Inflation Calculator

How to Use the Inflation Calculator

Inflation is easiest to understand from two directions at once, which is why this calculator shows both. One figure is what something costs later; the other is what your money will buy later. They are the same effect seen from opposite ends.

1. Enter an amount in today's money. A salary, a savings balance, the price of something you are planning for — anything you want to project forward.
2. Set an inflation rate. Long-run averages in developed economies have generally sat between 2% and 4%, but short periods can be far higher. If you are planning conservatively, use a rate above your central bank's target.
3. Choose how far ahead. Fifteen years is a useful default because it is long enough for compounding to bite and short enough to still feel real.
4. Read both figures. The headline is what your amount will cost in future money. The first tile is what that same amount will buy — the mirror image.

The last tile is the one people remember: at your chosen rate, how many years until money loses half its value. At 3.2% it is 22 years, which is well inside a working life.

Inflation Formula

Inflation compounds exactly like interest, which is why the same exponent appears.

Note that the two results are not symmetric. A 60.4% rise in prices corresponds to a 37.7% fall in buying power, not a 60.4% fall — because the second is calculated against a larger base. Halving the value of money requires prices to double, a 100% rise.

Example

$50,000 at 3.2% inflation over 15 years

1. Growth factor: 1.032¹⁵ = 1.603967.
2. Future cost: 50,000 × 1.603967 = $80,198.36. That is what you would need then to buy what $50,000 buys today.
3. Buying power: 50,000 ÷ 1.603967 = $31,172.71. That is what $50,000, left under a mattress, would buy in fifteen years.
4. Buying power lost: 50,000 − 31,172.71 = $18,827.29, or 37.7% of the original.
5. Total inflation: (1.603967 − 1) × 100 = 60.40%.

How the rate changes the picture

Stretch 3.2% out to thirty years and the multiplier is 2.573 — prices more than double, and $100 buys $38.87 of what it buys today. That thirty-year figure is the one that matters for anybody planning a retirement.

Turning a Return Into a Real Return

The single most useful thing this calculator does is convert a return into a real return. A savings account paying 4% while inflation runs at 3.2% is not making you 4% richer; it is making you about 0.8% richer.

The precise formula is (1 + nominal) ÷ (1 + inflation) − 1 rather than simple subtraction, which is why the middle column and the third do not line up exactly. Subtraction is close enough for planning at ordinary rates and drifts once inflation goes into double digits.

The second useful application is salary. A 3% pay rise in a 3.2% inflation year is a small pay cut. Over a decade, a career of 2% rises against 3% inflation costs about 9% of real income — which is a large number that never appears on a payslip.

The third application is the one people notice last: cash. Money held in a current account paying nothing is not stable, it is shrinking at exactly the inflation rate. At 3.2%, a $20,000 buffer left untouched for five years buys about $17,086 of what it buys today — a loss of nearly $2,914 that shows up on no statement anywhere. Keeping an emergency fund in cash is still the right decision, because its job is to be available rather than to grow, but it is worth knowing what that availability costs.

Three Limits Worth Holding in Mind

Three limits worth holding in mind.

Inflation is an average, and you are not average. The headline index weights a basket of goods that may look nothing like your spending. If most of your budget is rent, childcare and energy, your personal inflation rate can run several points above the published one for years at a time.

A constant rate is a modelling convenience. Real inflation moves in bursts. A decade at 2% followed by two years at 8% produces a very different outcome from twelve steady years at 3%, even if the average matches — because the compounding happens on different bases.

Deflation is not the friendly opposite. Entering a negative rate is not supported here, and in practice falling prices tend to arrive with falling wages and rising unemployment. The arithmetic reverses; the economics does not.

Two habits follow. Run long-range plans in today's money by using a real rate — nominal minus inflation — so the answer means something you can picture. And when someone quotes a future figure, ask whether it is in today's money or theirs. The retirement calculator does this conversion explicitly, and the present value calculator handles the general case of discounting a future sum back to now.

One last practical note on comparing prices across time. If you want to know whether something is genuinely more expensive than it used to be, divide both prices by an income figure from the same year rather than adjusting one of them by an index. Prices measured in hours worked cut through arguments about which basket the index used, and they tend to match how the change actually felt at the time.

And if you are wondering why negative rates are not accepted here: sustained deflation is rare, and it behaves differently from inflation running in reverse. Falling prices usually arrive alongside falling wages and rising unemployment, so a simple compounding model would be misleading rather than merely wrong.