What Is a Monthly Investment Calculator?
A monthly investment calculator works backward from a target amount to tell you the fixed monthly SIP needed to reach it, given a tenure and an assumed rate of return.
A traditional SIP calculator asks "how much will my monthly investment grow into?" This tool asks the reverse question: "how much do I need to invest every month to reach my target corpus?" Both use the same underlying compounding math, just solved for a different variable.
Required SIP Formula: How It Is Calculated
The calculator starts from the standard SIP future value formula and rearranges it to solve for the monthly instalment (P) instead of the maturity value (M).
| Variable | Meaning |
|---|---|
| P | Required monthly investment (what this calculator solves for) |
| M | Target corpus you want to reach |
| n | Number of monthly instalments (years × 12) |
| i | Monthly rate, the annual rate divided by 12 and by 100 |
Worked example: to reach a ₹1 crore goal in 10 years assuming a 12% annual return, solving this formula gives a required monthly SIP of approximately ₹43,041, with no existing savings and no step-up.
Monthly Investment Required for Common Goals
Assuming a 12% expected annual return over 10 years, with no existing savings and no step-up:
| Goal Amount | Required Monthly SIP |
|---|---|
| ₹10 Lakh | ~₹4,304 |
| ₹25 Lakh | ~₹10,760 |
| ₹50 Lakh | ~₹21,520 |
| ₹1 Crore | ~₹43,041 |
| ₹2 Crore | ~₹86,082 |
| ₹5 Crore | ~₹2,15,206 |
How Sensitive Is the Required SIP to Your Return Assumption?
The assumed rate of return has a large effect on the required monthly SIP, since a higher return means each rupee invested does more compounding work over the same tenure. For a ₹1 crore goal over 10 years, with no existing savings:
| Assumed Annual Return | Required Monthly SIP |
|---|---|
| 8% (conservative, debt-leaning) | ~₹54,299 |
| 12% (balanced equity assumption) | ~₹43,041 |
| 15% (aggressive equity assumption) | ~₹35,886 |
A higher assumed return lowers the required SIP on paper, but assuming a rate you cannot realistically sustain is the most common way this kind of calculation goes wrong. Use the SIP Calculator to sanity-check a rate against a fund's own real historical returns before committing to it.
How Investment Duration Impacts Contributions
Delaying your investment journey increases the monthly burden non-linearly, not just proportionally. As shown in the "Cost of Delay" card above, missing just one year of early compounding forces a meaningfully larger monthly contribution later, since the money that would have been invested and compounding is simply gone from the timeline. Starting early lets the market fund a larger share of the goal instead of your salary.
Step-Up SIP and Inflation-Adjusted Goals
The Step-Up option increases your monthly instalment by a fixed percentage every year, typically matching expected salary growth, which lowers the starting SIP amount compared to a flat contribution for the same goal. The Inflation Adjustment toggle instead scales up the target corpus itself, so a ₹1 crore goal 15 years from now is treated as needing to be worth ₹1 crore in today's purchasing power, not ₹1 crore in nominal, inflation-eroded rupees. Run the target through the Inflation Calculator first if you are unsure what inflation rate to assume.
Limitations of This Calculator
Assumes a constant return rate: real markets do not deliver the same return every year. The final corpus from an actual SIP will differ from this projection based on the sequence of returns, not just the average.
Ignores tax on gains: the target corpus shown is pre-tax. Equity mutual fund gains are taxed on redemption, which reduces the amount actually available to spend.
Step-up assumes uninterrupted increases: a career break, job loss, or pay cut would mean the step-up percentage is not actually sustained every year as modelled.
How to Use This Monthly Investment Calculator
- Enter your target corpus: the amount you want to have by the end of the tenure.
- Set the tenure and expected return: how many years you have and the annual return you are assuming.
- Add any existing savings: a lumpsum you already have reduces the monthly SIP needed.
- Turn on step-up or inflation adjustment if relevant: and read the required monthly SIP in the result panel.
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Frequently Asked Questions
Disclaimer: This calculator solves for the monthly SIP required to reach a target corpus, assuming a constant annual return sustained every year of the tenure. Actual investment returns fluctuate year to year and are not guaranteed. Figures shown are pre-tax and do not account for fund expense ratios. This calculator is for educational and planning purposes only and does not constitute financial advice. Consult a SEBI-registered investment adviser before making investment decisions.