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What is CPI, and how does it move the stock market?

The Consumer Price Index is the most closely watched inflation report in the U.S. Once a month, at 8:30 in the morning, it can move stocks, bonds and interest-rate expectations within seconds. Here's what it measures and how to read it like a trader.

Beginner11 min readData: August 2026 CPI
Headline CPI, 12 months to August 20260.0%

A basket of everyday spending that cost $100 a year earlier now costs about $103.40.

What's in the basket (share of spending)

Shelter 35.6%Other services 25.1%Core goods 19.2%Food 13.7%Energy 6.4%

↓ Each block's price change × its share = its slice of inflation

Where the 3.4% came from

Shelter 1.1 ptsOther services 0.8 ptsCore goods 0.1 ptsFood 0.4 ptsEnergy 1.0 pts

Headline CPI-U for August 2026, released September 11, 2026. Basket shares are BLS relative importance weights. The slices are estimates and add up to about the official figure.

The latest CPI report

Consumer prices rose 0.4% in August 2026 after seasonal adjustment, and 3.4% over the past 12 months. Core CPI rose 0.3% in the month and 2.4% over the year.

Energy was the big driver. Gasoline jumped 3.9% in August and accounted for over a third of the month's increase. Gasoline is up 27.4% from a year ago, while core goods are barely rising.

That gap matters. With headline inflation well above the Fed's 2% goal, the Federal Reserve raised its target range by a quarter point to 3.75% to 4% on September 16, saying inflation "remains elevated."

Category1-month change (SA)12-month change
All items (headline CPI)0.4%3.4%
All items less food and energy (core CPI)0.3%2.4%
Energy2.1%16.3%
Gasoline (all types)3.9%27.4%
Food0.1%2.7%
Shelter0.3%3.0%
Core goods (commodities less food and energy)0.1%0.7%
Used cars and trucksn/a−2.3%

August 2026 CPI-U, released September 11, 2026 by the BLS. Next release: Wednesday, October 14, 2026 at 8:30 a.m. ET (September data). SA means seasonally adjusted.

What CPI measures

Each month, the Bureau of Labor Statistics (BLS) prices about 80,000 items in more than 200 categories, from rent and groceries to car insurance and haircuts. It then combines them into one number that shows how much prices changed on average.

CPI-U

The headline index. Covers urban consumers, who make up over 90% of the U.S. population. This is the number in the news.

CPI-W

A subset covering households of hourly wage earners, about 30% of the population. Used to adjust Social Security benefits.

What's left out

Investments like stocks, bonds and real estate, and income or Social Security taxes. Sales and excise taxes on purchases are included.

Not every item counts equally. Weights come from surveys of what households actually spend money on, so rent matters much more than, say, movie tickets.

How inflation is calculated

CPI is an index, not a price. The average from 1982 to 1984 is set to 100. An index of 110 means prices are 10% higher than in that period. The inflation rate you hear in the news is the percentage change in that index.

Inflation rate=(Index now − Index a year ago)÷Index a year ago × 100
333.918CPI-U index, July 2026
323.048CPI-U index, July 2025
3.4%(333.918 − 323.048) ÷ 323.048

Not seasonally adjusted. Monthly changes in the news are usually seasonally adjusted, which removes regular patterns like holiday sales.

Try it yourself

Build your own CPI

Each block's weight is fixed at its real share of the basket. Change how fast each block's prices are rising and watch headline and core CPI update.

Shelter (35.6% of basket, in core)Rent and owners' equivalent rent

3.0%

Other services (25.1% of basket, in core)Medical care, car insurance, travel, education and more

3.0%

Core goods (19.2% of basket, in core)Cars, clothes, furniture, appliances

0.7%

Food (13.7% of basket)Groceries and eating out

2.7%

Energy (6.4% of basket)Gasoline, electricity, natural gas

16.3%
3.4%Headline CPI (all items)
2.4%Core CPI (excludes food and energy)
+1.4 ptsGap to 2%

Each block's slice of headline inflation

Faded blocks are pulling inflation down. Weights are BLS relative importance from December 2025, so results are close to, but not exactly, the official figures.

