The Heaviness of Smoking Index (HSI) is a fast, 2-item screen for nicotine dependence, built from just two everyday habits: how many cigarettes someone smokes per day, and how soon after waking they light the first one. Developed as a shortcut of the longer Fagerstrom Test for Nicotine Dependence, it is widely used in research and smoking-cessation programs whenever a quick, low-burden measure is needed. This article explains how the score is built, how to read it, and where it fits alongside the full Fagerstrom test.

How the HSI works

Two items are each graded 0 to 3 points and summed to a total of 0 to 6. Cigarettes per day scores intuitively — more cigarettes, more points. Time to first cigarette after waking runs the other way: the sooner someone smokes after waking, the more points it scores, because a short time-to-first-cigarette is one of the strongest self-report markers of physical nicotine dependence.

The two items were chosen because, among all six items on the full Fagerstrom Test for Nicotine Dependence (FTND), they correlate most strongly with biochemical measures of nicotine intake such as cotinine levels. That makes the HSI a reasonable stand-in for the full test when speed matters more than precision.

Reading the score and dependence tier

A total of 0 to 2 is generally read as low dependence, 3 to 4 as moderate, and 5 to 6 as high. Higher scores are associated with more pronounced withdrawal symptoms when quitting and, in research settings, with a lower likelihood of success on a first quit attempt without support.

The HSI is a screening tool, not a diagnosis. It is commonly used to flag who might benefit most from structured cessation support — counseling, nicotine replacement therapy, or medication — rather than to make a clinical determination on its own.

Limits and how it should be used

Because the HSI only uses two of the six FTND items, it necessarily loses some of the nuance the full test captures — for example, difficulty refraining from smoking in restricted places, or smoking when ill. For a fuller picture, see the full 6-item Fagerstrom test.

This calculator is for informational and educational purposes only. It is not a diagnosis and does not replace an assessment by a healthcare provider. Anyone considering quitting, especially a heavy or long-time smoker, should talk to a healthcare provider about cessation support and treatment options.