Real Rate of Return Calculator
Adjust a nominal return for inflation to compute the real rate of return (purchasing-power return).
Input Data
Results
At a glance:The Real Rate of Return adjusts a nominal return for inflation to show the return that truly increases purchasing power — it answers how much more you can actually buy after prices rise. It uses the Fisher equation: real rate = (1 + nominal rate) ÷ (1 + inflation rate) − 1, which is more accurate than the 'nominal − inflation' approximation. The real rate can be negative — when inflation exceeds the nominal return, purchasing power actually falls and money 'shrinks' in real terms.
Formula
Real rate = (1 + nominal rate) ÷ (1 + inflation rate) − 1 (Fisher equation).
Approximation: real rate ≈ nominal rate − inflation rate.
$$r_{real} = \\dfrac{1 + r_{nominal}}{1 + i} - 1$$$$\: r_{real} \\approx r_{nominal} - i$$How to Use
- Enter the nominal return (the stated annual return of the investment or deposit).
- Enter the expected inflation rate.
- The inflation-adjusted real rate of return shows instantly.
FAQ
Why not just subtract inflation from the nominal return?
'Nominal − inflation' is only an approximation; the accurate method is the Fisher equation (1 + nominal) ÷ (1 + inflation) − 1. When rates or inflation are high, the gap between the two becomes noticeable. The subtraction omits the cross term (inflation × real return) and slightly overstates the real return, so for precise or high-inflation situations use the Fisher equation, which is what this calculator applies.
What does a negative real return mean?
It means inflation has eroded the nominal return, so your purchasing power is actually falling. For example, a 2% deposit with 3% inflation gives a real return of about −1% — your money 'shrinks' in real terms even though the balance grows.
Why use the Fisher equation instead of 'nominal return − inflation', and how much do they differ?
The subtraction method is the most intuitive estimate and often good enough, but it is only an approximation; the exact method is the Fisher equation. The reason is that the nominal return contains both compensation for inflation and the true real growth, and inflation erodes not just the principal but also the nominal return itself — simple subtraction ignores this second-order erosion (the inflation × real-return cross term), slightly overstating the real return. The difference is tiny at low rates: nominal 6.5%, inflation 2.4% gives 4.1% by subtraction but about 4.00% by Fisher. It widens at higher rates: nominal 10%, inflation 5% gives 5% vs about 4.76%; at nominal 50%, inflation 40% the gap is 10% vs about 7.14%. Use subtraction for quick mental math in low-inflation environments; use the Fisher equation for precision, high inflation or serious planning. Pair it with our inflation calculator.
Why is the real rate of return especially important for retirement and long-term investing?
Both span decades, and inflation's erosion compounds over time — ignoring it badly overstates future purchasing power. At 3% inflation, prices roughly double in about 24 years (rule of 72), so HK$1 million today is worth about half as much then. Retirement planning should therefore be done in real terms: if your nominal return is 7% and inflation 3%, plan with the real return of about 3.88% so all figures are in today's purchasing power. It also reveals the hidden risk of 'safe' assets — if a deposit's nominal rate stays below inflation for years, its real return is negative and a retiree's wealth quietly shrinks. Use real returns for all long-term planning, review whether your investments beat inflation, and don't leave too much in negative-real-return instruments. Hong Kong inflation can be tracked via the Census and Statistics Department's CPI.
What is a reasonable inflation rate for Hong Kong to use here?
The official gauge is the Composite CPI published monthly by the Census and Statistics Department. For long-term planning (retirement, long-term investing), use a longer-term average rather than a single volatile year, and keep it neutral-to-conservative; for assessing today's deposit return, use the latest year-on-year figure. Practical tips: set the inflation assumption slightly higher for a buffer; note your personal inflation (rent, education, medical) may exceed the Composite CPI; enter a negative number in deflation; and always use the latest official CPI for accuracy. Pair this with our inflation calculator to feel the long-term impact.
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References
Content review: Calculatorism Finance Team. Results are for reference only; please refer to the relevant authorities for the official figures.