Headline (3.4%) is well above core (2.4%). Food or energy is doing the damage. Markets often look through energy spikes, but the Fed worries if they start pushing up other prices.

Headline vs core CPI

Headline CPI includes everything. Core CPI removes food and energy, because their prices jump around with weather, wars and supply shocks. Core gives a clearer view of the underlying trend, which is what decides where inflation is heading.

Right now the two tell different stories. Headline is 3.4%, pushed up by energy. Core is 2.4%, much closer to normal. Traders and the Fed watch both, and worry most if energy costs start spreading into core prices like transport and airfares.

Many traders also follow "supercore" inflation, which is core services excluding housing. It tracks labour-heavy services like medical care and insurance, which tend to move with wages.

The trend

3.4%Aug 26
0%1%2%3%4%5%Fed's 2% goal (measured with PCE)4.2%Aug 24Aug 26

CPI-U, all items, 12-month change, not seasonally adjusted. The jump from March 2026 followed the spike in gasoline prices.

How CPI moves the stock market

CPI matters to stocks mainly through one channel: interest rates. The Fed's job includes keeping prices stable. When inflation runs hot, it may keep rates high or raise them. When inflation cools, it may cut.

Markets don't wait for the Fed. On CPI morning, traders instantly adjust their bets on future rate moves, and those bets ripple into bond yields, the dollar and stock prices. Federal Reserve research found that market reactions to CPI releases grew much stronger during the 2021 to 2023 inflation surge, when investors were paying close attention to inflation.

CPI day: the surprise is what moves markets

Suppose economists expect core CPI to rise 0.3% this month. Move the actual reading and follow the typical chain reaction.

The dataHotter than expectedCore CPI 0.5% vs 0.3% forecast
The Fed outlookRate expectations riseTraders price in higher rates for longer
Bond marketTreasury yields riseBonds sell off, especially 2-year notes
Stock marketStocks often fallGrowth and tech shares are usually hit hardest
+0.2 ptsSurprise vs forecast
6.0%Rough annual pace if this repeated monthly

Nothing here is a rule. A hot report can be shrugged off if one category did all the damage or if the Fed was already expected to act. The bigger and broader the surprise, the more reliable the chain.

Rates and valuations

Higher rates hurt stocks in two ways. Companies pay more to borrow, and investors value future profits less, since safe bonds pay more. The second effect is easy to see with a simple example.

Why higher rates hit growth stocks harder

Both companies will earn $100 in total over 10 years. Steady Co earns it in the first 5 years, Rocket Co in the last 5. Raise the interest rate investors use to value future profits.

Steady Co
$84.2
Rocket Co
$63.0
−5.4%Steady Co value vs a 4% rate
−14.0%Rocket Co value vs a 4% rate

Money earned far in the future is worth less today when rates are high, because you could earn that interest elsewhere in the meantime. Companies whose profits are mostly years away, often tech and other growth stocks, lose more value when hot inflation pushes rates up.

Who tends to win and lose

These are tendencies, not rules. Every inflation episode is different, and company-specific news often matters more.

Often hurt by hot CPI

Growth and tech stocks

Much of their value depends on profits far in the future, which are worth less when rates rise.

Often hurt by hot CPI

Rate-sensitive sectors

Homebuilders, real estate and utilities borrow heavily or compete with bonds for income-seeking investors.

Often hurt by hot CPI

Consumer discretionary

Retailers, restaurants and travel companies can suffer when rising prices squeeze household budgets.

Sometimes hold up better

Energy and materials

When inflation is driven by oil and commodities, the companies selling them can benefit from higher prices.

Sometimes hold up better

Companies with pricing power

Businesses that can raise prices without losing customers can protect their profit margins.

Mixed

Banks

Higher rates can widen lending margins, but they can also slow loan demand and raise credit risk.

CPI release day

Days beforeForecasts are setEconomists publish their expected monthly and yearly changes for headline and core CPI. This is the bar the data has to beat.
8:30 a.m. ETBLS publishes the reportThe data comes out before the stock market opens. Futures, Treasury yields and the dollar react within seconds.
8:30 to 9:30 a.m.Traders read the detailsCore month over month first, then shelter, energy and services. Early moves can reverse as the details sink in.
9:30 a.m. ETStock market opensStocks open at prices that already reflect the report. Rate-sensitive sectors often move the most.
Days afterThe Fed and other dataFed officials comment, PPI and PCE inflation follow, and the market decides how much the CPI print really changes the rate outlook.

