Inflation Calculator

What This Calculator Really Does

Inflation shrinks what a fixed amount of money can buy. This tool converts a present amount into its future equivalent at a chosen average inflation rate — or works backwards, telling you what a past amount would be worth today. It uses the standard compound formula, the same one central banks and economists apply to price indices.

The number it produces is not a prediction; it is arithmetic on an assumption. You choose the rate (historical long-run averages in developed economies have hovered in the low single digits), and the tool shows the compounding consequence of that rate over your time horizon.

Everything runs locally in your browser. No amounts, no tracking, nothing uploaded — and the page keeps working offline after the first visit.

The Formula, Explained Plainly

Future buying power: Real value = Present amount ÷ (1 + r)ⁿ

• r — the average annual inflation rate as a decimal (3% → 0.03).
• n — the number of years.

Restating a past amount in today's money: multiply instead — Past × (1 + r)ⁿ. The divide-versus-multiply distinction is the whole game: inflation compounds like interest, but it works against the holder of cash.

How to Use It — In Order

1. Enter the amount — the money whose buying power you want to trace.
2. Enter the inflation rate — your assumption; official consumer-price statistics are the usual anchor.
3. Enter the years — the horizon over which the rate compounds.
4. Read the adjusted value — what the amount is worth at the other end.
5. Try a second rate — the gap between 3% and 5% over 20 years is dramatic; sensitivity matters.
6. Compare with your savings rate — money grows only if its return beats the rate you entered.

Worked Example, Verified by Hand

$100 held for 10 years at 3% average inflation:

1. 1.03¹⁰ = 1.34392 (multiply 1.03 by itself ten times).
2. 100 ÷ 1.34392 = $74.41 in today's buying power.
3. Purchasing power lost: 100 − 74.41 = $25.59, about a quarter.

At 5% instead: 1.05¹⁰ = 1.62889, so 100 ÷ 1.62889 = $61.39. Two extra points of inflation cost you 13 more cents on every dollar per decade — which is why long horizons demand real-return thinking.

Common Mistakes to Avoid

• Subtracting instead of dividing — 100 − (3% × 10) = $70 is flat-rate thinking; compounding gives $74.41, not $70.
• Entering the rate as a decimal when the field expects a percentage (0.03 vs 3).
• Using the nominal return of an investment without subtracting inflation — the real return is what grows your purchasing power.
• Assuming one year's official rate persists for decades — averages smooth spikes, but long horizons deserve a range of scenarios.
• Confusing CPI variants — headline, core and personal inflation rates can differ meaningfully.

Limitations

• A single average rate hides year-to-year variation; real inflation is lumpy.
• Personal inflation depends on your basket — rent, healthcare and education often rise faster than headline CPI.
• Not a forecast: the output is arithmetic on the rate you assume, not a prediction of it.

Expected Accuracy

The compound computation is exact at full floating-point precision and rounded only for display. Given the same rate and horizon, it matches a hand calculation to the cent.

Privacy — Your Data Never Leaves This Device

All math is local: no amounts, no horizon, no tracking — nothing is sent anywhere, and the tool works offline.

Related Tools & Guides

Natural next steps from Inflation:

• All Finance Calculators
• Compound Interest Calculator — the growth-side twin
• Inflation-Adjusted Return Calculator — real returns after inflation
• Retirement Calculator — long-horizon planning needs both
• Guide: How Inflation Is Calculated

Sources & Standards

The compounding convention matches standard price-index practice.

• U.S. Bureau of Labor Statistics — CPI (official methodology)
• IMF — international inflation statistics

Bottom Line

Inflation compounds quietly: at 3%, money loses about a quarter of its buying power in a decade. Run your own rate and horizon, then judge every investment by its real return.

Frequently Asked Questions