Japan’s core CPI is the Consumer Price Index (CPI) for all items less fresh food. The commonly used core-core CPI is the CPI for all items less fresh food and energy. The difference is not a matter of one series being “more correct”: it tells you whether fresh food and energy are adding to or subtracting from the broader inflation reading.
For the latest national release, published on 18 September 2026, August’s year-on-year change was 1.7% for core CPI and 1.9% for the measure excluding fresh food and energy. In that month, the combined effect of the excluded fresh-food and energy components was therefore pulling the core measure down relative to core-core. That is a reading aid, not proof about any one item or a forecast for monetary policy.
Key takeaways
- Japan’s core CPI removes fresh food but retains energy; core-core removes both fresh food and energy.
- Read the two figures together. A higher core-core reading means the combined fresh-food-and-energy effect is lowering core CPI relative to the broader underlying-price measure; the reverse means it is raising it.
- Neither number is a complete measure of “underlying inflation.” The Bank of Japan (BOJ) also follows distribution-based indicators, wages, demand, import costs and expectations.
- The August 2026 release used the new 2025 CPI base. When comparing history, check the base and the exact series name rather than relying on a headline label.
The two Japan core CPI measures, side by side
The Statistics Bureau publishes national CPI for all items, all items less fresh food, and all items less fresh food and energy. The first exclusion removes fresh foods, whose prices can be unusually sensitive to weather. The second also removes energy, whose prices can move with overseas crude-oil markets.
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| Official series | Common English label | Excludes | What still remains | Best use |
|---|---|---|---|---|
| All items less fresh food | Core CPI | Fresh food | Energy and other food, goods and services | The Japanese CPI measure most often quoted in BOJ communications. |
| All items less fresh food and energy | Core-core CPI | Fresh food and energy | Other food, goods and services | A complementary read on broader price pressure after two volatile groups are removed. |
| All items less food (less alcoholic beverages) and energy | No single universal shorthand | Food except alcoholic beverages, plus energy | Non-food goods and services plus alcoholic beverages | A separate official reference series; do not substitute it for core-core CPI. |
The names matter. The Statistics Bureau notes that “core-core” can be used more loosely for indices excluding fresh food, energy or other groups. In this guide, it means the official all items less fresh food and energy series. That coverage check prevents a comparison with a different food-and-energy exclusion from being mistaken for the same measure.
What the latest release says—and what it does not
The official national CPI release for August 2026 was published on 18 September and reported the following year-on-year changes. The source has no English release page, so its title is translated here as National Consumer Price Index: August 2026.
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| August 2026 national CPI series | Index level, 2025 = 100 | Year-on-year change | Release date | Source |
|---|---|---|---|---|
| All items | 102.2 | 1.9% | 2026-09-18 | Statistics Bureau |
| All items less fresh food (core CPI) | 102.0 | 1.7% | 2026-09-18 | Statistics Bureau |
| All items less fresh food and energy (core-core CPI) | 102.5 | 1.9% | 2026-09-18 | Statistics Bureau |
The 0.2-percentage-point gap between the two exclusion series is a useful diagnostic: in August, fresh food plus energy made the core-CPI rate lower than the rate that excludes both. It does not identify the separate contribution of fresh food versus energy, and it does not say whether the gap will persist next month. For that, use the detailed CPI tables and the next monthly release rather than reverse-engineering more precision from two rounded annual rates.
The new 2025 base is also important. ATG’s CPI base-revision guide explains why a rebasing can change the weights and historical presentation used in an index. Keep the release’s base, date and series definition beside every comparison.
Why the BOJ watches more than one inflation measure
The BOJ says it pays particular attention to both official series. That is logical: fresh food and energy can create large, real changes in household purchasing power while also making it harder to judge whether price changes are broadening through the rest of the consumption basket.
But the BOJ does not treat core-core CPI as a one-number policy rule. Its price-assessment explainer lists additional research indicators: a trimmed mean, weighted median, mode and diffusion index of rising versus falling items. Those measures use the distribution of individual price changes; they are not simply another exclusion list.
The July 2026 Outlook Report highlights also separated near-term influences—crude oil, semiconductor prices linked to AI demand and yen depreciation—from the question of whether underlying inflation would move toward the 2% price-stability target. That makes a practical reading sequence more useful than choosing a single winner:
- Identify the exact CPI series and its year-on-year change.
- Compare core CPI with core-core CPI to see the combined fresh-food-and-energy effect.
- Check the BOJ’s broader indicators, wage evidence and the source of cost changes.
- Keep current data separate from the BOJ’s forecast and risk discussion.
For the market channel, this can be paired with ATG’s BOJ July 2026 outlook guide and Japan 10-year JGB yield explainer. Neither a CPI print nor a yield move, by itself, settles the policy outlook.
A compact checklist for using Japan CPI correctly
Before quoting a Japan inflation number, record the observation month, release date, base year, series label and comparison period. If the article says “core,” state whether it means all items less fresh food. If it says “core-core,” state whether it means all items less fresh food and energy.
Then separate three claims that are often blended together: the reported CPI observation, the likely effect of the excluded groups, and a view on underlying inflation or future policy. Only the first is established by the single release. The second needs detailed tables, and the third needs a broader evidence set.
This article is for informational purposes only and does not constitute investment advice.
Sources
- Statistics Bureau — Q&A about the Consumer Price Index
- Statistics Bureau — National Consumer Price Index: August 2026 (Japanese only; English title supplied)
- Bank of Japan — What are the factors on which the Bank bases its assessment of prices?
- Bank of Japan — Highlights of the Outlook for Economic Activity and Prices (July 2026)
