How Much Should You Invest in a SIP Each Month?

Indians now put ₹30,954 crore into Systematic Investment Plans in a single month, spread across about 9.64 crore contributing accounts [1][4]. Almost every one of those started with the same question: how much should I put in?

And most people answer it the wrong way round. They look at what's left after the month's spending, round it down to a comfortable number, and set that as the SIP. It feels prudent. It is actually backwards — because a SIP amount pulled from spare cash is disconnected from the one thing that should decide it: what you are trying to end up with.

Table of contents

• The spare-cash trap
• Work backward from the goal instead
• The horizon matters more than the amount
• A rising SIP beats a big flat one
• The goal most people are really sizing for is retirement
• So where does 20% of income fit?
• Run the numbers yourself
• FAQ
• Conclusion and next steps
• Sources and citations

The spare-cash trap

Starting from spare cash has a quiet flaw: it makes your future depend on your leftover, and the leftover is the least stable number in your budget. It shrinks the month a bill lands, it never grows when your salary does, and it answers a question you never actually asked: "what can I afford to part with?" instead of "what will get me where I want to go?"

The result is a SIP that is precise about the wrong thing. ₹4,500 a month because that's what was left feels concrete, but it is an answer with no target attached. You could be wildly over-saving for a modest goal, or, far more commonly, quietly under-saving for a large one and not finding out for fifteen years.

The fix is to reverse the arrow. Decide the destination first, let that tell you the monthly number, and then check it against what you can afford, not the other way round.

Work backward from the goal instead

A goal has three parts: an amount, a deadline, and an assumed rate of return. Give a SIP calculator those and it returns the monthly investment. That is the number you want: one anchored to an outcome, not to a leftover.

Take the goal people name most often: ₹1 crore. At a modelling rate of 12% a year, a long-run assumption for Indian equity and never a promise, here is what a 20-year horizon needs:

Goal	Horizon	Rate	Monthly SIP
₹1 crore	20 years	12%	₹10,009

Round it off and the rule of thumb is clean: about ₹10,000 a month for 20 years gets you to ₹1 crore. (Precisely, ₹10,000/month compounds to ₹99,91,479 over 20 years.) That is a number you can act on. "Whatever's left over" is not.

But notice what did the work here. You didn't need a big monthly figure. You needed time. Change the deadline and the required amount moves far more violently than most people expect.

The horizon matters more than the amount

Hold the goal at ₹1 crore and the rate at 12%, and change only how many years you give it. The monthly SIP required is dominated by the horizon, not by how much you can spare:

Reach ₹1 crore in…	Monthly SIP needed	Total you contribute
10 years	₹43,040	₹51,64,800
15 years	₹19,819	₹35,67,420
20 years	₹10,009	₹24,02,160
25 years	₹5,270	₹15,81,000
30 years	₹2,833	₹10,19,880

Read the two ends of that table together. To reach ₹1 crore in ten years you must invest ₹43,040 a month; to reach the same ₹1 crore in thirty years you invest ₹2,833, about one-fifteenth as much. And the total you contribute out of your own pocket falls from ₹51.6 lakh to ₹10.2 lakh, because over thirty years compounding supplies the other ₹90 lakh instead of you.

This is why "start early" is not a motivational slogan; it is the single biggest lever on the number. Every year you delay does not nudge the required SIP up; it ratchets it, because you are asking a smaller stack of money to do the same job in less time. The most valuable input to your SIP amount is the one you can't buy back later.

A rising SIP beats a big flat one

There is a second lever, and it fixes the real weakness of the spare-cash SIP: that it never grows. Your salary rises most years. If your SIP doesn't, an amount that felt significant at 28 is trivial by 38, and inflation has quietly eaten its ambition.

A step-up SIP (also called a top-up SIP) solves this by increasing your contribution automatically each year, typically by a fixed percentage. Most large fund houses offer it, and a 10% annual step-up is the common default because it roughly tracks typical salary increments [2]. You set it once; the increase runs on its own.

