HSI Calculator - Heaviness of Smoking Index
The Heaviness of Smoking Index (HSI) measures nicotine dependence using just two questions: how soon you smoke after waking and how many cigarettes you smoke each day. Answer both questions and the calculator gives you a score from 0 to 6 with a low, medium, or high dependence rating, a breakdown of each question score, an annual cost estimate, and a plain-English explanation of what your score means for quitting.
Formula
Worked example
A person who smokes their first cigarette 6 to 30 minutes after waking (2 points) and smokes 15 cigarettes per day (1 point) has an HSI of 2 + 1 = 3, placing them in the medium dependence band.
What is the Heaviness of Smoking Index?
The Heaviness of Smoking Index (HSI) is a brief two-item questionnaire developed by Kozlowski et al. to measure nicotine dependence in daily smokers. It distils the two most predictive items from the full Fagerstrom Test for Cigarette Dependence into a single score from 0 to 6. The two questions are how soon after waking a person smokes their first cigarette (the strongest individual predictor of dependence) and how many cigarettes they smoke per day. Because it takes under a minute to complete and needs no equipment, the HSI is widely used in both clinical settings and large population surveys.
How the scoring works
Each question is scored on a 0-to-3 scale and the two scores are added together. For time to first cigarette: within 5 minutes earns 3 points, 6 to 30 minutes earns 2 points, 31 to 60 minutes earns 1 point, and more than 60 minutes earns 0 points. For daily cigarette count: 10 or fewer earns 0 points, 11 to 20 earns 1 point, 21 to 30 earns 2 points, and 31 or more earns 3 points. The total ranges from 0 (no measurable physiological dependence) to 6 (very high dependence). Scores of 0 to 1 indicate low dependence, 2 to 4 indicate medium dependence, and 5 to 6 indicate high dependence.
Why time to first cigarette matters most
Of the two HSI questions, time to first cigarette after waking is the stronger predictor of nicotine dependence and withdrawal severity. When a person sleeps, blood nicotine falls to near zero over six to eight hours. A smoker who reaches for a cigarette within five minutes of waking is effectively treating acute withdrawal as the very first act of the day. Research consistently shows that early-morning smokers experience more severe withdrawal symptoms, have lower quit rates on their own, and respond better to pharmacological cessation aids such as varenicline or nicotine patches. Someone who can wait an hour or more has more time before craving becomes urgent and is typically less physiologically dependent.
HSI versus the full Fagerstrom Test
The Fagerstrom Test for Cigarette Dependence (FTCD) contains six questions and scores from 0 to 10. The HSI uses only the two most predictive FTCD items, making it faster to complete while retaining much of the same information. A large study in cancer patients found that the HSI and the FTCD showed substantial agreement (Cohen kappa approximately 0.70) and nearly identical predictive accuracy for cessation outcomes. For busy clinical environments, the HSI offers a practical alternative to the full FTCD without a significant loss of clinical utility. One known limitation is a floor effect in lighter smokers (fewer than 10 cigarettes per day), where the score may understate dependence relative to other measures.
Using your score to choose a quitting approach
A low HSI (0 to 1) suggests behavioral intervention alone may be enough: setting a firm quit date, identifying triggers, and using telephone or app-based support. A medium HSI (2 to 4) typically benefits from nicotine replacement therapy combined with behavioral support; combining both roughly doubles success rates compared with willpower alone. A high HSI (5 to 6) is associated with stronger physical dependence and more severe withdrawal, and prescription medications such as varenicline (Champix or Chantix) or bupropion, combined with structured counseling, offer the best cessation rates in this group. Whatever your score, repeated quit attempts are normal: most people who successfully quit do so after multiple serious attempts, each of which builds practical coping skills.
HSI score interpretation
| HSI Score | Dependence Level | Typical cessation approach |
|---|---|---|
| 0-1 | Low | Behavioral support; NRT optional |
| 2-4 | Medium | NRT (patch, gum or lozenge) + counseling |
| 5-6 | High | Prescription medication + structured counseling |
Dependence bands validated in clinical and population survey research. The HSI correlates well with the longer Fagerstrom Test for Cigarette Dependence (FTCD).
Frequently asked questions
What is a good HSI score?
A lower score indicates less physical dependence on nicotine. Scores of 0 to 1 are classified as low dependence, 2 to 4 as medium, and 5 to 6 as high. There is no universally "good" score for a current smoker - the result is a tool to choose the right support for quitting, not a judgment.
Is the HSI the same as the Fagerstrom test?
No, but they are closely related. The Fagerstrom Test for Cigarette Dependence (FTCD) has six questions and scores from 0 to 10. The HSI uses only the two most predictive FTCD items, giving a score from 0 to 6. Research shows the two scales agree closely and predict cessation outcomes with similar accuracy, so the HSI is often preferred where brevity matters.
Can the HSI be used for e-cigarettes or other tobacco products?
The HSI was developed and validated specifically for cigarette smoking. While the two questions could in principle be applied to other nicotine products, the scoring bands and clinical interpretation guidelines are based on cigarette research. For e-cigarettes or smokeless tobacco, different validated scales exist.
What does it mean if I smoke my first cigarette within 5 minutes of waking?
Smoking within 5 minutes of waking earns the maximum 3 points for that question and is the single strongest behavioral indicator of high nicotine dependence. It reflects severe early-morning withdrawal and typically predicts more difficult quitting and stronger benefit from pharmacological aids such as varenicline or a nicotine patch.
How accurate is the HSI at predicting whether I can quit?
The HSI has modest predictive power for cessation outcomes - large clinical studies report areas under the ROC curve of around 0.60, meaning it is better than chance but far from a definitive predictor. A higher score means quitting will likely be harder and more structured support will help, but many people with high scores do successfully quit, often with professional support and multiple attempts.
Should I use the HSI result to talk to my doctor?
Yes. The HSI was designed partly as a clinical communication tool. Sharing your score with a doctor or pharmacist helps them quickly gauge your level of dependence and recommend an appropriate combination of behavioral support, nicotine replacement, or prescription medication. You do not need to memorize the interpretation - the score itself is enough to start the conversation.
Sources
- Kozlowski LT et al. - Comparing tobacco cigarette dependence with other drug dependencies: nicotine and TTFC as the principal markers of the heaviness of smoking index (HSI). JAMA, 1994.
- Comparing the Fagerstrom Test and Heaviness of Smoking Index in predicting smoking abstinence in cancer patients - PubMed Central, 2024.