The science
Every claim in the calculator is sourced.
What follows is the framework we use to look at a life — seven domains we measure and map — followed by the citation library behind every behavioral factor. Each cited source is verified at build time; if a URL stops resolving or a title shifts, the build fails before shipping.
The framework
The shape of your life, across seven domains.
The headline number is useful, but it’s a single dimension. Real life isn’t one dimension. So alongside the number, we render your answers as a “risk map” — your shape across seven domains that consistently show up in longevity research.
The map is built around two overlaid shapes. The smaller, dashed shape is where you are now. The larger, filled shape is where you could be if you committed to the changes you’re willing to commit to. The visual gap between them is your headroom — and most of the time, it’s lopsided. Strong in some domains, weak in others. That’s the point.
Sample shape, not based on any specific user. Yours fills in when you take the calculator.
Movement
Weekly activity, and how much you sit on a typical day.
Reaching 150 active minutes a week captures most of the longevity benefit of exercise. Long sitting matters mainly for people who are otherwise inactive — enough daily movement offsets it.
Sleep
Average nightly sleep.
Each hour below about seven a night is associated with higher mortality. Long sleep is too, but that link likely reflects underlying illness, so we don't penalize it.
Nutrition
Diet quality, from home-cooked-and-vegetable-heavy down to mostly processed.
The best-scoring diets are associated with about a fifth lower mortality than the worst. The target here is reasonable, not perfectionist.
Connection
How connected you are to other people.
Social isolation and loneliness are both associated with higher mortality, though untangling cause from effect is hard.
Body
Height and weight (BMI), or your waist compared with your height (the optional string test).
Higher BMI is linked to higher mortality, but BMI can't tell muscle from fat — so the string test, which tracks the fat that matters, replaces it when you take it. Being active offsets much of the risk of carrying extra weight.
Substances
Smoking, vaping and alcohol.
Smoking remains the single largest lifestyle factor in longevity research. Alcohol is the area where consensus has shifted most in the last decade.
Prevention
Whether you know your blood pressure, and whether it's controlled.
High blood pressure is one of the world's leading risks for early death and usually has no symptoms. Lowering it is backed by randomized trials.
Each axis is scaled to its own range, so the shape shows balance, not size: a half-full Sleep axis usually means far fewer years than a half-full Substances axis. The numbers below give the actual stakes.
The factors
Factor
Smoking
Current smokers have a life expectancy more than a decade shorter than people who have not smoked, and quitting before age 40 is associated with avoiding about 90% of that excess risk. Smoking even less than one cigarette a day is associated with a 64% higher risk of death. Vaping has not been studied long enough to measure its effect on lifespan.
Years at stake
~10.5 years between the best and worst answer
For a 40-year-old in the US with otherwise typical habits. Smaller at older ages.
Strength of evidence
Strong
Declared as “associated with” — we don’t say “causes” unless the evidence supports it.
Sources
21st-century hazards of smoking and benefits of cessation in the United States.
New England Journal of Medicine (NEJM), 2013·PubMed 23343063
Association of Long-term, Low-Intensity Smoking With All-Cause and Cause-Specific Mortality in the National Institutes of Health-AARP Diet and Health Study.
JAMA Internal Medicine, 2017·PubMed 27918784
The public health consequences of e-cigarettes: a review by the National Academies of Sciences. A call for more research, a need for regulatory action.
Addiction, 2019·PubMed 30347473
Tobacco
WHO·who.int
Limitations
The vaping estimate is provisional: long-term mortality data for e-cigarettes do not exist yet. More broadly, the research here describes population-level patterns; individual outcomes vary widely based on factors this calculator doesn’t capture. For your specific situation, consult a healthcare professional.
Factor
Alcohol
Low-volume drinking is not associated with lower mortality than lifelong abstinence. Risk of death rises at higher intake, starting around 25 g of alcohol a day for women (under two US drinks) and 45 g for men (about three drinks).
Years at stake
~2.3 years between the best and worst answer
For a 40-year-old in the US with otherwise typical habits. Smaller at older ages.
Strength of evidence
Moderate
Declared as “associated with” — we don’t say “causes” unless the evidence supports it.
Sources
Limitations
Observational data. Older studies that counted former heavy drinkers as abstainers made light drinking look protective; the meta-analysis used here corrects for that. More broadly, the research here describes population-level patterns; individual outcomes vary widely based on factors this calculator doesn’t capture. For your specific situation, consult a healthcare professional.
Factor
Physical activity
Compared with no leisure-time activity, reaching the guideline minimum of 150 minutes of moderate activity a week is associated with about 31% lower mortality risk — nearly the full longevity benefit of exercise. Activity below the minimum is still associated with about 20% lower risk.
Years at stake
~4.3 years between the best and worst answer
For a 40-year-old in the US with otherwise typical habits. Smaller at older ages.
Strength of evidence
Moderate
Declared as “associated with” — we don’t say “causes” unless the evidence supports it.
Sources
Limitations
Observational data. People who are already ill tend to exercise less, which can exaggerate the benefit. More broadly, the research here describes population-level patterns; individual outcomes vary widely based on factors this calculator doesn’t capture. For your specific situation, consult a healthcare professional.
Factor
Sitting time
Among the least active people, sitting more than 8 hours a day is associated with higher mortality. About 60–75 minutes of moderate activity a day appears to offset that association.
Years at stake
~1.5 years between the best and worst answer
For a 40-year-old in the US with otherwise typical habits. Smaller at older ages.
Strength of evidence
Moderate
Declared as “associated with” — we don’t say “causes” unless the evidence supports it.
