Inflation Adjusted Value Calculator

How this is calculated

THERE ARE TWO QUESTIONS HERE AND THEY ARE RECIPROCALS OF EACH OTHER. 'What will I need in 25 years to match $100 today?' and 'what will $100 buy in 25 years?' are the same calculation inverted - one multiplies by (1 + rate) to the power of the years, the other divides by it. People conflate them constantly, and the two answers are very different numbers: at 3% over 25 years they are $209 and $48. ⚠️ THE COMPOUNDING IS WHAT MAKES IT SURPRISING. A 3% rate sounds small and gentle, and over a single year it is. Over 25 it multiplies prices by 2.09 - and by the RULE OF 70, a standard approximation, purchasing power halves in about 70 divided by the rate in years. At 3% that is roughly 23 years, comfortably inside a working life, with nothing dramatic happening at any point. THE RATE IS AN INPUT AND SHOULD BE. Inflation is not one number: it varies by year, by country and by what you personally buy. A headline index describes a basket that may look nothing like your spending, and anyone whose costs are dominated by rent, energy or childcare can experience something quite different from the published figure. Use a rate that reflects the question you are asking, and run it twice at different rates rather than trusting one. ⚠️ AND A SINGLE AVERAGE RATE OVER A LONG PERIOD IS A SIMPLIFICATION. Real inflation arrives unevenly - quiet decades and sharp years - and the arithmetic here smooths all of that into one line. That is fine for understanding the SHAPE of the problem and poor for predicting any particular year. The further out you project, the more the result should be read as an order of magnitude rather than a figure. THE RULE OF 70 IS AN APPROXIMATION, NOT THE EXACT ANSWER. The precise halving time at 3% is about 23.4 years against the rule's 23.3, and it stays close across the range people actually use. It earns its place by being something you can do in your head, which the exact version is not. WHAT THIS DOES NOT DO IS TELL YOU WHAT TO DO ABOUT IT. Money held in cash loses purchasing power at roughly this rate; money invested may gain or lose considerably more. Comparing those is an investment question with risk attached, and it is not one a calculator should answer. GENERAL INFORMATION, NOT FINANCIAL ADVICE. For decisions about savings, pensions or investments, talk to a qualified adviser.

Common questions

Why are there two different answers?

Because there are two different questions, and they are reciprocals. 'What will I need in 25 years to match $100 today?' multiplies by inflation and gives $209. 'What will $100 buy in 25 years?' divides by it and gives $48. Both describe the same erosion from opposite ends, and people conflate them constantly — usually by taking the smaller number as the answer to the first question, which badly understates what a future goal costs. The tool shows both because knowing which one you asked is most of the work.

Is 3% really that damaging?

Over one year, no — that is exactly why it is easy to ignore. On $100 the first year costs under $3. But it compounds, and over 25 years it multiplies prices by 2.09 while cutting purchasing power by 52%. By the rule of 70, purchasing power halves in roughly 70 divided by the rate in years, which at 3% is about 23 — comfortably inside a working life, with nothing dramatic happening at any point along the way. That gradualness is the whole difficulty: no single year is alarming enough to act on.

What is the rule of 70?

A mental shortcut: divide 70 by the rate and you get roughly how many years until prices double, or equivalently until purchasing power halves. Those are the same event described from two ends. It is an approximation rather than the exact answer — at 3% the precise figure is about 23.4 years against the rule's 23.3 — and it stays close across the range people actually use. It earns its place by being something you can do in your head, which the exact calculation is not. The tool includes a self-check: what the amount buys after one halving period should come out near half, and it does.

What rate should I use?

One that reflects the question you are asking, and it is worth running the tool more than once. Inflation is not a single number — it varies by year, by country, and by what you personally buy. A headline index describes a basket that may look nothing like your spending, and anyone whose costs are dominated by rent, energy or childcare can experience something well away from the published figure. Using two or three plausible rates and looking at the spread tells you more than any single result, because the honest output for a long projection is a range.

How reliable is this over a long period?

Reliable about the shape, unreliable about the number. Real inflation arrives unevenly — quiet decades and sharp years — and applying one average rate smooths all of that into a straight line. That is genuinely useful for understanding how compounding behaves and poor for predicting any particular future year. The further out you project, the more the answer should be read as an order of magnitude. Nobody knows the average rate for the next 25 years, and a calculator that presents one to the cent is being more confident than the world allows.

Does this tell me what to do about it?

No, deliberately. Money held in cash loses purchasing power at roughly the rate shown here. Money invested may gain more, or lose more, and comparing the two is an investment question with risk attached — which is not something a calculator should answer, because the right answer depends on your timeframe, your circumstances and how much loss you could actually absorb. What this does is size the problem honestly, which is the input to that decision rather than the decision itself.

Can I use it to look backwards?

Yes — dividing rather than multiplying gives what an amount would have bought in the past, which is the same reciprocal read the other way. It is a good way to make historic figures meaningful: a salary or a price from decades ago means very little until you convert it. One caution: for actual historical periods you are better off using published index figures for those specific years than a single assumed average, because the real path was uneven and the tool's smooth line will differ from what actually happened.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Inflation Adjusted Value Calculator at https://www.bfcbrilliance.com/tools/inflation-adjusted-value-calculator.

What I entered:
- Amount today ($): ___
- Years to look ahead or back (years): ___
- Average inflation rate (%): ___

What it calculated:
- What you would need then to match it: ___
- What that amount will actually buy: ___
- Purchasing power lost: ___
- Prices multiply by: ___
- Years to halve purchasing power: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

Keep this general and do not give financial advice — flag where I should talk to a qualified adviser.

More saving & investing tools