Consumer price inflation, updating weights: 2026

• The weights for the Consumer Prices Index including owner occupiers’ housing costs (CPIH) and the Consumer Prices Index (CPI) have been updated to reflect changes in household spending patterns.

Consumer price inflation is an important indicator of how the UK economy is performing. We review and update the "shopping baskets" of items and their economic importance (typically referred to as "weights") each year. These items are used to compile the various measures of consumer price inflation to ensure the indices are representative of the latest consumer spending patterns. This article focuses on the latest updates and changes to the weights applied within these baskets.

We use a classification structure to calculate the Consumer Prices Index including owner occupiers' housing costs (CPIH) and Consumer Prices Index (CPI), as explained in Section 3: Construction of UK consumer price indices of our CPI technical manual: 2026. Historically, the weights were rounded to integers as parts per thousand of the all-items index at the class level. This class level is defined as the four-digit classification of individual consumption by purpose (COICOP) level. Subclass level weights, which are defined as the five-digit COICOP level (COICOP5), are then rescaled to reflect this rounding. This integer rounding was removed from the calculation process from the 2024 weights update. For presentational purposes, weights will be displayed to two decimal places in this article, unless otherwise specified. This change does not apply to the Retail Prices Index (RPI) weights.

This article will mainly focus on CPIH. Further detail on the methods discussed in this article can be found in:

• our CPIH compendium

• our CPI technical manual: 2026

• our more detailed Consumer price inflation, updating weights: 2021 article

Explanation of weights

Consumer price inflation is the rate at which the prices of goods and services rise or fall; it is estimated using price indices. One way to understand a price index is to think of a large "shopping basket" that contains goods and services that are typically bought by all households. The price index estimates changes to the total cost of this basket by calculating the average of price changes of the items within the basket.

Households spend more on some goods and services than others. For example, a 10% increase in the price of petrol will have a much bigger impact on the basket than a similar rise in the price of tea. For this reason, the components of price indices are weighted using the amount we spend on these items. This ensures that the price index reflects the relative importance of the various items in the average shopping basket.

The various weights used in the calculation of consumer price inflation and the items that form the shopping basket are reviewed and updated each year. This ensures weights are representative of overall household expenditure patterns (but not any one specific household) and that they reflect the introduction of new items and removal of old items, as explained in our Measuring the changing prices and costs faced by households blog post. We explain the annual update to the contents of the shopping basket in our Consumer price inflation basket of goods and services article.

Weight changes between 2025 and 2026

Our consumer price inflation weights reflect the best available understanding of what households spent their money on at the time the weights were produced. Indices are not revised historically, as set out in our Revisions and corrections of errors policies. Source data are often revised at a later date. However, these revisions are not factored into the calculation of weights, so only the latest year's data are used in each weights update. This means that the changes in weights between years may reflect changes in data sources, methods, definitions, and changes in spending patterns.

We introduced improvements that affect the current set of weights, as described in the Blue Book 2025. For this reason, the weights should not be used to analyse trends in consumer spending over time. This weights update is our best estimate of current consumer spending, so they will not be revised.

There are two separate updates to 2026 weights, which is in line with our "double update" methodology introduced in 2017. These are:

• the first update of weights for the January 2026 set of indices, where expenditure for 2024 is price updated to December 2025 (see Section 5: Data sources and quality for further details on price updating)

• the second update of weights for the February to December 2026 indices, where the expenditure for 2024 is price updated to January 2026

Typically, changes in weight between years can be caused by two main factors:

• a change in the underlying expenditure used to calculate the weight

• a change in the price factor applied to price update the expenditure (this method applies price change to the expenditure to align it with the price reference period; see Section 5: Data sources and quality for more details)

The change resulting from comparing the February 2026 weights update with the January 2026 weights update is mainly owing to any notable movement in price update factor. This is effectively caused by price changes between December and January. Any change resulting from comparing January 2026 updated weights with last year's weights are because of a combination of changes in expenditure (comparing underlying expenditure used in this update with the expenditure used last year) and any notable movement in the price update factor. Weights are relative, so any change in weight caused by these factors will cause a relative reallocation of weight elsewhere in the basket.

Table 1 shows the Consumer Prices Index including owner occupiers' housing costs (CPIH) divisional-level classification of individual consumption by purpose (COICOP) weights. Table 2 shows the Consumer Prices Index (CPI) divisional-level COICOP weights. The most notable movements are explained briefly in the Notable 2026 weight changes subsection within this section. This analysis mainly focuses on the CPIH, though the same reasoning will also underpin movements in CPI weights.

More detailed weights for CPIH, CPI and Retail Price Index (RPI) are available in our accompanying dataset.

Notable 2026 weight changes

Division 4: Housing, water, electricity, gas and other fuels

Division 4 has seen an increase in weight of 10.70 parts per thousand (ppt), when comparing the January 2026 weight with the weight used for February to December 2025.

