How it works
Future cost = today's amount × (1 + annual inflation rate)^years. Purchasing power of a fixed future amount = amount ÷ the same growth factor. These are two different questions; neither result includes an investment return.
Worked example
Worked example: £1,000 at an assumed 10% inflation for two years becomes a £1,210 cost. A fixed £1,000 in two years would buy about £826.45 of today's goods. At 0%, both remain £1,000.
Assumptions
This is a constant-rate scenario, not a historical CPI converter or forecast. Your household's prices may change differently. Negative rates model falling prices. All figures are before any tax or investment gains.