The effect is larger than it sounds. Compare two plans over 20 years at 12%:

Plan	Starting SIP	Final value
Flat, no increase	₹10,000/month	₹99,91,479
10% annual step-up	₹5,000/month	₹99,44,358

The step-up plan reaches essentially the same ₹1 crore as the flat plan, while starting at half the monthly amount. It begins at ₹5,000, an amount a younger earner can actually manage, and grows into the heavy lifting exactly as their income does. A beginner who cannot spare ₹10,000 today is not locked out of the ₹10,000-flat outcome; they can step up into it.

And if you can start at ₹10,000 and keep the step-up, the same 20 years turns ₹10,000/month into ₹1,98,88,715, nearly double the flat result. The annual increase you barely notice on a rising salary is worth roughly another crore over two decades.

The goal most people are really sizing for is retirement

The ₹1 crore examples are useful for intuition, but for most people the number that should actually set their SIP is retirement, and it is bigger than a crore, because of inflation.

Take a 30-year-old who wants to preserve today's ₹50,000-a-month lifestyle after retiring at 60. Feed that into the retirement calculator at 6% inflation, 12% returns while working and 7% after, with money needing to last to age 85:

Input	Value
Lifestyle today	₹50,000/month
The same lifestyle at age 60 (6% inflation)	₹2,87,175/month
Corpus required at 60	₹7,67,19,898
Monthly SIP to get there	₹21,734

Two things jump out. The corpus is ₹7.67 crore, not ₹1 crore, because ₹50,000 a month today becomes ₹2.87 lakh a month in thirty years, and the corpus has to fund that. And the SIP that builds it is ₹21,734 a month. That is a real, goal-anchored number. No amount of staring at your bank balance would have produced it; only working backward from the life you want does.

If ₹21,734 is out of reach today, that is exactly where the step-up comes in: start lower and let the increases carry you, rather than setting a comfortable flat number that silently falls short.

So where does 20% of income fit?

You'll often hear the 50/30/20 rule — spend 50% of take-home pay on needs, 30% on wants, and invest 20% [3]. It's a fine sanity check, and a decent floor if you have no goal in mind yet. But treat it as a floor, not the answer.

Two caveats matter in India. First, it runs on take-home pay, not your gross CTC, and in a metro where rent alone can swallow a large share of take-home pay, the "needs" slice often crowds out the 20% [3]. Second, and more important, a flat percentage is still forward-from-spare-cash thinking with a nicer label. It tells you what's reasonable to invest; it does not tell you whether that will actually fund your goals. Use it to make sure you're investing enough, then use a goal calculation to check whether "enough" is really enough. When the goal number is higher than the 20% number, the goal wins: you either stretch the contribution, extend the horizon, or adjust the target. Those are the only three honest levers.

Run the numbers yourself

Every figure above is reproducible. Start with the goal-first approach on the SIP calculator:

Monthly Investment:    10000
Expected Return Rate:  12
Time Period:           20

1. Set Monthly Investment to 10000.
2. Set Expected Return Rate (p.a) to 12.
3. Set Time Period to 20 years.
4. Read the result: Total Value ₹99,91,479, your ₹1 crore, near enough.

Now test the horizon lever: drop Time Period to 10 and watch the total collapse to about ₹23.2 lakh on the same ₹10,000, then raise the monthly amount until you're back at ₹1 crore; you'll need roughly ₹43,000. That gap between ₹10,000 and ₹43,000 for the same goal is the value of time.

For the step-up, open Show Advanced Options on the SIP calculator, set Monthly Investment to 5000 and Annual Step Up to 10, keep 12% for 20 years, and confirm you still land near ₹1 crore from half the starting amount.

Then work your actual retirement backward on the retirement calculator: enter your age, a retirement age, today's monthly expenses, and 6% inflation, and read off the monthly SIP it demands. That number, not your leftover, is what your SIP is for.

FAQ

How much should a beginner invest in a SIP?

