Lumpsum Calculator

One deposit, then left alone

A lumpsum investment is money you put in once and do not touch. No monthly contributions, no withdrawals, just a single amount left to compound.

This projects where it ends up. Give it the amount, a rate of return you expect, and a number of years, and it returns three things: what you put in, what it earned, and what you finish with.

The arithmetic is compound growth and it is not complicated. What is worth spending time on is the middle input, because the amount and the years are facts about your plan and the rate is a guess about the future. Almost everything that can go wrong with a projection like this goes wrong there, and there is a section on it below.

Three fields

1. Investment Amount. The single sum you are putting in.
2. Expected Rate of Return. An annual percentage. This is an assumption you are making, not a rate anybody is offering you.
3. Tenure. How many years the money stays invested. Whole years.

Press Calculate and you get the invested amount, the earning, and the future value, formatted in the Indian numbering system so a figure like nine lakh sixty four thousand reads the way you would say it out loud.

Run it more than once. A single projection looks like a prediction, and three projections at different rates look like what this actually is, which is a range.

The formula, and the one thing it assumes

Compound growth, in its plainest form:

Future value = P × (1 + r)ⁿ

P is what you put in, r is your expected annual return as a decimal, and n is the number of years. Then the earning is simply the future value minus what you put in.

The compounding here is annual. Your money grows once a year, at the rate you entered, and the result of each year becomes the base for the next.

That is the standard convention for lumpsum projections in India and it matches how a compound annual growth rate is quoted. It is worth naming because the sibling tool for systematic investments compounds monthly, and the same headline percentage produces a slightly different answer under the two conventions. Twelve percent compounded monthly works out to an effective 12.68 percent a year, which over five years is about 3 percent more money.

Neither convention is wrong. They answer to different quoting practices. What matters is knowing which one you are looking at, and this one is annual.

A lakh at twelve percent

Investment 1,00,000, expected return 12 percent, tenure 5 years.

Year by year, so you can watch it build:

• After year 1: 1,00,000 × 1.12 = 1,12,000
• After year 2: 1,12,000 × 1.12 = 1,25,440
• After year 3: 1,25,440 × 1.12 = 1,40,493
• After year 4: 1,40,493 × 1.12 = 1,57,352
• After year 5: 1,57,352 × 1.12 = 1,76,234

Future value 1,76,234, earning 76,234.

Look at the size of each year's gain. Year one adds 12,000. Year five adds 18,882. Same rate, same money, and the last year earns more than half as much again as the first, because it is growing on a larger base.

That widening is the entire point of compounding, and it is why the next section matters more than the rate does.

Time does most of the work

Same lakh, same twelve percent, three different holding periods:

Doubling the time from 10 years to 20 does not double the outcome. It triples it.

Now compare that against changing the rate instead. At ten years, moving from 8 percent to 15 percent, which is a large and optimistic jump, takes you from 2,15,892 to 4,04,556. Not quite a doubling.

Extending from 10 years to 20 at a steady 12 percent takes you from 3,10,585 to 9,64,629. More than three times.

So the years are the more powerful lever, and they are also the one you have some control over. You cannot make the market return more. You can start earlier and leave it alone longer.

How long until it doubles

A quick mental shortcut worth carrying, because it lets you sanity check any projection without a calculator.

Divide 72 by the rate to get the doubling time in years.

At 12 percent, 72 divided by 12 is 6, so your money should roughly double every six years. Check it against the table above: at 5 years the multiple is 1.76, and at 10 years it is 3.11, so it crossed 2 somewhere around year six. Correct.

How good is the shortcut? Here it is against the exact figures:

Close enough to be useful across the range people actually invest at, and it drifts a little at higher rates. Handy for a rough answer in your head, not for a plan.

The rate box is the weakest number on the page

The amount is a fact. The tenure is a decision. The rate is a guess, and the whole projection rests on it.

The trouble is that the output does not look like a guess. It comes back to the rupee, and a figure like 9,64,629 carries an air of precision that the input behind it does not deserve.

So treat the single answer as one point in a range, and get the range by running the tool three times.

