Retirement Calculator Formula & How It Works
- 4% rule: withdraw 4% of portfolio in year 1, adjust for inflation annually
- Annual expenses in retirement = current expenses × retirement spending ratio
- Savings target = Annual retirement income needed ÷ 0.04
- Monthly savings needed = solve FV formula for PMT
The 4% rule (Trinity Study) suggests withdrawing 4% of your portfolio annually — historically sustainable for 30+ years. If you need ₹60,000/month in retirement (₹7.2L/year), you need ₹1.8 crore (7.2L ÷ 0.04). Calculate how much to save monthly to reach this target by your retirement date using the FV formula.