Step-up SIP calculator: inputs, outputs and an example

What the step-up SIP calculator answers

A normal SIP keeps the same instalment for years. Most salaries do not stay the same, so a SIP that never rises shrinks as a share of income. A step-up SIP raises the instalment by a fixed percentage once a year. The step-up SIP calculator projects what that rising stream could grow to at a return you choose.

This post walks through the page: what each input does, what the three result cards mean, one worked example, and the assumptions behind the number. For what a step-up actually did in a real index fund over the last ten years, read how a yearly raise builds a bigger corpus. This post is about using the calculator itself.

The five inputs and their limits

The page opens with a three-way switch for Daily, Weekly or Monthly contributions. Monthly is the default. The other choices change the first field's label to "Starting daily investment" or "Starting weekly investment", and the step-up still happens once a year, not once a period.

Each slider has a small number box beside its endpoints for typing an exact value, such as 11.5% or 27 years. The amount field accepts shorthand: "50k" becomes ₹50,000 and "1.5l" becomes ₹1,50,000. The amount is also spelled out in words under the field, which makes an extra zero easy to spot.

What the results mean

Three cards update as you type:

• Invested: the total of every instalment, including the raised ones.
• Est. value: what the plan is worth at the end of the last month at your expected return.
• Est. gain: Est. value minus Invested.

Below them, a Projected growth chart plots Invested and Value at the end of each year. A donut, What makes up your corpus, splits the final value into money invested and estimated gain.

A worked example with the defaults

Leave every input at its default: ₹10,000 a month, 10 years, 12% expected return, 10% annual step-up. The calculator shows:

• Invested: ₹19.12L
• Est. value: ₹33.74L
• Est. gain: ₹14.62L

The instalment is ₹10,000 in year one, ₹11,000 in year two and about ₹23,580 in year ten.

Now open the SIP calculator and enter the same ₹10,000, 10 years and 12%. It has no step-up field, and it shows ₹12.00L invested and ₹23.23L estimated value. Setting the step-up to 0% on the step-up page gives the same answer, because both pages use the same monthly compounding.

Here is the same comparison at three step-up rates and two durations, all at 12%:

How to read the gap

The 10% step-up ends ₹10.51 lakh ahead of the flat SIP after ten years. Of that, ₹7.12 lakh is money you put in yourself and only ₹3.38 lakh is extra growth. The raised instalments arrive late, so they have little time to compound.

Over 20 years the balance shifts. The step-up plan ends about ₹98.97 lakh ahead, of which ₹44.73 lakh is extra money and ₹54.24 lakh is extra growth. A step-up is mostly a saving habit in its first decade, and the compounding shows up in the second.

The other number to check is the size of the last instalment. A 10% step-up for 20 years means an instalment of about ₹61,160 a month in year twenty. If your income will not grow that fast, a 5% step-up (about ₹25,270 in year twenty) may be closer to what you can keep up. How long it takes to build ₹1 crore shows how the step-up rate changes the years needed for a round target.

Assumptions behind the number

The calculator is arithmetic, not a forecast. It assumes:

1. One flat return every month. The annual rate is divided by 12 and applied monthly, so 12% a year works out to about 12.68% once compounded. Real funds rise and fall, and the order of good and bad years changes the result.
2. Instalments at the start of each period. Each one earns a full month (or week, or day) of return before the next arrives.
3. The step-up lands on each anniversary, by the same percentage every year.
4. No tax and no separate costs. The return you enter should already be net of the fund's expense ratio. Each instalment is a separate purchase for capital gains tax, exactly as in a flat SIP.
5. Nominal rupees. ₹1.99 crore in 20 years will buy less than ₹1.99 crore today. The inflation calculator converts it.

To test the return assumption against history instead of a guess, the MF calculator replays a SIP against a real fund's NAVs. Long-run fund returns have rarely been as smooth as a flat 12%, and why SIP returns differ from fund returns explains why.

Where it fits

Use the step-up SIP calculator to compare plans side by side: a higher start with no step-up, or a lower start with a yearly raise. If you are deciding when to begin, what a five-year delay costs puts the price of waiting in rupees. The basics of how a SIP buys units are in SIP 101, and the one-line definition is under step-up SIP in the glossary.

None of these figures is a recommendation to invest in any fund or at any amount.