Investment Return Calculator
Model the nominal and real inflation-adjusted value of any investment over time, so you can see what your returns are actually worth in purchasing power.
years
Enter your values above to see the results.
Tips & Notes
- ✓Target a real return above inflation rather than a nominal return target — a 7% return in a 5% inflation environment is only 2% real growth.
- ✓Treasury Inflation-Protected Securities (TIPS) guarantee a fixed real return above inflation — valuable for the portion of a portfolio meant to preserve purchasing power.
- ✓The historical real return of the US stock market is approximately 7% nominal minus 3% average inflation, producing roughly 4% real return over long periods.
- ✓Social Security benefits are inflation-adjusted, which is one reason delaying claiming to maximize the inflation-protected benefit is valuable for long-term retirement planning.
- ✓In high-inflation environments, holding excess cash is not safe — cash loses purchasing power at the inflation rate every year with zero offsetting return.
- ✓Consider allocating a portion of a retirement portfolio to real assets like real estate, commodities, or TIPS that historically maintain value relative to inflation.
Common Mistakes
- ✗Planning retirement income needs in today dollars without inflation-adjusting — a $5,000/month need today requires $9,030/month in 20 years at 3% annual inflation.
- ✗Treating a 7% nominal return as a 7% real return — at 3% inflation, the real purchasing power grows by only approximately 4% per year.
- ✗Not increasing contribution amounts over time — keeping monthly contributions flat in nominal terms means contributions shrink in real purchasing power each year.
- ✗Holding large cash reserves during high inflation periods — cash loses purchasing power at the inflation rate with no compensating return.
- ✗Ignoring inflation in short-term plans under 5 years — even at 3% inflation, $100,000 in 5 years is worth only $86,261 in today purchasing power.
- ✗Using the same inflation rate for all expense categories — healthcare inflation historically runs 2-3% above general inflation, significantly affecting retirement cost projections.
Investment Return Calculator Overview
An investment return calculator shows two versions of your portfolio's future: the nominal value (what your account statement will say) and the real value (what that money will actually buy). The gap between these two numbers is inflation — and over long investment periods, it is substantial.
A $1,000,000 portfolio in 30 years at 3% annual inflation is worth only $412,000 in today purchasing power. Planning with only the nominal number leads to retirement shortfalls that are entirely avoidable with proper inflation adjustment.
What each field means:
- Initial Investment — the starting portfolio value in today dollars
- Monthly Contribution — regular additions; entered in today dollars, so real contributions stay constant
- Annual Return — expected nominal return before inflation adjustment
- Inflation Rate — expected annual price increase; 2-3% is the historical US average
- Years — the investment horizon; inflation impact grows dramatically with time
What your results mean:
- Nominal Value — the raw portfolio total your account will show at the end of the period
- Real Value — the nominal value converted to today purchasing power after inflation is removed
- Total Contributions — all money you put in across the full period
- Total Growth — the increase above contributions in nominal terms
- Inflation Impact — the dollar difference between nominal and real value; what inflation cost you
Example — $25,000 initial, $600/month, 7% return, 3% inflation, 25 years:
Nominal future value: $642,477 Real future value (today dollars): $308,274 Inflation cost: $334,203 in purchasing power lost to inflation Total contributed: $205,000 Real return above contributions: $103,274 The portfolio shows $642,477 but only feels like $308,274 in today money. Real annual return (after inflation): 7% - 3% = approximately 4% per year.
EX: How inflation rate changes the real value of the same portfolio ($500k nominal in 20 years) 1% inflation: real value $409,964 (lose $90,036 to inflation) 2% inflation: real value $336,706 (lose $163,294 to inflation) 3% inflation: real value $276,897 (lose $223,103 to inflation) 4% inflation: real value $228,193 (lose $271,807 to inflation) Each additional 1% of inflation costs roughly $60,000-$80,000 in purchasing power on $500,000 over 20 years.
