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Quick answer
Pack-years = cigarettes per day ÷ 20 × years smoked. 1 pack a day for 20 years = 20 pack-years; ½ pack for 40 years = 20; 10 a day for 20 years = 10; 20 a day for 30 years = 30. In the U.S., 20+ pack-years at age 50–80 qualifies for a yearly low-dose CT lung scan if you smoke or quit within 15 years (USPSTF 2021).
Add each period you smoked a different amount, including roll-ups, rolling tobacco, cigars, pipe and bidis. The calculator totals your pack-year history, estimates lifetime cigarettes, and checks eligibility against five screening guidelines.
Last updated: · Sources: USPSTF 2021, ACS 2023, CMS NCD 210.14, NHS England, G-BA 2025. Guides: how to calculate pack-years · screening thresholds
Smoking history
cigarettes per day · 1 unit = 1 cigarette
Pack-years
25
20 to under 30 pack-years
Average
20 cig/day
over 25 years
Lifetime total
≈ 182,500
cigarettes (equivalent)
Meets the 20 pack-year threshold for yearly low-dose CT lung screening (USPSTF 2021, ACS 2023, Medicare 2022) — age and quit rules also apply.
Lung cancer screening check
USPSTF 2021: meets criteria
Meets age, pack-year and quit criteria. Yearly low-dose CT. Stop once 15 years have passed since quitting or if health limits life expectancy or surgery.
American Cancer Society 2023: meets criteria
Meets age, pack-year and quit criteria. Dropped the 15-year quit limit in 2023. Not for people with serious conditions that limit life expectancy.
Medicare (CMS NCD 210.14, 2022): meets criteria
Meets age, pack-year and quit criteria. No symptoms of lung cancer, a written order, and a shared decision-making visit before the first scan.
Germany (G-BA / LuKrFrühErkV, from April 2026): meets criteria
Meets age, pack-year, duration and quit criteria. Statutory health insurance benefit since 1 April 2026; low-dose CT every 12 months after a GP or internist confirms eligibility.
NHS England Lung Cancer Screening: risk check
Eligible for a lung health check; a risk score decides whether you are offered a CT scan.
Germany also needs 25+ years of smoking; years are added from your cigarette periods, so enter periods one after another.
Education only — not a diagnosis or a screening order. Talk with your doctor about screening and quitting. Free help in the U.S.: 1-800-QUIT-NOW.
Common smoking histories, calculated with the formula above.
20 cigarettes a day for 30 years
30 pack-years
≈ 219,000 cigarettes
½ pack a day for 40 years
20 pack-years
≈ 146,000 cigarettes
½ pack a day for 33 years
16.5 pack-years
≈ 120,450 cigarettes
15 cigarettes a day for 8 years
6 pack-years
≈ 43,800 cigarettes
10 cigarettes a day for 20 years
10 pack-years
≈ 73,000 cigarettes
2 packs a day for 25 years
50 pack-years
≈ 365,000 cigarettes
1 pack/day for 10 years, then 10/day for 15 years
17.5 pack-years
≈ 127,750 cigarettes
50 g of rolling tobacco a week for 20 years
14.29 pack-years
≈ 104,286 cigarettes
2 large cigars a day for 15 years
6 pack-years
≈ 43,800 cigarettes (equivalent) · not counted for screening
Find your cigarettes per day on the left and years smoked across the top. Shaded cells reach 20 pack-years, the U.S. screening threshold.
| Cigarettes / day | 5 yr | 10 yr | 15 yr | 20 yr | 25 yr | 30 yr | 35 yr | 40 yr | 50 yr |
|---|---|---|---|---|---|---|---|---|---|
| 5 (0.25 pack) | 1.25 | 2.5 | 3.75 | 5 | 6.25 | 7.5 | 8.75 | 10 | 12.5 |
| 10 (0.5 pack) | 2.5 | 5 | 7.5 | 10 | 12.5 | 15 | 17.5 | 20 | 25 |
| 15 (0.75 pack) | 3.75 | 7.5 | 11.25 | 15 | 18.75 | 22.5 | 26.25 | 30 | 37.5 |
| 20 (1 pack) | 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 50 |
| 25 (1.25 pack) | 6.25 | 12.5 | 18.75 | 25 | 31.25 | 37.5 | 43.75 | 50 | 62.5 |
| 30 (1.5 pack) | 7.5 | 15 | 22.5 | 30 | 37.5 | 45 | 52.5 | 60 | 75 |
| 40 (2 pack) | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 100 |
15 is the German screening minimum, 20 is the U.S. threshold, and 30 was the U.S. threshold before 2021.
