How to get an accurate result from the SIP Calculator

A calculator is only as accurate as its inputs, and SIP inputs have four quiet traps. Get them right and the projection will be a useful comparison. Get one wrong and the answer can be off by lakhs. Here is the checklist.

Use the exact monthly amount and a realistic return

Enter the amount you will actually invest each month, not the amount you hope to invest. Then test two returns: an optimistic one and a cautious one. ₹5,000 a month at 12% a year for 10 years grows to ₹11,61,695. You invest ₹6,00,000 over those 10 years, so the gain is ₹5,61,695. At 10% instead of 12%, the same SIP grows to ₹10,32,760 — a gap of about ₹1,29,000 from a two-point return difference. That range is the honest answer.

Confirm the tenure and the timing

This calculator assumes each investment is made at the start of the month, so even the last one earns one month of growth. Some calculators assume end-of-month investments, which gives a slightly lower figure. The difference is one month of return on the final balance — small, but it explains why two calculators can disagree by a few thousand rupees.

Remember what sits outside the formula

Fund expenses, exit loads and taxes are not in the SIP formula, so the amount you actually receive can be lower than the projection. Also expect rounding differences: the calculator rounds only the display, while a fund’s statement rounds each transaction. A gap under a few thousand rupees over a long SIP is rounding and timing; a gap in lakhs is an input error.

Frequently asked questions

Why does another calculator give a different answer?

Usually the start-of-month versus end-of-month assumption, or a different return. Check both before assuming one is wrong.

Should I use the fund’s past return as the expected return?

Only as a test case. Past returns do not guarantee future returns, so always test a lower return alongside the past one.

Does the calculator handle a step-up SIP?

No. A step-up SIP, where the monthly amount rises each year, needs a separate calculation for each year’s amount.