How is inflation calculated?

Adjusted value = original × (CPI_target / CPI_origin). The CPI series captures the average price change of a representative basket of goods and services.

What's the difference between CPI and HICP?

CPI is the headline inflation measure used in the UK and US. HICP (Harmonised Index of Consumer Prices) is the EU-wide methodology used by the ECB. They differ slightly in housing-cost treatment but track each other closely.

Are these the official figures?

The calculator uses annual averages from ONS (UK), BLS (US) and Eurostat (EU). They are updated periodically and may lag the latest monthly print by a few weeks.

📈 Inflation Calculator

Compare the buying power of money across different years using official CPI series.

Economy / index

Amount

From year

To year

ℹ️ Source. UK figures from ONS CPI annual averages, US from BLS CPI-U, EU from Eurostat HICP. The calculator uses annual averages — actual monthly readings vary.

About the Inflation Calculator

The Inflation Calculator answers the classic question: what is £100 in 1990 worth today? It uses official CPI annual averages from ONS, BLS and Eurostat to give a like-for-like comparison of buying power across years.

The formula

Adjusted = Original × (CPI_to / CPI_from)

Cumulative inflation = (CPI_to / CPI_from) − 1. Annualised rate = (ratio)^1/years − 1.

Frequently Asked Questions

Why does inflation vary by economy? Each economy has its own basket of goods, exchange-rate exposure and energy mix. Currency-strong, low-import economies (Japan, Switzerland) typically have lower historical inflation than emerging-market economies.

Is CPI the same as the cost of living? Roughly, yes — CPI is the most-used proxy. RPI (UK) and chained CPI (US) are alternative measures with slightly different methodologies.

How often are figures updated? CPI is published monthly. The annual averages used here are typically finalised in January for the prior year.

⚠️

Important Note: Indices are macro averages. Personal inflation (depending on housing, transport and lifestyle mix) can be materially higher or lower.

Related Calculators

Compound Interest — See how savings grow with daily/monthly compounding.
Retirement Goal Tracker — Are you on track? Projected pot vs. pot needed for your target income.
Pension Pot Calculator — UK pension or US 401k retirement-pot projection with employer match and tax relief.