A savings rate tells you how many more dollars you will have; the real rate of return tells you whether those dollars will buy more. With consumer prices up 3.74% in the 12 months to September 2026 and 13-week Treasury bills yielding 4.08% on October 30, 2026, cash was ahead of inflation by about a third of a point before tax and behind it after tax. For the full menu of low-risk places to hold cash, start at the safe investments hub.
What is the real rate of return?
The real rate of return is the percentage change in what your money can buy, after removing inflation from the nominal return your account or investment pays.
The nominal return is the number on the statement: the APY on a savings account, the investment rate on a Treasury bill, the yield on a CD. It counts dollars. The real return counts purchasing power, measured with a price index, usually the Consumer Price Index for All Urban Consumers (CPI-U) published by the Bureau of Labor Statistics (BLS).
Two inputs have to line up. The nominal figure should be a full year's return with compounding counted, which is what an APY measures; a bill's investment rate is a simple annual rate that sits slightly below its APY, and the APY vs APR guide shows the conversion. And inflation should cover the same months as the return, which is the hard part: a yield is quoted for the months ahead, while the CPI reports the months behind. The same logic explains why the risk-free rate can be positive in dollars and negative in purchasing power at the same time.
How do you calculate the real rate of return?
Divide one plus the nominal return by one plus inflation, then subtract one; subtracting inflation from the nominal return gives a quick approximation.
The exact version is known as the Fisher equation, after the economist Irving Fisher:
Real return = (1 + nominal return) ÷ (1 + inflation rate) − 1
The shortcut most people use in their heads:
Real return ≈ nominal return − inflation rate
The two differ because inflation erodes the interest as well as the original deposit. The gap is roughly the real return multiplied by the inflation rate, so it is negligible when both rates are low and widens when inflation runs hot.
Worked example: A 4.08% T-bill against 3.74% inflation
On October 30, 2026, the 13-week Treasury bill had an investment yield of 4.08%. The CPI-U rose 3.74% in the 12 months to September 2026, from an index of 324.80 to 336.94.
- Exact: 1.0408 ÷ 1.0374 − 1 = 0.00328, a real return of 0.33%
- Shortcut: 4.08% − 3.74% = 0.34%
- On $10,000: the balance grows to $10,408, which buys what $10,408 ÷ 1.0374 = $10,032.77 bought a year earlier, a real gain of about $33
Rolling four 13-week bills at 4.08% would compound to about 4.14% over a year, which lifts the real return to 0.39%; the examples on this page use the quoted 4.08% to keep the arithmetic simple. Both versions assume new bills keep paying 4.08% and the next 12 months of inflation match the last 12. Neither is known in advance.
The shortcut breaks down when prices move fast. In June 2022 the CPI-U was 9.1% higher than a year earlier, the largest 12-month increase since November 1981, while the 3-month Treasury yield averaged about 1.54% that month.
Worked example: June 2022, when the shortcut misleads
- Exact: 1.0154 ÷ 1.091 − 1 = −0.0693, a real return of −6.93%
- Shortcut: 1.54% − 9.1% = −7.56%
- The shortcut overstated the loss by 0.63 percentage points
For a period longer than a year, work with totals rather than annual averages: divide the ending balance by the starting balance, divide that result by the ending CPI over the starting CPI, and subtract one.
What does the latest CPI data show?
The CPI-U rose 3.74% in the 12 months to September 2026, up from 3.40% in August, according to index levels BLS published on October 14, 2026.
BLS rounds the headline to 3.7%; the 3.74% is computed from the published index levels, 336.94 ÷ 324.80 − 1. The table below refreshes monthly. The first row is the newest month, the index column is the price level (1982–84 = 100), and the last column, the change from a year earlier, is the number that goes into the real return formula.
| Month | CPI-U index | Change from a year earlier |
|---|---|---|
| Sep 2026 | 336.940 | +3.7% |
| Aug 2026 | 334.980 | +3.4% |
| Jul 2026 | 333.918 | +3.4% |
| Jun 2026 | 333.952 | +3.5% |
| May 2026 | 335.123 | +4.2% |
| Apr 2026 | 333.020 | +3.8% |
| Mar 2026 | 330.213 | +3.3% |
| Feb 2026 | 326.785 | +2.4% |
| Jan 2026 | 325.252 | +2.4% |
| Dec 2025 | 324.054 | +2.7% |
| Nov 2025 | 324.122 | +2.7% |
| Sep 2025 | 324.800 | +3.0% |
| Aug 2025 | 323.976 | +2.9% |
Three details change how the table reads:
- There is no October 2025 row. A lapse in federal funding halted BLS price collection from October 1 to November 12, 2025, and BLS never published an all-items index for that month, so no 12-month change can be computed against it either.
