The formula, in plain language
Future equivalent cost = Amount × (1 + rate)^years
Future purchasing power = Amount / (1 + rate)^years
Both use the same compounding idea as compound interest, just applied to rising prices instead of a growing balance.
Worked example
Suppose you have $1,000 today and inflation averages 3% per year over the next 20 years:
- Future equivalent cost: $1,000 × (1.03)^20 ≈ $1,806.11
- What $1,000 today will feel like in 20 years: about $553.68 of today's purchasing power
- Total inflation over the period: about 80.6%