What Is CPI? How Inflation Data Moves the Forex Market

Once a month, a report about the price of rent, bread and petrol can move EUR/USD by more than a normal day’s range in a few minutes. If you trade currencies, you need to know what that report is, why the market cares so much, and how to stay safe when it lands.

Quick answer: CPI, the consumer price index, measures how fast the prices of everyday goods and services are rising. In forex, CPI matters because inflation steers interest rates: a print above the forecast makes rate rises more likely and usually lifts the currency, while a print below it usually weakens it. The gap between actual and forecast moves the market.

What is CPI? The consumer price index in plain English

Inflation is the rate at which prices in an economy rise over time. The consumer price index, or CPI, is the most widely watched way of measuring it. Statisticians track the prices of a fixed basket of goods and services that a typical household buys, from rent and electricity to food, fuel, clothes, haircuts and holidays, and they work out how much the cost of that whole basket has changed.

A red shopping basket holding a pineapple, bananas and other groceries, standing on the floor of a supermarket aisle. — CPI follows the prices of a fixed basket of goods and services that households buy. Each item counts in proportion to how much people spend on it.

Each item is weighted by how much households actually spend on it, so a rise in rents matters far more to the index than a rise in the price of matches. In the United States, housing costs (which the statisticians call shelter) are the largest single part of the index, at roughly a third of it. Each country builds and reweights its own basket, so the UK and US indices are similar in spirit but not identical.

How the consumer price index works: prices for a weighted basket of everyday goods and services are collected each month, and the cost of the whole basket is compared with a year earlier to give the CPI inflation rate.

Each month the statistics office publishes the new index level and, more importantly for traders, the percentage change. If the basket cost 100 a year ago and costs 103 now, annual CPI inflation is 3%. That is the figure you will see in headlines and on every economic calendar.

Two official sources are worth bookmarking. In the US, CPI is produced by the Bureau of Labor Statistics. In the UK, it comes from the Office for National Statistics. Both publish release dates well in advance, along with full tables if you want to see which categories drove a given month.

For the Academy version of this section, with a short quiz at the end, see the lesson on inflation and CPI.

Headline CPI vs core CPI

Every CPI release contains at least two headline numbers, and confusing them is one of the most common mistakes new traders make.

Headline CPI covers the whole basket, everything households buy.
Core CPI strips out the most volatile items, usually food and energy. The UK and euro area versions also leave out alcohol and tobacco.

Core removes food and energy because their prices swing for reasons a central bank cannot do much about. A cold winter, a poor harvest or a jump in the oil price can push headline inflation up or down by a large amount in a single month, then reverse a few months later. Raising interest rates will not make it rain or bring down the price of crude oil. Core inflation filters out that noise and shows the underlying trend: whether price rises have spread into rents, services, wages and everyday goods, where they tend to stick.

Headline CPI measures the whole basket. Core CPI removes food and energy, whose prices swing with weather and oil, to show the underlying trend that central banks can influence.

Central banks look at both. Headline inflation is what households feel and what drives their expectations of future prices. Core inflation is a better guide to where headline will settle once temporary shocks fade. Core sometimes matters more to traders than headline. If headline CPI drops because petrol got cheaper but core inflation comes in above forecast, the market may well treat the release as hot, and the currency can rise even though the headline number fell. The reverse happens too: a headline jump driven purely by energy, with soft core, often fades quickly.

So when you look at a CPI release, read headline and core side by side, and compare each with its own forecast. If they point in opposite directions, the first spike can go one way and then reverse as traders work out which figure the central bank is likely to care about.

Month-on-month vs year-on-year: reading the numbers

CPI is reported in two time frames, and both appear on the calendar.

Year-on-year (YoY) compares the index with the same month a year ago. This is the figure central banks set their targets on, and the one you see in news headlines: “inflation rose to 3.2%”.
Month-on-month (MoM) compares the index with the previous month. A typical reading is a few tenths of a percent, such as 0.2% or 0.3%.

The monthly figure is small, but it carries a lot of information. A monthly rise of about 0.17% compounds to roughly 2% over a year, so as a rule of thumb, every extra 0.1 point on the monthly number is worth a little more than 1 point a year. That is why many traders focus on the monthly core reading: it shows what is happening to prices right now, rather than over the last twelve months.