That spread, from about 2.2 lakh to about 4 lakh, is the honest answer. Anyone who tells you the answer is 3,10,585 is reporting the middle of a range as though it were a fact.

Two further points about what a constant rate is hiding.

Real returns do not arrive in equal annual slices. A fund that averages 12 percent across a decade might deliver 30 percent one year and lose 15 percent the next. For a single lumpsum this matters less than you might expect, because the order in which the good and bad years arrive does not change where you finish, only the compound rate does. That is a genuine advantage of lumpsum investing over regular contributions, where the order matters a great deal.

And a rate that looks reasonable for one kind of asset is fantasy for another. Whatever number you use should come from the long run behaviour of the thing you are actually buying, not from the best year it ever had.

Three things that sit between this figure and your pocket

The future value is a gross figure. Three things stand between it and money you can spend.

Costs. Fund expense ratios, platform charges and any transaction costs come out of your return before you see it. They are usually quoted as a small annual percentage and they compound against you exactly as returns compound for you. The blunt way to handle it is to enter your expected return net of costs rather than gross.

Tax. This projection is entirely pre-tax. What you eventually owe depends on what you invested in, how long you held it, and the rules in force when you sell. In India the holding period determines the treatment, equity and debt are handled differently, and there is an annual exemption threshold on long term equity gains. Those specifics move with each Union Budget, so check the current position rather than a number you remember, and expect the post-tax figure to be meaningfully below what you see here.

Inflation. The most easily forgotten of the three. Nine lakh in twenty years does not buy what nine lakh buys today. If you want the answer in today's money, enter a real rate of return, meaning your expected return minus expected inflation, and read the result as present-day purchasing power. On a 12 percent expectation with 6 percent inflation, that means entering 6, and the twenty year figure falls from 9,64,629 to about 3,20,714. Sobering, and more honest.

This is a planning estimate, not a promise, and nothing here is investment advice.

Questions people ask

What is a lumpsum investment?

A single amount invested once and left to grow, with no further contributions. The opposite approach is investing a fixed sum every month, which the mutual fund calculator handles.

How is the future value calculated?

Amount multiplied by one plus the rate, raised to the number of years. On 1,00,000 at 12 percent for 5 years that is 1,00,000 times 1.12 to the power of 5, which is 1,76,234.

Does it compound annually or monthly?

Annually. Your money grows once a year at the rate you entered. This matches how a compound annual growth rate is quoted and is the standard convention for lumpsum projections.

What rate should I use?

Whatever is realistic for what you are actually buying, based on long run behaviour rather than a good year. More usefully, run three: a conservative figure, a central one and an optimistic one, and treat the spread as your answer.

Are the results after tax?

No, they are pre-tax and pre-cost. What you owe depends on the asset, the holding period and the rules at the time you sell, all of which change. Expect the amount that reaches you to be lower.

Does it account for inflation?

No. To see the answer in today's purchasing power, enter your expected return minus expected inflation. On 12 percent with 6 percent inflation, enter 6.

How quickly does money double?

Divide 72 by the rate. At 12 percent that is about six years, which is close to the exact figure of 6.12 years.

Is a lumpsum better than investing monthly?

They suit different situations and are not really competitors. A lumpsum needs money you already have, and its outcome depends only on the compound rate rather than on when the good and bad years arrive. Regular investing suits money that arrives monthly, and its outcome is much more sensitive to the order of returns.

References

The projection uses the standard compound growth relation, under which a present amount accumulates to a future value at a periodic rate applied over a number of periods, as set out in university financial mathematics materials for the actuarial syllabus. The convention of expressing an annual rate as a periodic rate multiplied by the number of periods in a year, and the distinction between that nominal figure and an effective annual rate that reflects compounding, follow Regulation Z and Regulation DD respectively.

1. J. Robert Buchanan, Millersville University, Loan Repayment, MATH 372 Financial Mathematics I. https://sites.millersville.edu/rbuchanan/math372/LoanRepayment-handout.pdf
2. 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
3. Consumer Financial Protection Bureau (CFPB), Regulation DD, Appendix A to Part 1030: Annual Percentage Yield Calculation. https://www.ecfr.gov/current/title-12/chapter-X/part-1030