- The headline hides wide spreads. In September 2026 energy was up 20.4% over 12 months and gasoline 34.2%, while food rose 2.5% and prices excluding food and energy 2.6%. A household that drives long distances felt more than the average.
- These figures are not seasonally adjusted, which suits year-over-year comparisons. The seasonally adjusted monthly change, 0.6% in September, answers a different question.
The October 2026 CPI is due on November 10, 2026.
How often has cash beaten inflation since 2000?
Cash has beaten inflation in fewer than half of all months since January 2000, judged by the 3-month Treasury yield against the 12-month CPI change.
Both lines below are monthly figures starting in January 2000: the average yield on 3-month Treasuries and the 12-month change in consumer prices.
- 3-month Treasury yield, monthly average
- CPI inflation, 12-month change
| Measure | Yield | Month |
|---|---|---|
| Latest monthly average | 4.23% | Oct 2026 |
| A year earlier | 3.98% | Oct 2025 |
| Average over the last 10 years | 2.55% | |
| Average since 2000 | 2.00% | |
| Highest month | 6.36% | Nov 2000 |
| Lowest month | 0.01% | Dec 2011 |
| Months the yield beat CPI inflation | 18 of 20 (90%) |
The last row of the table under the chart, "Months the yield beat CPI inflation," counts the months in which the average 3-month yield topped the 12-month CPI-U change for the same month, out of all months with both figures. Read it with five caveats:
- It pairs a yield you could lock in that month with inflation over the previous 12 months. What a bill really earned depended on inflation over the next three months, which nobody knew at the time.
- It is before tax. Apply a 22% federal rate to each month's yield and more than a quarter of the winning months through September 2026 become losing ones.
- It counts months, not margins. A month when cash won by 0.02 points counts the same as June 2022, when it lost by more than seven.
- Falling prices count as wins. The CPI-U was below its year-earlier level from March to October 2009, so a yield averaging 0.15% that year still came out ahead.
- Months with no CPI figure, such as October 2025 and the newest month of yields, are left out.
The long runs matter more than the overall share. Here are the main stretches in the same Treasury and BLS data:
| Stretch | Months compared | Average 3-month yield | Average 12-month CPI | Result |
|---|---|---|---|---|
| Jan 2000 to Jul 2002 | 31 | 4.06% | 2.69% | Ahead every month |
| Oct 2002 to Apr 2005 | 31 | 1.41% | 2.54% | Behind every month |
| Nov 2005 to Oct 2007 | 24 | 4.72% | 2.99% | Ahead every month |
| Nov 2009 to Dec 2014 | 62 | 0.07% | 2.01% | Behind every month |
| Oct 2015 to Oct 2018 | 37 | 0.93% | 1.82% | Behind every month |
| Jun 2020 to Mar 2023 | 34 | 1.20% | 5.24% | Behind every month |
| Apr 2023 to Mar 2026 | 35 | 4.82% | 3.01% | Ahead every month |
| Apr 2026 to Sep 2026 | 6 | 3.84% | 3.67% | Behind in April and May, ahead from June |
Policy explains most of the losing runs. The Federal Reserve held its target range near zero from late 2008 until December 2015, and again from March 15, 2020 to March 16, 2022, while prices kept rising. Cash pulled ahead when the Fed held short-term rates above inflation, as in 2006–2007 and from spring 2023; the guide to Fed decisions and bill rates explains that link.
Worked example: $10,000 kept in 3-month bills from 2000 to 2026
Method: roll the money every month at that month's average 3-month yield, so each month earns the yield ÷ 12. This approximates a bill ladder that is always reinvested.
- Nominal value by September 2026: about $17,036, before tax
- CPI-U: 168.3 in December 1999 and 336.94 in September 2026, so prices rose 100.2%
- Real value: $17,036 ÷ 2.002 = about $8,510 in December 1999 dollars, a real loss of about 15%
- With 22% tax taken from each month's interest: about $15,154, or $7,570 in 1999 dollars, a real loss of about 24%
- Annualized: 2.01% nominal against 2.63% inflation, about −0.60% a year in real terms before tax
What is your real return after taxes?
Subtract tax from the nominal yield first, then remove inflation, because tax is charged on all of the interest, including the part that only offsets rising prices.
After-tax real return = (1 + yield × (1 − tax rate)) ÷ (1 + inflation rate) − 1
That is why a modest real gain before tax often becomes a loss after it.
