Inflation-Adjusted Investment Return Calculator

Real Returns and Inflation Guide

What's the difference between Real and Nominal Returns?

Nominal return: the stated percentage return before inflation adjustment. Real return: the Fisher equation: (1 + real) = (1 + nominal) / (1 + inflation). Simplified: real return ≈ nominal − inflation. Example: savings account at 4.5% with 3.5% inflation: real return ≈ 1%. You are barely keeping up with inflation. £10,000 grows to £14,500 nominally but the real purchasing power increase is only about £1,000 in today's money. The real return is the only figure that tells you whether you are actually building wealth, or merely keeping pace with rising prices.

What should I know about Inflation and Cash Savings?

Cash held without investing is destroyed by inflation at the full inflation rate. £10,000 in cash at 3% inflation for 20 years: real value = £10,000 / 1.03²⁰ = £5,537. You still have £10,000 but can only buy what £5,537 would buy today. This is why saving in cash alone is a wealth-destroying strategy over long periods. The Bank of England's 2% inflation target means £1 today should be worth approximately 67p in 20 years — this is considered a healthy, stable economy. Hyperinflation (Zimbabwe 2008, Venezuela 2018) shows the extreme end of what happens when this control is lost — savings can become worthless within months.

What should I know about Long-Run Real Returns by Asset Class?

Historical real returns (UK, long-run averages after inflation): equities (UK stock market): approximately 5-7% real per year. Global equities: 5-6% real. UK residential property: 2-3% real (including rental income, excluding costs). Index-linked gilts: 0-1% real. Cash/savings accounts: 0-1% real (sometimes negative in high inflation periods). This is why long-term investors allocate heavily to equities — the equity risk premium (return above inflation) has historically been substantial. Short-term, cash tends to preserve capital better during volatile periods, but over decades-long horizons it reliably underperforms equities after inflation.

What do I need to know about Sequence of Returns Risk?

The order of returns matters for investors drawing down funds in retirement. Two investors both average 5% real return but one experiences losses early, one late. The investor suffering early losses has a much worse outcome because losses early compound the damage — there is less capital remaining to benefit from subsequent gains. This sequence of returns risk explains why a 100% equity portfolio can be dangerous in the years immediately before and after retirement. The sequence risk is also why many retirement strategies recommend holding 1-3 years of expenses in cash or bonds, so withdrawals during a market downturn don't force selling equities at a loss.

Nominal Return Tells You the Number; Real Return Tells You the Truth

A nominal return is simply the percentage your investment grew by in actual currency terms — the number on your statement. A real return strips out inflation to show how much your purchasing power actually grew, which is the figure that matters for any long-term financial goal measured in what money can buy, not what it says on paper. The approximate relationship is real return ≈ nominal return − inflation rate, though the precise (Fisher) formula divides (1 + nominal) by (1 + inflation) and subtracts 1, which matters more at higher rates of either figure. A portfolio showing an impressive 8% nominal annual return during a period of 6% inflation has, in real terms, barely grown at all — a distinction that matters enormously for retirement planning spanning decades.

Why Real Returns Matter Most for Long-Horizon Goals

Over a single year, the gap between nominal and real returns is usually a modest drag easy to shrug off. Over several decades, that gap compounds just as powerfully as the returns themselves, which is why retirement and long-term savings projections should always be modeled in real terms — otherwise a plan can look comfortably funded on paper while badly understating how much purchasing power will actually be needed decades from now, since future living costs will have risen too. This is also why cash sitting in a low-interest account can quietly lose real value every year even while the nominal balance never falls, and why inflation risk, not just market volatility, deserves a seat at the table in any long-term financial plan.

Why Different Inflation Measures (CPI vs RPI vs Personal Inflation) Give Different Real Returns

Adjusting a nominal return for inflation requires choosing which inflation measure to use, and the choice can meaningfully change the real return figure produced. The Consumer Price Index (CPI) is the UK's main official inflation measure and tends to run lower than the older Retail Price Index (RPI), partly because of methodological differences in how the two indices calculate averages and what they include, such as RPI historically including mortgage interest payments and certain housing costs that CPI excludes or treats differently. Using RPI instead of CPI to deflate the same nominal return will generally produce a lower real return figure, simply because RPI has typically shown a higher inflation rate over most periods. Neither official measure, however, necessarily reflects any individual's actual experience of rising prices, since both are built from a fixed basket of goods and services weighted to represent average national spending patterns; someone whose own spending is weighted more heavily toward categories rising faster than the basket average, such as heavier energy or housing costs relative to income, experiences a "personal inflation rate" that can differ noticeably from either published figure, meaning their true real return on savings or investments may be lower than a calculation using CPI alone would suggest.

Worked Example: Turning a Nominal Return Into a Real One

An investment returns 8% nominal in a year during which inflation runs at 3%. The quick approximation (nominal minus inflation) gives a real return of roughly 5%. The more precise Fisher equation calculates it as (1 + nominal) / (1 + inflation) − 1 = (1.08 / 1.03) − 1 ≈ 4.85% — close to the approximation at low rates, but the gap widens as either figure gets larger. Now consider a savings account paying 2% nominal interest during a year when inflation runs at 5%: the approximation suggests a real return of −3%, and the precise calculation gives (1.02 / 1.05) − 1 ≈ −2.86% — meaning the saver's money, while nominally growing, actually lost purchasing power over the year. This is the core reason "my savings account pays interest, so I'm not losing money" can be false in real terms during periods of elevated inflation, and why comparing any return figure to the inflation rate over the same period is essential before judging whether an investment genuinely grew your wealth.

Long-Run Average Nominal vs Real Returns by Asset Class

These are broad historical tendencies drawn from long-run averages across many decades, cycles, and countries — they are not predictions, guarantees, or a substitute for your own research, and any specific future period, including the next several years, can and does deviate meaningfully from long-run averages in either direction.