The year-on-year figure has a quirk you need to understand, called a base effect. Because it compares with a year ago, it depends on what happened twelve months earlier as well as what is happening today. If prices jumped sharply in one month last year, perhaps because of an energy shock, the annual rate will drop abruptly when that month falls out of the twelve-month window, even though prices this month rose at a perfectly normal pace.

An illustrative base effect. Prices rise 0.2% every month except one spike of 1.0% a year ago. When that spike drops out of the twelve-month window, annual inflation falls from about 3.2% to 2.4% even though this month was ordinary.

Base effects are predictable, because anyone can see what the index did a year ago, so economists build them into their forecasts. A large base-effect drop is usually expected and does little to the currency on the day. It is one more reason to judge a release against the forecast, not against last month’s figure.

Why CPI moves the forex market

Currencies do not react to inflation because inflation is good or bad for a currency in itself. Over many years, high inflation erodes what a currency can buy. In the short run, though, the effect runs almost entirely through one channel: what inflation means for interest rates.

Most major central banks have an inflation target of 2%. The US Federal Reserve, the European Central Bank and the Bank of England all aim for 2%, although each measures it slightly differently. When inflation runs above target, the bank is under pressure to raise interest rates, or keep them high for longer, to cool spending. When inflation runs below target, it has room to cut. CPI is the clearest monthly evidence of which way that pressure is building, so every release shifts the market’s view of where rates are heading.

That shift then travels to the currency through the same chain that a rate decision does. Higher expected rates raise the yield on bonds and deposits in that currency, which attracts foreign money, which has to buy the currency first. Step through the chain below, then switch to a cut to see it run in reverse.

Inflation reaches the currency through interest rates. A hot CPI print makes rate rises more likely, which lifts yields, draws in foreign money and strengthens the currency. A cool print runs the chain in reverse.

CPI sits one step before the chain starts: it changes the expected rate path, and the market trades that expectation long before any central bank meeting. This is why traders talk about inflation data in the language of hawkish and dovish policy. A hot print is read as hawkish, pulling forward or adding expected rate rises. A cool print is read as dovish.

From CPI surprise to currency move: a print above the consensus raises expected rates and short-term bond yields, and the currency strengthens. A print below the consensus does the reverse. An in-line print changes little.

How much CPI matters also depends on the moment. When inflation is close to target and the central bank is in no hurry, CPI is just one release among many. When inflation is far from target, every print can change the rate outlook, and CPI day becomes one of the most volatile of the month. That is what happened after 2021: US CPI inflation peaked at 9.1% in June 2022 and UK CPI at 11.1% in October 2022, and for a long stretch inflation releases moved currencies as much as central bank meetings did.

Inflation is one of five big forces on any currency. Tap the drivers around the dollar below to see how inflation sits alongside rates, growth, risk mood and trade.

▲ Higher rates

▼ Lower rates

Higher interest rates attract foreign money seeking better returns, which must be converted into the currency first. Rate expectations are the single biggest driver of major currencies.

Inflation is one of five main drivers of the US dollar, and it works mostly through the interest-rate driver: rising inflation supports the dollar when it means higher rates ahead.

Our guide to how interest rates affect currency prices covers the rate side of this chain in depth, including why a currency can fall on the day rates rise. The Academy lesson on central banks explains the mandates behind the 2% targets, and what moves currencies maps all five drivers.

Surprise vs consensus: how to read a CPI release

Before every CPI release, economists at banks and research firms publish their forecasts. Calendars show the median of those forecasts, known as the consensus or simply the forecast. By the time the number comes out, the consensus is already priced in: the exchange rate has moved to reflect it. What moves the market is the surprise, the gap between the actual figure and the consensus.

That has three practical consequences.

An in-line print usually does very little, however high or low the number is in absolute terms. CPI at 4% when 4% was expected is old news.
The size of the move tends to scale with the size of the surprise. One tenth of a point above forecast might move EUR/USD a little; three or four tenths can reprice the whole rate outlook.
Last month’s figure is not the benchmark. If inflation falls from 3.2% to 3.0% but the forecast was 2.8%, the release is hot, and the currency may rise even though inflation fell.

Try it below. The simulator shows a US CPI release with a forecast of 3.1%. Slide the actual figure and watch how the verdict and the reaction sketch change.

Time	Cur.	Impact	Event	Previous	Forecast	Actual
13:30	USD	●●●	CPI (inflation, year on year)	3.2%	3.1%	—

Actual figure:

A mock US CPI release with a 3.1% forecast. Slide the actual figure: a print at the forecast barely moves EUR/USD, while a larger surprise in either direction produces a larger reaction. Reactions are illustrative.