Start with a goal and a horizon, not a fixed rupee amount. If you have no specific goal yet, investing around 20% of your take-home pay is a reasonable floor [3]. Whatever you start with, add a 10% annual step-up so the amount grows with your income rather than staying frozen [2]. A beginner starting at ₹5,000 with a step-up can reach the same 20-year corpus as someone paying a flat ₹10,000.

How do I turn a goal into a monthly SIP amount?

Decide the target and the deadline, then let a SIP calculator solve for the monthly figure. Take a ₹1 crore target at a 12% modelling return: that's roughly ₹10,000 a month over 20 years, ₹19,819 over 15 years, or ₹43,040 over 10 years. The shorter the horizon, the steeper the monthly amount, because compounding has less time to do the work.

Is it better to invest a larger amount or for a longer time?

Time, almost always. Reaching ₹1 crore in 30 years needs about ₹2,833 a month; doing it in 10 years needs ₹43,040, fifteen times more, for the identical goal. Starting earlier is the single biggest lever on the required SIP.

What is a step-up SIP and should I use one?

A step-up (or top-up) SIP raises your monthly contribution automatically each year, usually by a set percentage such as 10%, so it keeps pace with your salary [2]. For most salaried investors it's worth using: it reaches a given corpus from a lower starting point, and a ₹10,000 SIP with a 10% step-up grows to nearly double a flat ₹10,000 SIP over 20 years.

Can I change my SIP amount later?

Yes. A SIP is a standing instruction, not a lock-in: you can increase, decrease, pause, or stop it, and a step-up automates the increases for you. What matters is that the amount stays tied to a goal, so revisit it whenever your income or targets change. For how the mechanism works, see what a SIP actually is.

Conclusion and next steps

The honest answer to "how much should I invest in a SIP" is another question: to reach what, by when? Anchor the amount to a goal and a horizon, not to whatever's left at month-end. Give the goal time, because the horizon moves the required SIP far more than the amount does, and let a step-up carry the contribution upward with your salary instead of freezing it.

If you're still deciding whether to invest monthly at all or deploy a lump sum you already hold, read SIP vs lumpsum next. Otherwise, put your own goal through the SIP calculator and your retirement through the retirement calculator, and change the horizon before you change anything else. It will show you, faster than any rule of thumb, how much your SIP actually needs to be.

Sources and citations

1. "Total amount collected through SIP during May 2026 was ₹30,954 crore." Association of Mutual Funds in India (AMFI), May 2026. https://www.amfiindia.com/articles/mutual-fund — Supports the ₹30,954 crore monthly SIP inflow and ~9.64 crore contributing SIP accounts. Retrieved 19 July 2026.
2. What Is Step Up SIP? The Meaning and How It Works. Bajaj Finserv, 2026. https://www.bajajfinserv.in/investments/step-up-sip-explained — Supports that a step-up/top-up SIP raises the contribution automatically each year, that ~10% is the common increase, and that it is set to track rising income. Retrieved 19 July 2026.
3. 50/30/20 Rule of Budgeting Explained with Example. HDFC Life, 2026. https://www.hdfclife.com/savings-plans/50-30-20-rule — Supports the 20%-of-income savings guideline and that it applies to take-home pay. Retrieved 19 July 2026.
4. India's Mutual Fund Industry Holds Rs 81.58 Lakh Crore AUM in May 2026 as SIPs Cross Rs 30,000 Crore. StartupTalky, 11 June 2026. https://startuptalky.com/india-mutual-fund-aum-sip-inflows-may-2026-amfi-data/ — Dated secondary source confirming the ₹30,954 crore May 2026 SIP inflow and 9.64 crore contributing accounts, since AMFI's own page rolls forward each month. Retrieved 19 July 2026.

Return figures in this article were computed with the same formulas the Evolfin SIP and Retirement calculators use (monthly annuity-due compounding for the SIP) and are reproducible by entering the stated inputs. The 12% return and 6% inflation are modelling assumptions, not guaranteed rates, and these are steady-rate projections: real returns arrive unevenly, so treat every figure as a planning estimate rather than a forecast.