Each SIP instalment is a separate investment that compounds for however many months remain until maturity. The first instalment grows the longest; the last one barely grows at all. The annuity formula sums all of them in one step.

Because contributions are spread over time, you also get rupee-cost averaging — buying more units when prices are low and fewer when they are high.

Given: ₹5,000/month, 12% p.a. expected return, 10 years (120 instalments)

i = 12/12/100 = 0.01  ·  (1.01)¹²⁰ = 3.30039

FV = 5,000 × (3.30039 − 1)/0.01 × 1.01 ≈ ₹11,61,695

Total invested = 5,000 × 120 = ₹6,00,000 → wealth gained ≈ ₹5,61,695

• Assumes a constant return every month; actual market returns fluctuate considerably.
• Instalments are treated as invested at the start of each month, the usual SIP convention.
• Expense ratio, exit load, stamp duty and capital gains tax are not deducted.
• Results are nominal — adjust for inflation to judge real purchasing power.

What return should I assume?
Use a conservative long-term average for the fund category rather than recent peak returns.

Can I change the SIP amount later?
Yes — for a planned annual increase, use the Step-up SIP calculator instead.

Is the maturity value guaranteed?
No. Market-linked returns vary, so treat this as a planning projection.