Real Return Calculator (After Inflation)

The real return strips inflation from nominal investment returns to reveal actual purchasing power growth. The precise formula is Real Return = ((1 + Nominal Return) / (1 + Inflation Rate)) - 1, which divides rather than subtracts. Subtraction is a serviceable shortcut at low rates, so a 5% savings rate against 3% inflation gives roughly 2% real, but the approximation drifts as rates rise. At 8% nominal growth and 4% inflation the real return is (1.08/1.04) - 1 = 3.85%, not the 4% that subtraction implies.

UK inflation is measured primarily by CPI, the Consumer Prices Index, and by CPIH, which adds owner occupiers' housing costs. The Bank of England targets 2% CPI inflation. The figure actually recorded has averaged approximately 2.5-3% over the past two decades, with a spike to 11.1% in October 2022. The calculator starts at 3%, close to where CPI has run through 2026, but you can enter your own assumption, such as the Bank's 2% target, and over a long horizon that single choice moves the answer more than most people expect.

Purchasing power erosion accelerates over time. At 3% annual inflation, £100,000 buys only £74,400 worth of today's goods after 10 years, £55,400 after 20 years, and £41,200 after 30 years. Put another way, 3% inflation halves the value of money in about 24 years, 5% inflation does it in 14 years and 10% in 7. History bears the arithmetic out. £100,000 saved in 2000 had about £49,000 of purchasing power left by 2024, and £100,000 from 1980 was down to £21,000 by the same point.

Real returns differ sharply by asset class. Equities have historically delivered 4-6% after inflation, UK bonds 0-2%, and cash somewhere between -1% and +1%, frequently negative during high-inflation spells. UK property has averaged 2-3% real across 50 years, although the spread between regions is enormous. Gold has managed around 1% real over the long run. Cryptocurrencies have swung between -80% and +1,000% inside a single year with no dependable real return at all. Historic figures also carry survivorship bias, so they work better as a guide than as a forecast.

Several instruments are built to track inflation directly. UK index-linked gilts adjust both principal and interest by RPI, and after years of negative real yields they have paid a positive real return again since 2022, roughly 1% to 2% above inflation in 2026, although prices move sharply when yields change. NS&I Index-Linked Savings Certificates have been closed to new investment since 2011, leaving only existing holders able to renew. Inflation-linked annuities start 30-50% below a level annuity and then climb, which rewards a long retirement and penalises a short one. Property rents tend to rise with inflation, while capital values lag in real terms.

Retirement planning is where ignoring inflation does most damage. An income of £30k a year today needs to be £55k in 20 years at 3% inflation to fund the same life, which is why a level annuity loses ground steadily across a long retirement. Drawdown rules of thumb begin at a 4% withdrawal rate lifted by 2-3% each year, with a sustainable withdrawal rate of 3.5-4% over a 30-year retirement on UK historic data. Cash-heavy portfolios rarely keep pace with any of that. Sheltering returns in an ISA helps, since tax saved is return kept, and pension projections quoted in nominal terms should be converted to real terms before you trust them.