Real releases are messier than one number, so read the whole row before you decide what the market is thinking:

Headline and core. As above, if they disagree, core often wins, especially in the US, where many traders watch the monthly core figure most closely.
Monthly and annual. A monthly figure exactly on forecast with an annual figure a tenth higher is often down to rounding or base effects. A monthly miss is usually the stronger signal.
Revisions and detail. Statistics offices sometimes revise earlier months, and analysts dig into categories such as services and rents within minutes. The first spike can reverse once that reading is done.
The bigger picture. If a central bank has already said it is about to cut, a slightly hot CPI may delay the cut rather than cancel it, and the reaction may be modest.

CPI release times and other inflation measures

CPI is published monthly in every major economy, normally around the middle of the month after the one it measures. The exact time matters, because that is when spreads widen and prices jump. Release times below are the usual pattern; always confirm the date and time on the official calendar or your own economic calendar.

Economy	Measure	Published by	Usual release time
United States	CPI	Bureau of Labor Statistics	8:30 a.m. New York time (13:30 UK time for most of the year)
United Kingdom	CPI	Office for National Statistics	07:00 UK time
Euro area	HICP	Eurostat	A flash estimate first, then a final figure later in the month
United States	PCE price index	Bureau of Economic Analysis	Later in the month, after CPI

Two other inflation measures are worth knowing by name, even if you never trade them directly.

PCE (personal consumption expenditures price index) is the US measure the Federal Reserve uses for its 2% target. It covers a broader range of spending than CPI and is weighted differently.
HICP (harmonised index of consumer prices) is the euro area’s inflation measure, built to the same method in every member country. It is the measure the European Central Bank’s 2% target refers to, so for the euro side of EUR/USD it plays the role CPI plays in the US.

Clock changes catch people out. The US and the UK move their clocks on different dates in spring and autumn, so for a few weeks a year US CPI lands at 12:30 UK time rather than 13:30. If you trade from another time zone, convert the time yourself rather than trusting memory. Our guide to forex market hours explains how the sessions line up, and the Academy lesson on the economic calendar shows how to read the previous, forecast and actual columns.

How to handle CPI day as a retail trader

You do not have to trade CPI. For most beginners the sensible first goal is to not get hurt by it. A major release changes the trading conditions for a few minutes in ways that have nothing to do with your strategy:

Spreads widen. Liquidity providers pull back just before the release, so the spread on EUR/USD can jump from under a pip to several pips for a short time.
Prices gap. The first move can skip whole price levels in a second, so there may be no trade at the exact price your order asked for.
Stops slip. A stop loss becomes a market order when triggered, and in a fast market it fills at the next available price. That difference is called slippage. Compare a calm market with a news release in the simulator below.

Requested

Filled at

Slippage

Cost on 1 mini lot

Illustrative fills in a calm market and during a news release such as CPI. Market and stop orders can fill several pips away from the requested price when prices jump; limit orders fill at your price or better, or not at all.

A simple routine keeps CPI day under control:

Check the calendar every week. Note the date and time of CPI for every currency you trade, and the consensus for headline and core.
Decide in advance what you will do with open trades. Close them, reduce them, or leave them with a stop you accept may slip. Do not decide in the last minute.
Stay flat for the release itself. Many traders avoid opening new trades from about 15–30 minutes before the release until at least 15 minutes after, when spreads have returned to normal.
If you trade the aftermath, size from the stop. Volatility stays high for a while, so stops need more room. More room means a smaller position for the same risk, never a larger risk.
Write it down. Record what the release was, how the market reacted and what you did. After a few months your journal will show how your pairs actually behave on CPI day.

The same routine works for the monthly jobs report, which lands at the same time of day as US CPI; our guide to non-farm payrolls and the lesson on jobs data and NFP apply it there. The worked example below shows how a hot US CPI print can play out in EUR/USD, and why the size of your position matters more than whether you guessed the direction right.

A steaming cup of coffee beside an open laptop on a low table in a bright, quiet living room. — Standing aside for the minutes around a CPI release is a valid plan. Spreads, gaps and slippage settle down once the first reaction has passed.