Real vs nominal return — $10,000 initial, $300/month, 7% nominal return:
| Inflation Rate | Nominal Value (20yr) | Real Value (20yr) | Purchasing Power Lost |
|---|---|---|---|
| 2% | $194,697 | $131,107 | $63,590 |
| 3% | $194,697 | $107,903 | $86,794 |
| 4% | $194,697 | $88,869 | $105,828 |
Real return by nominal return and inflation — 20-year horizon:
| Nominal Return | 2% inflation | 3% inflation | 4% inflation |
|---|---|---|---|
| 5% | 2.94% real | 1.94% real | 0.96% real |
| 7% | 4.90% real | 3.88% real | 2.88% real |
| 9% | 6.86% real | 5.83% real | 4.81% real |
The Fisher equation approximates real return as nominal return minus inflation rate — so 7% nominal at 3% inflation is approximately 4% real. The precise formula is: real return = (1 + nominal) / (1 + inflation) - 1. The approximation works well for low rates but understates the real return when both rates are high. For retirement planning, always target a specific real return above inflation rather than a nominal return target — it is the only way to ensure purchasing power is actually preserved.
Frequently Asked Questions
The real rate of return is the nominal return minus the inflation rate, representing the actual increase in purchasing power. The precise formula is: real return = (1 + nominal return) / (1 + inflation rate) - 1. For a 7% nominal return at 3% inflation: real return = (1.07 / 1.03) - 1 = 3.88%. The approximation of simply subtracting inflation from the nominal rate (7% - 3% = 4%) is close but slightly overstates the real return. For retirement planning and long-term wealth goals, the real return is what matters — it measures whether purchasing power is actually growing.
Inflation reduces the purchasing power of every future dollar. Over long periods, the effect is dramatic. At 3% annual inflation: $100 today equals $134 in 10 years, $181 in 20 years, and $243 in 30 years — meaning your money must grow by those amounts just to maintain current purchasing power. For a $1,000,000 retirement target in 30 years, you actually need $1,000,000 in future dollars, but those future dollars only buy what $412,000 buys today at 3% inflation. This is why retirement planning must account for inflation rather than targeting a nominal dollar amount.
Historically, diversified equity portfolios have delivered real returns of approximately 6-7% before fees. After a typical 0.5% in expense ratios and 0.5% in behavioral costs, net real returns for disciplined equity investors have been approximately 5-6%. Bonds have delivered much lower real returns, often 1-2% above inflation. Cash and savings accounts frequently deliver negative real returns during inflationary periods. For retirement planning, targeting a 4-5% real return on a diversified portfolio is a reasonable and historically achievable assumption.
Several asset classes have historically maintained purchasing power during inflationary periods. Equities: company revenues and earnings tend to grow with inflation over time, making broad equity index funds effective long-term inflation hedges. Real estate: property values and rents typically rise with inflation. TIPS: Treasury Inflation-Protected Securities explicitly adjust principal with CPI, guaranteeing a fixed real return. Commodities: physical goods tend to increase in price during inflation. I-Bonds: US savings bonds that adjust for inflation up to a fixed annual purchase limit. No single asset class protects perfectly in all inflationary environments.
The US Federal Reserve targets 2% annual inflation as its long-term goal. Historical US inflation has averaged approximately 3% over the past century, with significant variation across periods. For conservative planning, using 3% general inflation is reasonable. For healthcare expense planning in retirement, use 4-5% since medical costs have historically inflated faster than general prices. For specific goals like college tuition, education inflation has averaged 4-6% annually. Building in a 3% inflation assumption for general living expenses provides a reasonable buffer against most realistic inflationary scenarios.
Use real returns for long-term planning whenever possible — they directly answer whether purchasing power is growing. If you plan in nominal returns with nominal expense projections, both the asset side and the liability side of the equation are inflated by the same factor, and the plan may still work out correctly. Problems arise when planners use nominal portfolio projections but forget to inflate future expense needs by the same factor. The safest approach: plan with real returns and today-dollar expense estimates throughout. This eliminates inflation as a source of planning error and produces targets that are directly interpretable in current purchasing power.