Heavy naphtha is a distillation cut comprised material of roughly the same density as finished gasoline. Heavy naphtha molecules typically have from 7-9 carbon atoms. Its boiling range can be from 180F to 330F.

The heavy naphtha distillation cut has is primarily sent to the reformer to upgrade its quality to make it suitable as a gasoline blend stock. Heavy naphtha can be blended directly into gasoline, but its low octane makes this undesirable.

Refiners can adjust the cut points of heavy naphtha to shift volume into light naphtha and/or kerosene, and to reduce the volume going to the reformer. Shifting the heavier end of the heavy naphtha into kerosene allows a refiner to increase kerosene and diesel yield, but at the cost of lowering the flash point of the kerosene.