Type an amount, an annual inflation percent, and a span of years. Same stance as stamp duty: the rate is yours — there is no country table and no live API. Formula: A × (1 + r)n.
Two directions are covered by the same underlying compound-growth formula. Forward calculates future value: FV = A × (1 + r)n, showing what a past amount would be worth today (or in the future) after compounding at your entered inflation rate over n years.
Backward calculates present value: PV = A ÷ (1 + r)n, which answers a different question — either the real buying power a past amount actually had, or what a future sticker price is worth in today's money once you discount out the inflation between now and then.
As a self-check on the maths: 1,000 growing at 3% annually for 10 years compounds to 1,343.92. Going the other way, 1,000 in 10 years' time, discounted back at 3% inflation, has a buying power of 744.09 in today's money — the same rate and time period applied in each direction, just solving for a different unknown.
Forward answers 'what will this amount be worth after inflation compounds over time' (future value). Backward answers 'what is this amount really worth once you account for inflation' (present value, or buying power) — they use the same rate and time period, just solving in opposite directions.
Compound inflation applies the rate to an amount that has already grown from previous years, so the effect accelerates over time — this is how inflation is virtually always measured and reported, rather than a flat percentage applied only to the original amount each year.
It's what a given amount of money can actually purchase once inflation has eroded its value over time — 1,000 today won't buy as much in 10 years if prices have risen at 3% annually, and the backward calculation shows exactly how much less.
Yes — enter the amount, the number of years between the two points, and your assumed inflation rate, and the calculator adjusts one figure into the other's terms so you can compare them meaningfully.
