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Plot No. 16 · Money & Finance

Inflation Calculator

See how inflation erodes the value of money over time. Enter an amount, an annual inflation rate and a number of years to find the future equivalent cost and how much your money will really be worth once prices compound.

Inputs
Results
Equivalent value in the future£1,343.92
Cumulative price increase34.4%
What today's amount will be worth£744.09
Amount today£1,000.00

Future value = amount times (1 + rate) raised to the power of the number of years. The same goods that cost the amount today will cost the future figure once inflation compounds.

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How the inflation calculation works

Inflation steadily raises prices, which means a fixed sum of money buys less over time. This calculator compounds an annual inflation rate over a number of years using the formula future value equals the amount times one plus the rate, raised to the power of the years. It then shows both the future cost of the same goods and how little today's amount would be worth in future money.

The two figures are mirror images. The equivalent future value tells you how much more you will need later to buy what the amount buys now, while the buying power figure shows the erosion in the opposite direction.

How to use the inflation calculator

  1. Enter an amount of money in today's terms.
  2. Set an annual inflation rate.
  3. Choose the number of years, then read the future equivalent value, the cumulative price rise and the future buying power.

Worked examples

1,000 at 3 percent inflation for 10 years

Inputs: Amount 1,000, rate 3 percent, 10 years.

Result: A future equivalent of about 1,343.92, a cumulative price increase of roughly 34.4 percent, and today's 1,000 worth only about 744.09 in future buying power.

A higher rate over the same period

Inputs: Amount 1,000, rate 5 percent, 10 years.

Result: The future equivalent climbs to about 1,628.89, showing how a couple of extra percentage points compounds sharply over a decade.

Limitations and common mistakes

Edge cases and limitations

  • It assumes a single constant inflation rate for the whole period, whereas real inflation varies year to year.
  • It does not account for any interest or investment return that might offset inflation on the money itself.
  • Figures are shown to two decimal places, and the result is only as realistic as the rate you choose.

Common mistakes

  • Using a one-off recent inflation spike as the long-run rate, which overstates the erosion. A long-run average of 2 to 3 percent is a more sensible planning figure.
  • Confusing the future cost with the buying power. One rises with inflation while the other falls.

Frequently asked questions

How does this inflation calculator work?

It compounds inflation year on year using the formula future value equals amount times (1 plus rate) to the power of years. At 3 percent for 10 years, 1,000 today equals about 1,344 in future prices for the same basket of goods.

What inflation rate should I use?

Central banks often target around 2 percent, while long run averages tend to sit between 2 and 3 percent. For planning you can use the official target, a recent published rate, or a slightly higher figure to be cautious.

What is the difference between future cost and buying power?

Future cost shows how much more you will need to buy the same things later. Buying power shows the opposite view, how little today's fixed amount of money will purchase after inflation has eaten into it.

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