The UK publishes two headline inflation measures every month: CPI and CPIH. They usually move together but are rarely identical. The gap in August 2026 — 3.1% vs 3.3% — reflects a structural difference in what each measure covers.
What CPIH adds
CPIH includes owner-occupiers' housing costs (OOH), measured as an imputed rent — the amount a homeowner would theoretically pay to rent their own home. OOH has a weight of roughly 17% in the CPIH basket. When rental prices rise faster than the rest of the basket, CPIH runs above CPI, as in August.
In August 2026, private rental prices rose 7.8% in the year to August, according to the ONS's separate Index of Private Housing Rental Prices. That feeding into the OOH component is what drove the 0.2 percentage-point gap between CPIH and CPI.
Which measure to use — and when
The ONS designates CPIH as its preferred measure for overall consumer price inflation, arguing it better represents the full cost of housing for UK households. CPI is the UK's official inflation target measure under the Bank of England's mandate and is used in many public-sector wage agreements and regulated contracts (utilities, rail fares).
Neither measure includes mortgage interest payments directly. For households with large variable-rate mortgages — as many faced through 2023–24 — both CPI and CPIH significantly understate the actual financial burden. A separate "Household Costs Indices" series published by the ONS attempts to address this, though it is not yet widely used in policy.
In the context of August's data
The CPI release is covered in detail in our UK release note. The broader story — that energy drove both the UK and euro-area headlines higher while core stayed calm — is in our cross-country analysis. For the definitional background on headline vs core, see the glossary entries on headline inflation and core inflation.