How to work out the monthly investment a goal needs
Goal planning runs the SIP calculation backwards. Instead of asking what a monthly amount will grow into, it starts from the amount you need and solves for the contribution required to reach it.
Two adjustments separate a realistic plan from an optimistic one: inflating the target to what it will actually cost on the date you need it, and using a return assumption you would still be comfortable with in a bad decade.
Worked example
A target of 50,00,000 in 15 years, assuming a 12% annual return — 180 monthly instalments at a monthly rate of 0.01.
| Input | Value |
|---|
| Target amount (FV) | 50,00,000 |
| Time available | 15 years (180 months) |
| Assumed annual return | 12% |
| Monthly investment needed | 9,909 |
| Total invested | 17,83,620 |
| Growth contribution | 32,16,380 |
Cut the horizon to 10 years and the required monthly amount jumps to roughly 21,520 — more than double, for a goal only a third closer. Time is by far the cheapest input in goal planning.
How to use this calculator
- Set the target in today's money, then inflate it to the year you will need it.
- Enter the number of years available.
- Use a conservative expected return rather than a best case.
- Check the resulting monthly figure against your actual surplus.
- If it is unaffordable, extend the horizon before raising the return assumption.
Frequently asked questions
Should I inflate my goal amount?
For anything more than a few years away, yes. A goal costing 20,00,000 today will cost considerably more by the time you reach it, and planning against the un-inflated figure guarantees a shortfall.
What if the required monthly amount is unaffordable?
Extend the timeline, reduce the target, or start with what you can and step it up as income grows. Raising the assumed return to make the numbers work is the one adjustment that does not change reality.
Should short-term and long-term goals be invested the same way?
Generally not. Money needed within a few years is usually kept in lower-volatility instruments, because a market decline just before the goal date leaves no time to recover. Long-horizon goals can absorb more volatility.
How does a step-up plan change the requirement?
Committing to increase the contribution each year lowers the amount you must start with. This suits anyone whose income is expected to rise, and it front-loads less of the burden onto the present.
Should I plan each goal separately?
Usually yes. Different goals have different horizons and different tolerances for volatility, and pooling them makes it hard to tell whether any individual goal is on track.
This calculator is an educational tool. Results are estimates based on the inputs you provide and do not constitute financial advice. Verify figures with your bank, broker or a qualified advisor before acting on them.