Head-to-head
Nominal vs Real Return
A return quoted without a reference point is a number about money, not about purchasing power. Ten percent a year sounds like progress until you notice prices rose 3% over the same period, at which point the honest figure is 6.80%. Nominal returns measure the account; real returns measure what the account can buy.
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The conversion is not subtraction, though subtraction is close enough to be tempting. Dividing (1 + nominal) by (1 + inflation) is the Fisher relationship, and it exists because both rates compound. Subtracting gives 7.00% where the exact answer is 6.80% — a small gap at low rates that widens quickly as either number grows.
The gap compounds too. Over five years the difference between 7.00% and 6.80% is about $150 on a $10,000 stake, which is not nothing, and at 12% nominal with 6% inflation the subtraction error is a third of a point a year.
Which one to use depends on the question. Comparing two investments over the same period, nominal is fine because inflation cancels. Comparing an investment against a future cost — retirement spending, a house, school fees — only the real figure answers it.
Nominal
How To Calculate CAGR
CAGR compresses a messy multi-year history into one smooth annual rate. Because it reports the same kind of number for a seven-year stock hold and a five-year revenue line, it is the standard way to put two very different histories on one scale.
Real
How To Calculate Inflation Adjusted Value
Inflation quietly erodes the buying power of money. A sum held in cash loses value every year even though its number stays the same. This calculator converts between nominal amounts and real, inflation-adjusted amounts so you can compare figures honestly across time.
How They Differ
| Attribute | Nominal | Real |
|---|---|---|
| What it measures | Growth of the account balance | Growth of purchasing power |
| Formula | End ÷ Start − 1 | (1 + nominal) ÷ (1 + inflation) − 1 |
| Quick approximation | The figure itself | Nominal minus inflation, slightly too high |
| 10% nominal, 3% inflation | 10.00% | 6.80% |
| Effect of inflation | Ignored entirely | Removed from every year |
| Comparing two assets | Fine — inflation cancels | Also fine, and the ranking is identical |
| Comparing against a future cost | No, it overstates what you can buy | Yes, that is the whole point |
| Typical use | Quoted fund returns and savings rates | Retirement planning, real wage growth |
The Same Numbers, Both Ways
$10,000 invested at 10% a year for five years, with inflation running at 3% over the same period.
- Starting amount
- $10,000
- Nominal return
- 10% a year
- Inflation
- 3% a year
- Years
- 5
| Line | Nominal | Real |
|---|---|---|
| Growth rate | 10.00% | 6.80% |
| Value after five years | $16,105 | $13,892 |
| Gain | $6,105 | $3,892 |
| Eaten by inflation | $0 | $2,213 |
| Quick subtraction gives | 10.00% | 7.00% |
| Error in that shortcut | 0.00% | 0.20% |
| Years to double | 7.27 | 10.54 |
At 10.00% the account grows to $16,105 in five years, but prices rose 3.0% a year, so in today's money that is $13,892 — a real return of 6.80%, with $2,213 of the gain consumed by inflation. Subtracting the two rates gives 7.00%, which is 0.20% too generous.
When To Use Each
Nominal
- You are comparing two investments over the same period, where inflation affects both equally.
- You are quoting a published return, a savings rate or a fund fact sheet.
- The holding period is short enough that inflation barely moves the answer.
Real
- You are testing whether a portfolio will fund a future expense measured in future prices.
- You are comparing returns across countries or decades with very different inflation.
- You want to know whether your standard of living actually improved.
Common Questions
Why not just subtract inflation?
Because both rates compound. Dividing (1 + nominal) by (1 + inflation) is exact; subtracting is a first-order approximation that always errs on the generous side. At 10% and 3% the error is 0.20 points, and at 20% and 10% it is nearly a full point.
Is the real return the same as the inflation-adjusted value?
They are two views of one calculation. The real return is a rate; the inflation-adjusted value is a balance expressed in today's money. Discounting the future balance at the inflation rate and compounding the starting balance at the real rate give the same answer.
Which inflation measure should I use?
The one that matches the spending you are modelling. A headline consumer price index is fine for general purchasing power; for retirement, a measure weighted towards health and housing is closer to the truth. Using a mismatched index is a bigger error than the subtraction shortcut.
Can the real return be negative?
Yes, whenever inflation exceeds the nominal return — which is normal for cash in a savings account during a high-inflation period. That is not a loss in the account; it is a loss in what the account can buy, and only the real figure shows it.
Does this apply to wages?
Exactly the same way. A 4% raise with 5% inflation is a 0.95% cut in real pay. It is the most common place the distinction is quietly dropped, because nominal raises are what appear on the letter.
More Comparisons
- ROI vs CAGR
ROI measures the whole return; CAGR turns it into a compound annual rate. A 100% return over five years is 20% a year by division but 14.87% a year in reality.
- Revenue Growth Rate vs CAGR
Revenue going from $1.2M to $2.5M over five years is 108.33% of growth, 21.67% a year if you divide, and 15.81% a year if you compound. Compounding the 21.67% would predict $3.2M — revenue the business never had.
- Simple Interest vs Compound Interest
Simple interest charges the principal only; compound interest charges the balance. On $10,000 at 5% over 10 years that gap is $1,288.95 — here is where it comes from.
Sources
- Real versus nominal value — the Fisher relationship — Wikipedia
- Consumer Price Index — how inflation is measured — U.S. Bureau of Labor Statistics
- Inflation and returns — investor guidance — U.S. Securities and Exchange Commission
Both methods sit in Finance.