Limitations
Sitting time is self-reported, and the 4–7 hour band is interpolated between the published bands. More broadly, the research here describes population-level patterns; individual outcomes vary widely based on factors this calculator doesn’t capture. For your specific situation, consult a healthcare professional.
Factor
Sleep
Sleeping less than about 7 hours a night is associated with a 6% higher mortality risk for each hour of shortfall. Long sleep is also associated with higher risk, but that link is widely attributed to underlying illness, so this calculator does not penalize it.
Years at stake
~1.0 years between the best and worst answer
For a 40-year-old in the US with otherwise typical habits. Smaller at older ages.
Strength of evidence
Moderate
Declared as “associated with” — we don’t say “causes” unless the evidence supports it.
Limitations
Self-reported sleep. Long sleep is left unscored because its link to mortality is likely driven by illness. More broadly, the research here describes population-level patterns; individual outcomes vary widely based on factors this calculator doesn’t capture. For your specific situation, consult a healthcare professional.
Factor
Body size (BMI or the string test)
Compared with a BMI of 22.5–25, a BMI of 30–35 is associated with about 45% higher all-cause mortality, and 35–40 with 94% higher. BMI also counts muscle, so the optional string test measures waist-to-height instead: each 0.1 increase is associated with 24% higher mortality, even after accounting for BMI. Fitness offsets much of the risk — fit people carrying extra weight had mortality similar to fit people at a healthy weight.
Years at stake
~5.1 years between the best and worst answer
For a 40-year-old in the US with otherwise typical habits. Smaller at older ages.
Strength of evidence
Moderate
Declared as “associated with” — we don’t say “causes” unless the evidence supports it.
Sources
Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents.
The Lancet, 2016·PubMed 27423262
Central fatness and risk of all cause mortality: systematic review and dose-response meta-analysis of 72 prospective cohort studies.
BMJ, 2020·PubMed 32967840
Fitness vs. fatness on all-cause mortality: a meta-analysis.
Progress in Cardiovascular Diseases, 2014·PubMed 24438729
Limitations
BMI can't tell muscle from fat, so muscular people can look riskier than they are — the optional string test fixes that, though it places you in a band rather than measuring exactly. A low BMI isn't scored. How much activity offsets the risk is our estimate: the study measured fitness on a treadmill, while we use your self-reported activity, so we let it cancel at most half the effect. More broadly, the research here describes population-level patterns; individual outcomes vary widely based on factors this calculator doesn’t capture. For your specific situation, consult a healthcare professional.
Factor
Diet quality
Diets scoring highest on established diet-quality indexes (HEI, AHEI, DASH) are associated with about 22% lower all-cause mortality than the lowest-scoring diets.
Years at stake
~1.7 years between the best and worst answer
For a 40-year-old in the US with otherwise typical habits. Smaller at older ages.
Strength of evidence
Moderate
Declared as “associated with” — we don’t say “causes” unless the evidence supports it.
Sources
Diet Quality as Assessed by the Healthy Eating Index, Alternate Healthy Eating Index, Dietary Approaches to Stop Hypertension Score, and Health Outcomes: An Updated Systematic Review and Meta-Analysis of Cohort Studies.
Journal of the Academy of Nutrition and Dietetics, 2018·PubMed 29111090
Healthy diet
WHO·who.int
Limitations
A single self-rating is mapped onto research diet-quality quintiles; most people rate their diet more favorably than a detailed survey would. More broadly, the research here describes population-level patterns; individual outcomes vary widely based on factors this calculator doesn’t capture. For your specific situation, consult a healthcare professional.
Factor
Blood pressure
High blood pressure often has no symptoms — a reading is the only way to know. In randomized trials, every 10 mmHg reduction in systolic blood pressure reduced all-cause mortality by 13%.
Years at stake
~1.7 years between the best and worst answer
For a 40-year-old in the US with otherwise typical habits. Smaller at older ages.
Strength of evidence
Strong
Declared as “reduces” — we don’t say “causes” unless the evidence supports it.
Sources
Blood pressure lowering for prevention of cardiovascular disease and death: a systematic review and meta-analysis.
The Lancet, 2016·PubMed 26724178
Hypertension
WHO·who.int
“WHO: People with high blood pressure may not feel symptoms. The only way to know is to get your blood pressure checked. An estimated 600 million adults with hypertension (44%) are unaware that they have the condition.”
Limitations
Trial evidence covers lowering blood pressure with treatment. The "not sure" answer uses an assumed 1-in-4 chance of uncontrolled high blood pressure. More broadly, the research here describes population-level patterns; individual outcomes vary widely based on factors this calculator doesn’t capture. For your specific situation, consult a healthcare professional.
Factor
Social connection
In a meta-analysis of 90 cohort studies covering 2.2 million adults, social isolation was associated with about 32% higher all-cause mortality and loneliness with about 14% higher.
Years at stake
~1.9 years between the best and worst answer
For a 40-year-old in the US with otherwise typical habits. Smaller at older ages.
Strength of evidence
Limited
Declared as “associated with” — we don’t say “causes” unless the evidence supports it.
Sources
A systematic review and meta-analysis of 90 cohort studies of social isolation, loneliness and mortality.
Nature Human Behaviour, 2023·PubMed 37337095
Social connection
WHO·who.int
Limitations
Heavily confounded: poor health and depression can cause isolation as well as follow from it. More broadly, the research here describes population-level patterns; individual outcomes vary widely based on factors this calculator doesn’t capture. For your specific situation, consult a healthcare professional.