How to read a CPI report, step by step

Compare core month over month with the forecastThis is the number markets react to most. A miss of 0.1 point matters.
Check headline and yearly ratesThey show the bigger picture and are what the news headlines quote.
Look at shelterIt's over a third of the basket and moves slowly, so it shapes the trend for months.
Separate energy from everything elseAn energy-driven jump is different from broad price increases. Check whether core goods and services are speeding up too.
Connect it to the FedAsk how the report changes the odds of the next rate decision. That's what ultimately moves stocks.

CPI vs PCE vs PPI

MeasurePublished byWhat it tracksWhy it matters
CPIBureau of Labor StatisticsPrices urban consumers pay out of pocketFirst major inflation report each month, biggest market mover
PCE price indexBureau of Economic AnalysisPrices of all consumer spending, including what employers and government pay for, like health careThe measure the Fed uses for its 2% goal
PPIBureau of Labor StatisticsPrices businesses receive for their goods and servicesEarly signal of cost pressures that may reach consumers

CPI and PCE usually move in the same direction, but PCE tends to run a little lower, partly because housing has a smaller weight in it.

Things to take care of

It's an average, not your inflation

Your own cost of living depends on what you buy. A renter who drives a lot has felt 2026's gas spike far more than the average.

Shelter lags real rents

BLS re-prices each sampled rental unit only every six months, so changes in market rents show up in CPI gradually.

Monthly numbers are noisy

One month can be distorted by a single category. Watch three- and six-month trends too.

Seasonal factors get revised

Seasonally adjusted figures can be revised for up to five years, so past monthly changes can shift slightly.

Data gaps happen

No October 2025 CPI was published because BLS couldn't collect prices during the federal government shutdown.

Market reactions can reverse

The first move after 8:30 a.m. often fades or flips once traders digest the details. Fed research suggests markets can overreact to heavily watched releases.

Common mistakes

Watching only the yearly headline

Markets trade the monthly core number against the forecast. The yearly rate changes slowly and is mostly known in advance.

Forgetting the forecast

A 0.4% increase is good news if 0.6% was expected and bad news if 0.2% was expected.

Thinking falling inflation means falling prices

Lower inflation means prices are rising more slowly. Prices only fall when inflation turns negative, called deflation.

Treating one report as a trend

One hot month after several cool ones may be noise. Look at the direction over several months.

Assuming hot CPI always sinks stocks

If strong growth comes with it, or the Fed was already expected to act, stocks can shrug it off.

Check yourself

Why does core CPI leave out food and energy?

Core CPI was expected to rise 0.2% and came in at 0.4%. What's the most typical first market reaction?

Frequently asked questions

Monthly, usually around the middle of the month, at 8:30 a.m. Eastern time. The BLS publishes the full schedule a year ahead. The September 2026 report is due October 14, 2026.

The Fed aims for 2% inflation over the longer run, measured with the PCE price index. CPI usually runs a bit above PCE, so CPI near 2% to 2.5% is generally seen as consistent with the goal.

It's over a third of the CPI basket. Because it changes slowly, it can keep inflation high or low for months.

Mainly through interest rates. Higher inflation can mean higher rates, which tends to weigh on stocks and lower the value of existing bonds. Inflation also erodes the buying power of cash.

Not exactly. CPI measures average price changes for a fixed basket. Your personal cost of living depends on what and where you buy.

Related terms

University of Michigan consumer sentimentFederal Reserve rate decisionsPCE price indexTreasury yieldsWhat is the P/E ratio?What is the PEG ratio?

Sources

This guide was written using the following references. Latest figures are from the BLS release of September 11, 2026. Basket shares are BLS relative importance weights for December 2025. Contributions in the hero and lab are Stockwhiz estimates (weight × 12-month change). The sector tendencies describe common market patterns, not guarantees.

Sources and further reading

Stockwhiz Guides is for education only and isn't investment advice. Examples use made-up companies unless marked as live data.