Crunch Inflation Calculator
Inflation is compound interest running against you. Enter any amount, a rate and a span of years, and see both directions at once: what today’s price becomes, and what a future sum shrinks to in today’s money.
How it works
Both directions are one formula: future value = amount × (1 + rate)years, and today’s-money value = amount ÷ (1 + rate)years. The purchasing-power line is the quiet one: at 3% inflation, money halves in buying power about every 24 years — the mirror image of the rule of 72.
Formula & worked example
Formula: Future value = amount × (1 + rate)^years; today’s-money value = amount ÷ (1 + rate)^years — one formula read in both directions. Purchasing power halves every ln(2) ÷ ln(1 + rate) years — about 23.4 years at 3%.
Worked example: At 3% inflation for 10 years, a $100 price becomes $134.39 — and $100 received in ten years buys only what $74.41 buys today, a 25.6% loss of purchasing power without a single dollar leaving the account.
Frequently asked questions
What does $100 become after 10 years at 3% inflation?
A price of $134.39 — and the flip side matters more: $100 received in ten years buys only what $74.41 buys today. Same formula, two directions, one uncomfortable lesson.
How long until money loses half its value?
Divide 72 by the inflation rate: at 3%, about 24 years; at 5%, about 14 years; at 7%, about a decade. Cash under the mattress is on a clock.
What inflation rate should I plan with?
Long-run US CPI averages near 3%, and most retirement planning uses 2.5–3.5%. Run your plan at 4% too — if it only works at exactly 2%, it does not work.
Is a 5% CD yield a 5% return?
Nominally yes, really no: subtract inflation. At 5% APY and 3% inflation your purchasing power grows about 2% a year — the CD Calculator shows the nominal figure, this tool shows what it will buy.
💿 Earning interest against it?
The CD Calculator works out exactly what a deposit grows to — then bring that number back here to see what it will buy.