Inflation Calculator
What is $X today worth in N years at i% inflation? (and vice versa)
Overview
The Inflation Calculator answers two questions: what is X dollars today worth in N years at i% inflation, and conversely, what is a future amount worth in today's money? Pop in a starting figure and an annual inflation rate and you get the eroded (or inflated) equivalent.
It is built for retirement planners projecting purchasing power, contractors writing escalation clauses into proposals and journalists comparing historical prices to today's dollars. Inflation compounds, so multi-decade horizons surprise people fast.
How it works
The forward calculation is FV = PV * (1 + i)^N where i is the annual inflation rate as a decimal and N is the number of years. To find purchasing power in today's terms, divide instead: PV = FV / (1 + i)^N.
The same formula works in either direction. With a known current price and a known future price you can solve for the implied annualised rate: i = (FV / PV)^(1 / N) - 1. The calculator switches modes automatically depending on which fields you fill in.
Examples
$100 today, 3% inflation, 10 years → $134.39 future
$1,000 today, 5% inflation, 30 years → $4,321.94 future
$50,000 in 20 years at 2.5% inflation → $30,514 in today's dollars
$10 in 1990, $25 in 2020 (30 years) → ≈ 3.10% annualised
FAQ
Should I use historical or projected inflation rates?
For past comparisons, use the published CPI. For future projections, the long-run US average is around 2-3% but real rates can swing far higher or lower.
Does it handle deflation?
Yes — enter a negative rate. The result will be larger than the input in today's terms.
What about compounding monthly?
Inflation is conventionally quoted as an annual rate with annual compounding. Switching to monthly compounding has negligible effect for typical rates.
Why doesn't this match my country's official figure?
National inflation calculators use a CPI basket that may differ from the constant rate you're entering. The simple compound formula assumes a single average rate.
Is the inflation rate the same as a discount rate?
For nominal-to-real conversions, yes. For investment net present value, the discount rate should reflect your opportunity cost, which usually exceeds pure inflation.