Inflation-Proof Portfolio Calculator

Why Real Returns Matter

Nominal returns, meaning headline investment growth, do not reflect the growth in what a portfolio can buy. A 7% nominal return alongside 3% inflation leaves a real return of 3.9%, which is the actual increase in purchasing power. Over decades that distinction becomes substantial: a 500,000 portfolio at 7% nominal grows to 1,930,000 after 20 years, but only 1,070,000 measured in today's prices once 3% inflation is removed. Planning in nominal terms overstates future wealth and understates what retirement will cost.

Historical Real Return Context

Over the long run, broad equity markets have produced mid-single-digit real returns, with a global index landing near 5% a year across more than a century and some individual markets, the United States among them, running higher. Long-run real returns on government bonds have been closer to 1-2%, and on cash close to zero or below once inflation is taken out. Inflation itself has varied widely, from around 2% through long low-inflation stretches to high single digits in the worst episodes. These are long-run averages that differ by market and by period rather than forecasts, and the inflation an investor is exposed to is the rate where the money will eventually be spent, not where it is invested.

Worked Example for Retirement Planning

Portfolio 500,000. Nominal return 7%. Inflation 3%. Years 20. Annual contributions 10,000. Real annual return 3.88%. Nominal final approximately 2,345,000. Inflation factor 1.81x. Real purchasing power approximately 1,298,000. Against the opening balance that is 2.6 times in real terms and 4.7 times nominally, but 200,000 of it arrived as contributions rather than growth: measured against the 700,000 actually paid in, the real result is 1.85 times. Nominal figures overstate what a balance will buy.

What the Calculator Does Not Model

Specific asset mix returns during different inflation environments. Bond duration effects during inflation spikes. Property and commodities as inflation hedges. Inflation-linked government bonds, which adjust with a domestic price index. Specific tax effects on real returns. Sequence of returns risk. Currency effects for international holdings. The calculator uses constant rates, while real portfolios experience varying inflation and returns, creating more complex dynamics.

Inflation-Protecting Strategies

Assets behave differently when inflation runs high. Broad equity exposure has produced the highest long-run real returns of the main asset classes, though equities have often fallen during the inflation spike itself before recovering. Inflation-linked government bonds, issued by many countries under different names, adjust principal or coupon with a domestic price index and hold real value by design, at the cost of a lower return than conventional bonds when inflation turns out lower than the market had priced. Property and commodities have shown some historical association with inflation, commodities more strongly and more erratically. Holding assets in several currencies limits exposure to a single country's inflation. Long-dated conventional bonds and large cash balances have historically fared worst. This calculator prices the erosion on a static portfolio at a constant rate and does not model any of these behaviours.