How inflation changes your FIRE number
₹1 crore today and ₹1 crore in twenty years do not represent the same purchasing power when prices rise. Keep the date of every number clear in your retirement plan.
The expense inflation formula
Future monthly expenses = today’s monthly expenses × (1 + annual inflation rate)years to retirement. The rate must be entered as a decimal in the equation: 6% becomes 0.06. This planner assumes the same rate every year; actual inflation varies.
A ₹50,000 monthly-expense example
| Years from today | Monthly expenses | FIRE target at 3.5% |
|---|---|---|
| Today | ₹50,000 | ₹1.71 crore |
| 10 years | ₹89,542 | ₹3.07 crore |
| 20 years | ₹1,60,357 | ₹5.50 crore |
The withdrawal assumption stays unchanged in this table. The increase in the corpus comes entirely from the expense inflation assumption. These are mathematical illustrations, not inflation forecasts or sustainable-withdrawal recommendations.
Nominal returns versus real returns
A nominal return describes growth in the number of rupees. A real return describes growth in purchasing power. For an annual illustration, the relationship is real return = (1 + nominal return) ÷ (1 + inflation) − 1. Simply subtracting the rates is only an approximation.
Our FIRE calculator uses a nominal annual investment rate divided by 12 for monthly compounding. It separately increases the expense-based target with annual inflation. Enter the nominal rate in the investment field; do not first subtract inflation and then also inflate the target, because that mixes two different calculation conventions.
Why the target moves while you save
The chart compares the projected portfolio against an inflation-linked FIRE target at each age. Even if the portfolio is growing, the funding gap may grow if the target grows faster. The estimated FI age is the first month in which the projected portfolio meets that moving target, checked up to age 100.
Contributions continue in that estimate until FI is reached, including any annual step-up you selected. It does not mean that investing stops at your desired retirement age if the target has not been reached. The target-age result and estimated FI age answer different questions.
Test an expense assumption you can explain
Your household’s spending mix may differ from a broad inflation measure. Education, health costs, rent and travel do not necessarily rise at the same rate. Rather than labelling one assumption correct, compare a few values and note which expenses they are meant to represent.
Try the FIRE calculator India with the same expenses and several inflation assumptions. Then compare required investment, projected funding and the FI age. Read how to calculate a retirement corpus and the methodology before interpreting a target as a retirement decision.