What Inflation Stole Calculator

Why Cash Slowly Disappears

10,000 held in cash for 10 years at 3% inflation has real buying power of 7,441 — 2,559 of purchasing power has evaporated. That is 25% of the original amount, invisible because the nominal figure stays at 10,000. This tool makes the silent erosion explicit.

The Rule of 72 Applied to Inflation

Inflation of 3% halves purchasing power every 24 years. Inflation of 6% halves it every 12 years. Inflation of 10% halves it every 7 years. Fixed-income planning is extremely sensitive to this rate — which is why retirement plans often model inflation-adjusted numbers rather than nominal.

What to Do With This Number

A long-term cash balance loses purchasing power that a diversified portfolio typically outpaces. An emergency fund (3-6 months expenses) is often protected from inflation erosion via high-interest savings, money market, or short-duration bonds. Amounts beyond that typically underperform their purpose in plain cash.

A worked example

Try the defaults: cash amount of 10,000, years held of 10, average inflation rate of 3. The tool returns 2,559.24. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.

What moves the number most

The result responds to Cash Amount, Years Held, and Average Inflation Rate. Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.

The formula behind this

Real value equals nominal amount divided by (1 + inflation) to the power of years. Lost purchasing power is nominal minus real. Results are estimates for illustration purposes only. Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.

Using this to recalibrate

Repeat the calculation with smaller inputs to see how much the final figure moves. That sensitivity is where the actionable insight lives — often a modest change today produces a dramatically different lifetime total.

What this doesn't capture

This is an illustration, not a prediction. The specific figure depends entirely on your inputs — change any assumption and the headline moves. The value is in the pattern it reveals, not the exact pound figure.