What Is Inside the 3.4% Inflation Rate: Energy, Gasoline and a Calm Core

Headline inflation of 3.4 percent sounds like a broad price surge. The detail says it is a narrow one: a few categories that most households buy every week are doing nearly all the damage.

• August 2026 CPI rose 0.4 percent on the month and 3.4 percent over 12 months before seasonal adjustment ^[1].
• Core CPI, excluding food and energy, rose 0.3 percent on the month and 2.4 percent over the year ^[1].
• Energy was up 16.3 percent over 12 months and gasoline 27.4 percent, with gasoline up 3.9 percent in August alone ^[1].
• Shelter rose 3.0 percent and food 2.7 percent over 12 months ^[1].

The headline versus the core

The Bureau of Labor Statistics reported that the Consumer Price Index rose 0.4 percent in August on a seasonally adjusted basis, after 0.1 percent in July, and that the all-items index was up 3.4 percent over the previous 12 months before seasonal adjustment ^[1]. Remove food and energy and the picture changes: core CPI rose 0.3 percent in the month and 2.4 percent over the year ^[1]. A full percentage point separates the two measures.

Where the gap comes from

Energy explains it. The energy index rose 2.1 percent in August after falling 1.5 percent in July, and it is up 16.3 percent over 12 months. Within it, gasoline climbed 3.9 percent on the month and 27.4 percent from a year earlier ^[1]. That tracks the oil market: Brent crude closed at $101.21 on September 10, back above $100 for the first time since July, with the Strait of Hormuz still severely restricted ^[2].

What is steady

The big, sticky categories are less alarming. Shelter, the largest single component of the index, rose 0.3 percent in August and 3.0 percent over 12 months, and food rose 0.1 percent in the month and 2.7 percent over the year ^[1]. A central bank looks hard at those because they are slow to reverse.

The components, one by one

The BLS detail shows how uneven the year-over-year numbers were. Food at home rose 2.2 percent and food away from home 3.4 percent; electricity rose 3.8 percent and natural gas 4.4 percent, while fuel oil was up 52.0 percent ^[1]. Airline fares were up 23.4 percent over twelve months and 2.7 percent in August alone, apparel was up 3.6 percent, new vehicles 0.6 percent and medical care 1.6 percent, while used cars and trucks were down 2.3 percent ^[1].

The monthly increase came mostly from energy. BLS notes that the gasoline index rose 3.9 percent in August, accounting for over one third of the monthly all-items increase, and the energy index overall contributed 2.1 percent on the month; electricity (−0.2 percent) and natural gas (−1.1 percent) were lower on the month, and shelter rose 0.3 percent ^[1]. When one component accounts for a third of a monthly rise, the headline is telling you about that component more than about prices in general, which is the reason to read the core measure next to it.

Why the split matters

It determines what policy can do. Higher interest rates cool demand; they do not reopen a shipping lane. The Fed raised rates on September 16 while describing inflation as elevated ^[3], but if energy is the driver, the path of prices depends as much on geopolitics as on policy. For households, the practical effect is that the cost of getting to work has risen faster than the cost of nearly everything else.

Questions readers ask

What was inflation in August 2026?

CPI rose 3.4 percent over 12 months before seasonal adjustment, and core CPI rose 2.4 percent ^[1].

Why is headline inflation higher than core inflation?

Energy, up 16.3 percent over 12 months including gasoline up 27.4 percent, which core excludes ^[1].