The two formulas that matter
Future value: FV = P × (1 + r)ᵗ
Real value: RV = FV ÷ (1 + inflation)ᵗ
Real value: RV = FV ÷ (1 + inflation)ᵗ
Most calculators stop at the first formula and show you an exciting big number. The second one tells the truth: at 6% inflation, prices double roughly every 12 years, so ₹31 lakh two decades from now is not today's ₹31 lakh. Planning with real values keeps retirement and education goals honest.
Rule of 72
Divide 72 by your return rate to estimate doubling time: at 12%, money doubles every ~6 years; at 7% (FD), every ~10.3 years; inflation at 6% halves purchasing power every ~12 years.