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Inflation calculator

See how inflation changes what money is worth, in both directions. Enter a rate yourself — the calculator uses no historical or forecast data — and find what a sum today will be worth in years to come, or how much of today's purchasing power a future sum represents. Everything runs in your browser; nothing is stored or sent.

Choose the direction: what will a sum today be worth later — or how much of today’s purchasing power does a future sum represent? The inflation rate is your own assumption; the calculator uses no historical or forecast data. All defaults are example assumptions. The calculation runs in your browser; nothing is stored.

What your result means

The headline figure is the purchasing power that remains — a today amount seen in the future, or a future amount seen today. The loss, in your currency and as a percentage, is the difference from the amount you entered.

In the 'today → future' direction the calculator also gives the amount you would need later to buy the same as today. The year-by-year table shows the value fading and the loss building up.

How this calculator works

The calculator applies a constant annual rate, compounding it up or down. In the 'today → future' direction it discounts the amount over the years: the result is how much you could still buy with it later, in today's terms. It also shows the amount you would need in future to keep today's purchasing power — the same figure grown by the rate.

In the 'future → today' direction it discounts a future amount back to now, expressing it in today's purchasing power.

The constant rate is an explicit modelling assumption; your own inflation may differ, and no historical price index is built in. Internally the calculation is unrounded and only rounded to the nearest penny for display.

Formula and variables

Purchasing power later = A / (1 + p)^nToday's value of a future sum = F / (1 + p)^nNeeded later to keep today's purchasing power = A · (1 + p)^nLoss as a percentage = 1 − (1 + p)^(−n)
A
Amount today
F
Future amount
p
Annual inflation rate as a decimal (2% is 0.02)
n
Period in years

Worked examples

Example 1: what a sum today is worth in the future

Example inputs
DirectionAmount today → purchasing power in future
Amount today€20,000.00
Inflation rate (example assumption)2.5% p.a.
Period25 years
Example results
Future purchasing power€10,787.81
Purchasing-power loss€9,212.19
Loss as a percentage46.06%
Needed later for today's purchasing power€37,078.88

At 2.5% inflation, €20,000.00 in 25 years is worth only about €10,787.81 in today's money (€20,000.00 / 1.025^25) — a loss of €9,212.19, or 46.06%. To buy the same as €20,000.00 does today, you would need about €37,078.88 then (€20,000.00 × 1.025^25). The 2.5% is an example assumption.

Example 2: what a future sum is worth today

Example inputs
DirectionFuture amount → today's purchasing power
Future amount€50,000.00
Inflation rate (example assumption)3% p.a.
Period10 years
Example results
Value in today's money€37,204.70
Purchasing-power loss€12,795.30
Loss as a percentage25.59%

€50,000.00 in 10 years is worth about €37,204.70 in today's money at 3% inflation (€50,000.00 / 1.03^10). The gap of €12,795.30 — 25.59% — is the purchasing power lost over the ten years. The 3% is an example assumption.

Assumptions

  • The inflation rate stays constant over the whole period (your chosen scenario).
  • All figures are your inputs or marked example assumptions — no researched market values.
  • A general rate is assumed; your personal inflation may differ.

Limitations of this calculator

  • No inflation forecast and no historical price index (deliberately not included in version 1).
  • Real inflation varies from year to year and by the basket of goods.
  • It says nothing about investments that might offset inflation — the real return calculator covers that.

Common misconceptions

  • Treating the rate as a forecast: The rate is your assumption, not a forecast or a historical figure. Real inflation varies year to year and by what you buy.
  • Confusing the two directions: One direction discounts a today amount into the future; the other brings a future amount back to today. They answer different questions.
  • Reading a return into it: This shows the loss of purchasing power, not what an investment might earn to offset it — the real return calculator covers that.

Frequently asked questions

Which inflation rate should I enter?

Whatever fits — a long-run reference figure, or a cautious estimate of your own. The pre-filled value is an example, not a researched or forecast rate. Your personal inflation depends on what you buy.

What is the difference between the two directions?

One discounts a today amount into the future — what will it still buy? The other brings a future amount back to today — how much of today's purchasing power is it? Same maths, different questions.

Why is the amount needed later higher than today's?

Because prices rise: to buy the same amount of goods in future as today, you need a larger nominal sum. That figure is today's amount grown by the assumed rate.

Does it use real inflation data?

No. Version 1 deliberately holds no historical index and no forecast. You enter the rate yourself, so the figures stay neutral and independent of any published numbers.

Sources and further reading

Official and independent sources on this topic. The links open each website in a new tab; no content is loaded from them into this page.

Spotted an error in the calculation or the text?

If you notice something that is wrong or unclear: let us know via the contact page. We review every report.

Last reviewed: 26/07/2026 · All calculations run in your browser – inputs are not stored. ·How we check our calculators