| Cigarettes / day | Years to 15 | Years to 20 | Years to 30 |
|---|---|---|---|
| 5 | 60 | 80 | 120 |
| 10 | 30 | 40 | 60 |
| 15 | 20 | 26.67 | 40 |
| 20 | 15 | 20 | 30 |
| 30 | 10 | 13.33 | 20 |
| 40 | 7.5 | 10 | 15 |
Low-dose CT (LDCT) screening is offered yearly to people at high risk. In the U.S. you need 20+ pack-years and an age of 50–80; Germany uses 15+ pack-years and 25+ years of smoking; England uses a risk score instead of a pack-year cutoff. All of them count cigarette smoking.
| Guideline | Age | Pack-years | If you quit | Notes |
|---|---|---|---|---|
| USPSTF 2021 | 50–80 | 20+ | Currently smoke or quit within the past 15 years | Yearly low-dose CT. Stop once 15 years have passed since quitting or if health limits life expectancy or surgery. |
| American Cancer Society 2023 | 50–80 | 20+ | Current or former smokers — years since quitting does not matter | Dropped the 15-year quit limit in 2023. Not for people with serious conditions that limit life expectancy. |
| Medicare (CMS NCD 210.14, 2022) | 50–77 | 20+ | Currently smoke or quit within the past 15 years | No symptoms of lung cancer, a written order, and a shared decision-making visit before the first scan. |
| Germany (G-BA / LuKrFrühErkV, from April 2026) | 50–75 | 15+ (and 25+ years smoking) | Currently smoke or quit less than 10 years ago | Statutory health insurance benefit since 1 April 2026; low-dose CT every 12 months after a GP or internist confirms eligibility. |
| NHS England Lung Cancer Screening | 55–74 | No pack-year cutoff | Anyone who has ever smoked | Invited via your GP for a lung health check. A risk score (PLCOm2012 ≥1.51% or LLPv2 ≥2.5%) decides who gets a low-dose CT scan. |
Before 2021, USPSTF and Medicare required 30 pack-years and a starting age of 55 — the criteria from the National Lung Screening Trial. If you were told you didn't qualify years ago, check again.
Approximate cigarette equivalents used in UK clinical practice. They are estimates — product sizes vary.
| Product | Equals | Example × 10 years |
|---|---|---|
| Hand-rolled cigarettes (roll-ups) | 1 cigarette | 10 roll-ups per day → 5 pack-years |
| Loose rolling tobacco | 1 g = 2 cigarettes (25 g pouch ≈ 50) | 50 grams per week → 7.14 pack-years |
| Bidis (beedis)not counted for screening | 0.5 cigarette | 20 bidis per day → 5 pack-years |
| Small cigars (e.g. Café Crème)not counted for screening | 1.5 cigarettes | 5 small cigars per day → 3.75 pack-years |
| Cigarillos / medium cigarsnot counted for screening | 2 cigarettes | 5 cigarillos per day → 5 pack-years |
| Large cigarsnot counted for screening | 4 cigarettes | 2 cigars per day → 4 pack-years |
| Pipe (bowls)not counted for screening | 2.5 cigarettes | 4 pipe bowls per day → 5 pack-years |
Bands are based on screening thresholds, not a personal risk estimate. There is no safe amount of smoking.
| Pack-years | What it means |
|---|---|
| Under 10 pack-years | Below every screening threshold. There is still no safe level: even light smoking raises the risk of lung cancer, COPD, heart attack and stroke. |
| 10 to under 15 pack-years | Below the screening thresholds in the U.S. (20) and Germany (15). Quitting now gives the largest benefit. |
| 15 to under 20 pack-years | Meets Germany’s 15 pack-year minimum (with 25+ years of smoking). Below the 20 pack-year threshold used by USPSTF, ACS and Medicare. |
| 20 to under 30 pack-years | Meets the 20 pack-year threshold for yearly low-dose CT lung screening (USPSTF 2021, ACS 2023, Medicare 2022) — age and quit rules also apply. |
| 30+ pack-years | Above the older 30 pack-year cutoff used by the NLST trial, USPSTF 2013 and Medicare before 2022. Heavy cumulative exposure — screening and quitting both matter. |
Your pack-years don't go down, but your risk does. Timeline from the CDC, compared with continuing to smoke.
| After quitting | Change |
|---|---|
| 1–12 months | Coughing and shortness of breath decrease. |
| 1–2 years | Risk of heart attack drops sharply. |
| 3–6 years | Added risk of coronary heart disease drops by half. |
| 5–10 years | Added risk of mouth, throat and voice-box cancer drops by half; stroke risk decreases. |
| 10–15 years | Added risk of lung cancer drops by half. |
| 15 years | Risk of coronary heart disease is close to that of someone who never smoked. |
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