This increase is driven by a 9.79 ppt increase in the COICOP5 for owner occupiers' housing costs, because of an increase in underlying expenditure used in the latest weights update. Actual rentals for housing have also seen an increase in weight, but at a smaller magnitude of 0.86 ppt in the CPIH and 2.15 ppt in the CPI.

There are smaller upward effects from other areas of the basket within Division 4, such as water supply and sewerage.

These increases are offset by the COICOP5 for natural gas and town gas, where the weight fell by 2.04 ppt. This is caused by a large fall of over 30% in the underlying expenditure used in the latest weights update, compared with the expenditure used last year.

Division 7: Transport

Division 7 increased in weight by 6.94 ppt, when comparing the January 2026 weight with the weight used for February to December 2025. The largest contribution to the increase came from the class for maintenance and repairs, which increased by 2.67 ppt. This was driven by an increase in underlying expenditure used in this year's weights. The COICOP5 for second hand cars increased by 1.95 ppt. This was largely driven by an increase in the price update factor of 8.6% used in this year's weights.

The class for passenger transport by air increased in weight by 1.53 ppt in the January 2026 update of weights, which is driven by a price effect. The price update ratio used at the first update of weights is usually high, which is in line with the seasonal increase in air travel prices in the December CPI. As expected, the weight for this COICOP5 then falls back by 1.47 ppt at the second weights update, which is driven by the subsequent fall in price of air fares between the December and January CPI.

For reference, the latest updated weight for passenger transport by air of 4.14 ppt in February 2026 is slightly higher than the second update of weight of 4.09 ppt in 2025.

Division 12: Miscellaneous goods and services

Division 12 has seen a fall in weight of 5.43 ppt, when comparing the January 2026 weight with last year.

The COICOP5 for articles for personal hygiene and wellness fell by 2.11 ppt in the January 2026 weights update. The fall is driven by lower expenditure for this category being used in the latest weights update. This was mainly driven by revisions that have come through in the Blue Book 2025.

The COICOP5 for childcare services fell by 2.12 ppt. There has been a large downward revision to the expenditure for this area of the basket in the latest Blue Book, which is causing the subsequent fall in 2026 weight.

The update of consumer price inflation weights is mainly based on national accounts household final consumption expenditure (HHFCE) data at a two-year lag. In normal times, these data are deemed to be representative of household spending patterns of the calendar year "t-1", which is the calendar year before the weights take effect. This means for the latest set of consumer inflation weights, we are using 2024 expenditure (known as the weights reference period). This is consistent with the latest UK National Accounts, which are the most complete and comprehensive set of household spending data available to us. More detail is available in Section 8: Weights of our Consumer Price Indices (CPI) technical manual: 2026.

Once we have our expenditure data, we then apply a process known as "price updating". We apply this price update process for methodological reasons. The Consumer Prices Index including owner occupiers' housing costs (CPIH) and the CPI are Laspeyres-type price indices, or more specifically, Lowe price indices (for more details, see Section 3.3: Index calculation of our CPI technical manual: 2026. To achieve a Lowe price index, the period which our expenditure data represent (the weights reference period) should be the same as the period to which we compare our monthly prices (the price reference period). Whatever source is used for expenditure weights, given the delays in collecting and processing this data, the weight reference period will always predate the price reference period, given that CPIH and CPI use a "double update" methodology, introduced in 2017.

Expenditure is adjusted for any price change over the interval between the weights reference period and the price reference period to align it with the price reference period. In other words, the expenditure is revalued at price reference period prices to fall in line with a Laspeyres-type methodology. For 2026 CPI and CPIH weights, this means we apply a factor to the underlying expenditure based on the change in price between December 2025 and the average of 2024 for the initial weights update. The second update moves the price change to reference January 2026 prices. This price updating is applied at the lowest five-digit classification of individual consumption by purpose (COICOP) level. Our approach is consistent with the Harmonised Index of Consumer Prices (PDF, 10.6MB), which underpinned the development of the CPI.

Therefore, any substantial change in price between weights updates will most likely lead to a subsequent change in weight.

The Classification of Individual Consumption According to Purpose (COICOP) underpins some of the main statistics that we produce. The classification was updated in 2018 to reflect changes in household expenditure patterns since the late 1990s, as described in the United Nations COICOP 2018 report (PDF, 1.2MB).

The UK currently uses the version of COICOP that was introduced in 1999 and updated in 2017, as described in our Assessing the impact of methodological improvements on the Consumer Prices Index methodology. The update added additional detail at the subclass level.

We plan to implement the updated COICOP 2018 by 2029, as referenced in Annex B4: Prices of our The plan for Office for National Statistics's (ONS's) economic statistics and our subsequent ONS plan for economic statistics: progress update December 2025. We will also consider re-referencing the CPI as part of the move to the new classification and will provide users with full details of our plans once they are finalised.