About the Heaviness of Smoking Index (HSI)
The Heaviness of Smoking Index (HSI) is a brief, widely used measure of nicotine dependence. Heatherton, Kozlowski, Frecker, Fagerstrom, and colleagues introduced it in 1989 as a short form of the six-item Fagerstrom Tolerance Questionnaire, keeping only the two items that carry most of the predictive value: how many cigarettes a person smokes per day, and how soon after waking they smoke their first one.
How the score is built
Both items are scored 0 to 3 points, and the two subscores are added for a total from 0 to 6:
- Cigarettes per day: 0 points for 10 or fewer, 1 point for 11-20, 2 points for 21-30, 3 points for 31 or more.
- Time to first cigarette after waking: 3 points for 5 minutes or less, 2 points for 6-30 minutes, 1 point for 31-60 minutes, 0 points for more than 60 minutes.
Interpreting the result
Higher totals indicate heavier nicotine dependence. Commonly used bands are 0-1 very low, 2-3 low to moderate, 4 moderate, and 5-6 high dependence. Time to first cigarette is often considered the single strongest indicator among the original questionnaire's items, since it reflects how quickly withdrawal symptoms drive smoking after a night without nicotine.
When to consult a professional
This tool performs the standard two-item HSI arithmetic for education and self-tracking. It is not a diagnosis and does not replace a clinical assessment. Anyone looking to reduce or quit smoking should talk with a healthcare provider about counseling, nicotine replacement therapy, and other evidence-based cessation support.