Worked example: After-tax real return on a 4.08% bill in the 22% bracket
For 2026, the 22% federal bracket applies to taxable income over $50,400 up to $105,700 for single filers, and over $100,800 up to $211,400 for married couples filing jointly.
- After-tax yield: 4.08% × (1 − 0.22) = 3.18%
- After-tax real return: 1.031824 ÷ 1.0374 − 1 = −0.54%
- On $10,000: $408 of interest, $89.76 of federal tax, $10,318.24 left, which buys what $9,946.25 bought a year earlier
- Break-even: a fully taxable yield must reach 3.74% ÷ 0.78 = 4.79% just to keep pace with 3.74% inflation
Where the money sits changes the tax bill. Treasury bill interest is taxed federally but not by states or cities, while bank interest is generally taxed by both. In a state with a 5% income tax, 4.08% earned in a bank account keeps about 2.98% after both taxes, a real return near −0.73%, and the break-even yield rises to about 5.12%. Those figures ignore deductions and credits, and tax rules change, so check your own numbers with a tax professional. The T-bill tax guide covers the state exemption, and an IRA or other tax-deferred account postpones the drag.
Which investments quote a real return directly?
Treasury Inflation-Protected Securities and Series I savings bonds both state a real rate, because their payments rise with the CPI-U.
A TIPS yield is a real yield. On October 30, 2026, the 10-year TIPS yielded 2.60% while the ordinary 10-year Treasury note yielded 4.94%. The 2.34-point gap is the breakeven inflation rate: the average CPI inflation at which the two bonds would end up earning the same. Holding TIPS to maturity secures that real yield before tax, but the price moves in between, as the TIPS guide explains.
I bonds work differently. Their fixed rate, 1.40% for bonds bought from November 1, 2026 to April 30, 2027, works as a real return that lasts for the life of the bond, while an inflation component resets every six months. Together they make the current composite rate of 5.51%, and purchases are limited to $10,000 in electronic I bonds per person per calendar year. The I bonds guide covers the formula and the penalty for cashing early.
Savings accounts, CDs, money market funds and ordinary Treasury bills pay nominal rates only, so the conversion is up to you.
How do you compare cash options in real terms?
Put every option on the same footing, compounded, after tax and against the same inflation assumption, before you compare them.
Convert each quote to an APY
Bank accounts already quote APY. Convert a bill's investment rate or a CD's interest rate so compounding is counted the same way everywhere.
Take out the taxes that apply
Multiply by one minus your federal rate, and by one minus your state rate unless the interest comes from Treasuries.
Choose one inflation assumption
Use the latest 12-month CPI change for a rough check, or a TIPS breakeven rate for a market estimate, and apply it to every option.
Run the Fisher formula
Divide one plus the after-tax yield by one plus inflation and subtract one. Rank on that number, then weigh access, insurance and lock-up periods.
Recheck when the inputs move
Bill yields change daily on the T-bill rates page and CPI monthly, so a ranking can flip within a quarter.
To project the result over many years, enter an after-tax real rate into the compound interest calculator; the compound interest guide explains how that growth builds. The Treasury bill calculator turns a bill's discount rate into dollars.
What are the risks of relying on a real-return estimate?
The main risk is that the inflation figure you plug in turns out wrong, because a real return can only be measured once the holding period is over.
- Inflation surprise. The 3.74% figure looks backward. If prices rise 5% over the next year instead, the 4.08% bill's real return is about −0.88% before tax and −1.73% after a 22% tax.
- Your basket is not the index. The CPI-U is an average for urban consumers. Heavy spending on energy, insurance or medical care can push personal inflation well above it.
- Reinvestment risk. A 13-week bill locks its yield for only 13 weeks. If short-term rates fall, the next bill pays less while prices keep rising. The guide to whether Treasuries are risk-free covers the risks that remain despite the full faith and credit of the US government.
- Small losses compound. A real return of −0.54% a year looks harmless, but over 10 years it cuts purchasing power by about 5.2%. The rule of 72 gives a quick estimate of how fast inflation halves a balance.
- I bonds are hard to exit early. Not cashable for 12 months; cashing before 5 years forfeits the last 3 months of interest. TIPS have the opposite catch: they can be sold any day, but possibly for less than you paid.
- Tax rules and brackets shift. A raise that moves you into the 24% bracket lifts the break-even yield, and state rates differ widely.
For a wider map of these hazards, see the types of investment risk. None of the figures above is a forecast; they show how to measure a real return once you choose your inputs.