters, and the answer is different for the two modes.

Take three ten year paths that all end up at the same compound annual rate of about twelve percent. One is perfectly smooth. One is front-loaded, with the strong years first and the weak years last. One is back-loaded, the same years in reverse.

For a lump sum of 1,00,000:

Identical. Multiplication does not care what order you do it in, so for money that goes in once, only the compound rate matters and the path is irrelevant.

For a SIP of 5,000 a month, over the same three paths:

A spread of nearly seven lakh on the same average return.

The reason is that your later instalments are much larger as a share of the total balance than your early ones. In a SIP, most of your money is only invested for the back half of the period, so what the market does late has far more of your capital exposed to it than what it does early.

Which flips a common intuition. A long run of poor returns early in a SIP is not a disaster, it is a discount, because you are accumulating units cheaply and the recovery lands on a much bigger balance. A strong early run followed by a weak finish is the genuinely damaging pattern.

The number this calculator gives you is the smooth path. Treat it as the middle of a wide distribution rather than a forecast, and run it at two or three different rates so the width of that distribution is visible.

SIP or lump sum

These are less in competition than the internet suggests, because they usually answer to different circumstances rather than different strategies.

A SIP suits money that arrives monthly. Most salaried people do not have six lakh sitting idle, they have fifty thousand a month and a decision about what share of it to invest. For them the question was never which approach is superior.

A lump sum suits money you already have. A bonus, a maturity, a sale, an inheritance.

Where the two genuinely compete is when you do have a sum and are deciding whether to deploy it at once or spread it. Two honest observations there.

Mathematically, deploying at once usually wins, because markets rise more often than they fall, so time in beats waiting. The section above is the reason: for a lump sum only the compound rate matters, and starting earlier means more of it.

Practically, the psychology is real and not a weakness. Investing a large sum the week before a sharp fall is an experience that stops people investing for years, and a strategy you abandon returns nothing. Splitting the difference, putting a portion in now and spreading the rest over the following months, gives up a little expected return in exchange for a plan you will actually stick to.

What this tool can do is price that choice. Run both modes on the same total and the same assumptions, and you can see what the caution costs. Then decide whether it is worth it to you, which is a question about temperament rather than arithmetic.

What the maturity figure is not

The number that comes back is gross. Three things stand between it and money you can spend.

Fund costs. The expense ratio is deducted from returns before they reach you, along with any platform or transaction charges. They compound against you over the same years your returns compound for you, which makes a small annual percentage a large number over twenty. The clean way to handle it is to enter your expected return already net of costs.

Tax. This is a pre-tax projection. In India what you owe on redemption depends on whether the fund is equity or debt, how long you held the units, and the rules in force at the time you sell, with an annual exemption threshold applying to long term equity gains. Those specifics change with each Union Budget, so check the current position rather than a figure you remember. Expect the amount that reaches you to be below what the tool shows.

One structural point worth knowing on a SIP. Each monthly instalment buys units on its own date, so each has its own holding period. Redeem everything at once after ten years and the units bought last month have been held for one month, not ten years, and are treated accordingly.

Inflation. Fifty lakh in twenty years does not buy what fifty lakh buys today. To see the answer in present day purchasing power, enter your expected return minus expected inflation.

This is a planning estimate rather than a promise, and nothing here is investment advice. Mutual funds carry market risk, and the value of an investment can fall as well as rise.

Questions people ask

What formula does the SIP mode use?

The standard SIP relation: monthly amount multiplied by the bracket ((1 plus i) to the power n, minus 1, divided by i), then multiplied by (1 plus i). The final factor accounts for instalments going in at the start of each month.

Why does another calculator give me a slightly different number?

Usually the start-of-month factor. Tools that treat instalments as arriving at the end of the month give a figure about one percent lower, which on ten years of five thousand a month is around 11,500.

How much did I actually invest?

The tool shows maturity value only, so work it out yourself: monthly amount times twelve times the years. On 5,000 for ten years that is 6,00,000 against a maturity value of 11,61,695.

Do both modes compound the same way?

No. SIP mode compounds monthly, so twelve percent becomes an effective 12.68 percent a year. One-time mode compounds annually. Both match standard Indian quoting practice, and it means the two modes are not quite on the same basis if you compare them directly.

Should I enter months or years?

Either. The dropdown converts for you, so sixty months and five years give the same answer.

What return should I assume?

Something drawn from the long run behaviour of the category you are buying, not its best stretch. More useful than any single figure is running two or three and treating the spread as the real answer.

Will I actually get this amount?

Almost certainly not exactly, because the projection assumes an identical return every year and markets do not work that way. For a SIP the order of good and bad years matters a great deal, and the same average return can produce outcomes several lakh apart over ten years.

Is a bad first few years fatal for a SIP?

Less than people fear, and often the opposite. Early instalments are a small share of your eventual balance, so weak early years let you accumulate cheaply while the recovery lands on a much larger amount. A strong start followed by a weak finish is the more damaging pattern.

Is the maturity figure after tax?

No. It is before tax and before fund costs. On a SIP, remember that each instalment has its own holding period, so units bought recently are not treated as long held simply because the plan is old.

References

The systematic investment relation used here is the future value of an annuity due, where each payment is made at the beginning of the period and therefore accumulates for one additional period compared with an ordinary annuity, as set out in university financial mathematics materials for the actuarial syllabus. The one-time mode uses the standard compound growth relation. The distinction between a nominal annual rate divided into periods and an effective annual rate that reflects compounding, which is what separates the two modes, follows Regulation Z and Regulation DD respectively.

1. Miguel A. Arcones, Binghamton University, Manual for SOA Exam FM, Chapter 4: Amortization and Sinking Funds. https://people.math.binghamton.edu/arcones/exam-fm/sect-4-1.pdf
2. J. Robert Buchanan, Millersville University, Loan Repayment, MATH 372 Financial Mathematics I. https://sites.millersville.edu/rbuchanan/math372/LoanRepayment-handout.pdf
3. Consumer Financial Protection Bureau (CFPB), Regulation DD, 12 CFR Part 1030, Truth in Savings, and Appendix A: Annual Percentage Yield Calculation. https://www.ecfr.gov/current/title-12/chapter-X/part-1030
4. Consumer Financial Protection Bureau (CFPB), Regulation Z, Appendix J to Part 1026: Annual Percentage Rate Computations for Closed-End Credit Transactions. https://www.consumerfinance.gov/rules-policy/regulations/1026/j/