Example: a hot US CPI print and one EUR/USD trade

You have a $5,000 account and risk 1% per trade, which is $50. US CPI is due at 8:30 a.m. New York time. The calendar shows headline CPI: previous 3.2%, forecast 3.1%, and core CPI month-on-month: forecast 0.3%. EUR/USD is trading around 1.0880, and your plan says no open trades into the release.
The release: headline 3.5% and core 0.5% on the month. Both are well above consensus. Rate cuts that the market had priced start to look unlikely, and the dollar is bought. EUR/USD falls from 1.0880 to about 1.0810 within ten minutes, about 70 pips, while the spread briefly widens to several pips.
You wait fifteen minutes for spreads to settle. Price bounces to 1.0838 and stalls. You decide to sell at 1.0832, with a stop at 1.0857, above the bounce high with a buffer: 25 pips of risk. Your target is 1.0782, 50 pips away, a 2:1 reward-to-risk.
Position size: $50 ÷ 25 pips = $2 per pip. On EUR/USD a mini lot (0.10) is worth $1 per pip, so you sell 0.20 lots.
Price dips to 1.0806, then buyers return and EUR/USD climbs through 1.0857. Your stop fills: 25 pips × $2 = a $50 loss, 1% of the account, plus a little spread. Had you sold a full standard lot because the number “looked obvious”, the same stop would have cost 25 × $10 = $250, 5% of the account. The data was hot, the direction was reasonable, and the trade still lost. Position size decided how much that mattered.

Step through the same trade on the chart below. The candles are five minutes each, and the prices are illustrative.

An illustrative hot US CPI release on 5-minute EUR/USD candles: the drop on the release, a planned sell after the spreads settle, and a stop that is hit when the move reverses. The loss is the planned 1%.

The plan kept you out of the worst minutes, when spreads were widest. It placed the stop where the trade idea was wrong, not where the loss felt comfortable. And it sized the position from that stop. Our guides to where to place a stop loss and position sizing cover both steps, and the lesson on risk per trade explains why 1% is a common ceiling. The EUR/USD trading guide shows how US data like CPI fits into that pair’s wider story.

Common CPI mistakes

Comparing with last month instead of the forecast

“Inflation fell, so the currency should fall” is the most common misreading. The market had already priced the forecast. Judge every release by actual minus consensus, for headline and core separately.

Reading only the headline number

A headline figure pushed around by petrol prices can point the opposite way from core. If you react to the headline in the first second, you may be on the wrong side when the market digests core a minute later.

Placing orders just before the release

Pending orders and tight stops right next to the current price are likely to be triggered by the first spike and filled with slippage. If you have no plan for the release, the simplest plan is to be flat.

Assuming the first move is the real move

The first spike is often the largest and the least reliable. Reversals within the first hour are common once traders read the detail, as the worked example showed. Waiting costs you a few pips of the move; chasing can cost you far more.

Trading bigger because the number “looks obvious”

A large surprise feels like certainty, but hot data can still be followed by a reversal, and conditions are faster than usual. Keep your risk per trade the same on CPI day as on any other day, or lower.

Frequently asked questions

What is CPI in forex?

CPI, the consumer price index, measures how fast the prices of everyday goods and services are rising. In forex it matters because inflation shapes central bank interest rate decisions. A CPI print above the forecast usually strengthens the currency because it makes higher rates more likely; a print below the forecast usually weakens it.

Is high inflation good or bad for a currency?

In the short term, inflation that comes in higher than expected usually supports a currency, because traders expect the central bank to keep rates higher for longer. Over the long term, persistently high inflation that the central bank fails to control erodes what the currency buys and tends to weaken it.

What time is the CPI release?

US CPI is usually published at 8:30 a.m. New York time, which is 13:30 UK time for most of the year. UK CPI is usually published by the Office for National Statistics at 07:00 UK time. Both come out around the middle of the month. Always confirm the date and time on an economic calendar.

What is the difference between CPI and core CPI?

Headline CPI covers the whole basket of goods and services. Core CPI excludes the most volatile items, usually food and energy, to show the underlying trend in prices. Central banks watch core closely because it is less affected by temporary shocks, so a surprise in core can move a currency more than a surprise in headline.

Should beginners trade the CPI release?

Most beginners are better off staying out of the market for the release itself. Spreads widen, prices gap and stop orders can fill with slippage. If you want to trade CPI days, wait until conditions settle, size the position from a wider stop, and keep your risk per trade the same as on any other day.