If I'm 45 and want ₹20 Cr by 50, what's the required monthly SIP at 10% expected return? Show the maths.

That's an ambitious 5-year goal. Let me work through it.

The calculation

Given:
- Current age: 45
- Goal age: 50
- Goal amount: ₹20 crore
- Time horizon: 5 years
- Expected return: 10% p.a.

The Future Value of SIP formula:

$$\text{FV} = \text{Monthly SIP} \times \left[ \frac{(1 + r)^n - 1}{r} \right]$$

Where:
- $r$ = monthly return = 10% ÷ 12 ≈ 0.833% or 0.00833
- $n$ = number of months = 5 × 12 = 60 months

Solving for Monthly SIP:

$$\text{Monthly SIP} = \frac{\text{FV}}{\left[ \frac{(1.00833)^{60} - 1}{0.00833} \right]}$$

$$\text{Monthly SIP} = \frac{20,00,00,000}{\left[ \frac{1.645 - 1}{0.00833} \right]}$$

$$\text{Monthly SIP} = \frac{20,00,00,000}{77.43} ≈ ₹25.83 \text{ lakhs per month}$$

What this means

You need ₹25.83 lakh per month for the next 60 months to reach ₹20 crore at 10% expected returns.

That's ₹3.1 crore per year — roughly 37% of the goal itself, annually. The compounding gains over 5 years make up the difference (your ₹1.55 crore in contributions grow to ₹20 crore).

Reality check

Three points worth considering: ^[2]

1. Is this realistic? A ₹25+ lakh monthly SIP is viable only if your monthly post-tax surplus is substantially higher. If your total income is less than ₹1