Your cash position
Nominal balance vs real purchasing power
The flat line is what your statement shows. The falling line is what it's worth.
Your inflation defense plan
What inflation does to your idle cash
$20,000 sitting in cash at 3.5% average inflation buys only $14,178 worth of today's goods after 10 years - a silent loss of $5,822 (29.1% of its purchasing power).
The half-life of your money: 20.1 years
At 3.5% inflation, cash loses half its real value every 20.1 years. The account balance never changes - that's what makes this the most invisible fee in finance.
Defensive moves
• Keep your emergency fund (3–6 months of expenses) in a high-yield savings account - liquid, but at least partially offsetting inflation.
• Cash beyond the emergency buffer with a 5+ year horizon belongs in diversified investments - run the same numbers in our Compound Interest calculator to see the other side of this curve.
• Re-check any fixed sums you're 'saving up' (house deposit, car fund): a multi-year target priced in today's money will cost more when you arrive.
• This model uses a constant average rate; real inflation varies year to year, and your personal rate depends on what you actually buy.
How the inflation decay calculator works
The calculator deflates your cash by the inflation rate over time: real value equals your amount divided by (1 + inflation) raised to the years held. The account balance never changes - that's what makes inflation the most invisible cost in personal finance. What changes is what the balance buys, and the chart shows the two lines diverging: nominal flat, real falling.
The half-life figure is the most intuitive way to feel the effect: at 3.5% inflation, cash loses half its purchasing power in about 20 years; at 7%, in about 10. This doesn't mean holding cash is wrong - your emergency fund belongs in cash or near-cash - it means cash beyond your safety buffer has a real, measurable carrying cost that compounds against you exactly like interest compounds for you.
The same decay math applies to debt in reverse, which is an underappreciated silver lining: a fixed-rate loan balance is also being eroded by inflation, since you're repaying it in future dollars that buy less than the dollars you borrowed. This doesn't make debt free - interest still costs more than inflation saves on any ordinary consumer loan - but it's part of why fixed-rate, long-term debt behaves differently under high inflation than short-term or variable-rate debt.
Frequently asked questions
- How much cash should I actually hold?
- A common framework: 3-6 months of essential expenses as an emergency fund in a high-yield savings account, plus cash for known near-term expenses. Beyond that, money with a 5+ year horizon has historically done better invested - see our Compound Interest calculator for the other side of this curve.
- What inflation rate should I use?
- Central banks target around 2-3%, but recent years have seen spikes well above that. Run 3% for a baseline and 5-6% for a stress test. Your personal rate also depends on what you buy - housing, education, and healthcare have often outpaced headline inflation.
- Does a high-yield savings account beat inflation?
- Sometimes, roughly, in high-rate periods - and it always beats a 0% checking account. Even partially offsetting inflation meaningfully extends your money's half-life, which is why idle cash belongs in an interest-bearing account at minimum.
- Is this the same as 'real vs nominal' returns?
- Yes. Nominal is the number on your statement; real is what it buys. This calculator applies that adjustment to held cash - the same logic applies to any investment return you evaluate.
- Why does inflation feel higher than the official rate?
- Headline inflation is a broad basket average; your personal spending mix may lean toward categories - housing, groceries, healthcare, education - that have often risen faster than the average. Run this calculator at both the headline rate and a personal rate closer to your actual spending pattern to see the gap.