How Much Should You Invest Monthly?
Generic advice says "invest 20% of income." That ignores your EMIs, rent, age, and goals. Here's a practical formula that works for Indian salaries from ₹5L to ₹50L CTC.
| Annual CTC | Monthly In-Hand (approx) | Minimum SIP (20%) | Ideal SIP (30%) |
|---|---|---|---|
| ₹6L | ₹42,000 | ₹8,400 | ₹12,600 |
| ₹10L | ₹65,000 | ₹13,000 | ₹19,500 |
| ₹15L | ₹90,000 | ₹18,000 | ₹27,000 |
| ₹25L | ₹1,40,000 | ₹28,000 | ₹42,000 |
| ₹50L | ₹2,60,000 | ₹52,000 | ₹78,000 |
The Formula: Age-Adjusted Investment Rate
A simple, effective rule: invest (100 minus your age) percent of your post-tax, post-EMI income. At 25, invest 75% of disposable income. At 35, invest 65%. At 45, invest 55%. This naturally reduces risk exposure as you age while maximizing compounding when you're young.
Too aggressive? Here's the minimum viable version: invest at least "your age" percent of gross salary. At 25, invest 25% of gross. At 30, invest 30%. This is the bare minimum for a comfortable retirement without depending on anyone.
Step 1: Calculate Your Investable Surplus
Take-home salary minus these non-negotiables:
- Rent / EMI — housing cost (should be ≤ 30% of take-home)
- Essential living expenses — food, transport, utilities, insurance premiums
- Emergency fund contribution — until you have 6 months' expenses saved
- Loan EMIs — car, personal, education (avoid high-interest debt)
Whatever remains after these four is your investable surplus. Invest at least 70% of this surplus — the rest can be discretionary spending (travel, gadgets, eating out).
Step 2: Allocate Across Instruments
Once you know your monthly investment amount, split it:
- EPF — automatic (12% of basic, deducted by employer). Don't opt out.
- Equity SIP — 60-70% of remaining investment amount. Choose 2-3 diversified funds (large-cap index + flexi-cap + mid-cap).
- PPF — ₹12,500/month (₹1.5L/year cap). Tax-free compounding for 15+ years.
- NPS — ₹4,167/month (₹50K/year). Extra tax deduction + equity exposure.
Step 3: Increase Every Year (Step-Up SIP)
A flat ₹10K SIP for 20 years at 12% = ₹99.9L. But a ₹10K SIP with 10% annual step-up = ₹1.90 Crore — nearly double. The step-up is not optional; it's the difference between "comfortable" and "wealthy" retirement.
Rule of thumb: increase SIP by 50% of your salary hike percentage. If you get a 15% hike, step up SIP by 7-8%. This keeps lifestyle inflation in check while supercharging compounding.
Common Mistakes
- Waiting for the "right time" — Time in market > timing the market. Every month you delay costs you future compounding.
- Investing lump sum once a year — Monthly SIP averages out volatility. Don't save all year and invest in March for "tax saving."
- Stopping SIP in market crashes — This is exactly when your SIP buys more units cheaper. Stopping during dips is the #1 wealth destroyer.
- Over-allocating to FD — Beyond emergency fund, FD barely beats inflation. Every rupee in FD beyond 6 months' expenses is an opportunity cost.
- Ignoring step-up — Same SIP for 10 years while salary doubles = under-investing your potential.
The Minimum Viable Investment Plan
If everything above feels overwhelming, start here:
- Open one SIP in Nifty 50 index fund — start with ₹5,000/month
- Open PPF account — deposit ₹500/month (minimum to keep active)
- Set calendar reminder: increase SIP by ₹1,000 every January
- Don't touch it for 10 years
Even this minimal plan gives you ₹12-15L in 10 years. Not life-changing, but infinitely better than ₹0 invested.