Inflation Calculator

Two questions in one calculator: What will today's money be worth in the future? and What was past money worth in today's terms? Future uses a rate you pick; historical uses UK CPI data back to 1950.

What inflation actually is

Inflation is the rate at which the general price level rises over time — equivalently, the rate at which the purchasing power of money falls. A 3% annual inflation rate means a basket of typical consumer goods that costs £100 today will cost £103 in a year, £109.27 in three years, and roughly £180.61 in twenty years. That last number usually surprises people: a steady, “low” 3% almost doubles prices over a generation.

How the future-value math works

Future nominal price = today's price × (1 + r)ⁿ, where r is the annual inflation rate (as a decimal) and n is the number of years. The inverse — what future money is worth in today's purchasing power — divides instead of multiplies:

Future = Today × (1 + r)n

Today's purchasing power = Future ÷ (1 + r)n

Worked example: a salary that “doubled”

Your salary went from £25,000 in 2005 to £55,000 in 2025. Nominally you more than doubled it. But UK CPI rose roughly 64% over that period, so £25,000 in 2005 is worth about £41,000 in 2025 money. Your real raise was £55,000 − £41,000 = £14,000, or 34% — not 120%. This is why “real” figures (inflation-adjusted) always tell a different story than “nominal” ones.

Why historical inflation matters for planning

When you set a long-term financial goal — “£500,000 by retirement” — you're using today's mental price anchors. Houses, holidays, and groceries will not stay at today's prices. To plan in real terms, either:

• Inflate your goal each year as your expenses inflate, or
• Use real (inflation-adjusted) returns in your projections — subtract your expected inflation rate from the nominal return. A 7% nominal return with 3% inflation gives a 4% real return. Use 4% when sizing your contributions.

Either approach works. The fatal mistake is mixing them — projecting nominal returns against today's prices, which makes future balances look more impressive than they are.

The big historical numbers (UK)

• £1 in 1950 ≈ £37 in 2025. About 97% of purchasing power lost over 75 years.
• £1 in 1970 ≈ £18 in 2025. The 1970s and early 1980s did most of the damage.
• £1 in 1980 ≈ £4.40 in 2025. About 77% of purchasing power lost over 45 years.
• £1 in 2000 ≈ £1.85 in 2025. The post-2008 and post-2022 inflation surges account for much of this.
• £1 in 2020 ≈ £1.30 in 2025. The cost-of-living crisis in a single decimal.

Why the 2022-23 spike was different

UK CPI peaked at 11.1% year-on-year in October 2022 — the highest in roughly 40 years. Most of it came from energy (Russian gas supply shock), food (war-driven grain prices, fertiliser, shipping), and sticky services inflation as labour markets tightened. The Bank of England raised the base rate from 0.1% to 5.25% in response. Inflation has since fallen but not all the lost purchasing power comes back — prices stayed up; only the rate of change normalised.

Inflation and investment returns

Most published investment returns are nominal — they don't subtract inflation. To know what you actually gained in purchasing power, you need the real return:

Real return ≈ Nominal return − Inflation rate

More precisely: (1 + real) = (1 + nominal) ÷ (1 + inflation), but the approximation is fine for small rates. A savings account paying 4% when inflation is 5% is losing you money in real terms, even though the nominal balance grows. This is why “safe” cash savings during high-inflation periods can be the riskiest choice of all.

What this calculator does NOT model

• Personal inflation rates. Your basket isn't the ONS basket. If you spend disproportionately on housing, energy, or childcare, your real inflation rate can differ from headline CPI by several percentage points.
• Regional variation. Inflation in London diverges from rural Scotland; Gibraltar tracks UK CPI loosely but is sensitive to fuel and import costs.
• Wage inflation. Different series, often higher than CPI in tight labour markets, lower in slack ones.
• Asset price inflation. CPI excludes most asset prices (housing, equities). The official figure can dramatically understate the “real” cost of buying into wealth.
• Pre-1989 precision. The modern CPI series began in 1989. Earlier data uses RPI as a proxy with broadly similar but not identical methodology.

Disclaimer

Educational only. Inflation calculations are inherently approximations — different price baskets, methodology revisions, and regional variation all introduce uncertainty. Use these figures for planning and intuition, not for legal, tax, or compensation calculations.