We've split the atom, spliced the gene, even sent a spacecraft to Mars. But finding a reliable way to predict a person's life span? That's proven a bit more difficult. In recent years, however, scientists have begun to crack the code-identifying 22 genetic, demographic, and lifestyle factors that can estimate life span with a surprising amount of accuracy. Want to find your magic number? Read on to calculate your life expectancy.

Longevity Wizard

Although no prediction is set in stone, it is possible to estimate your life span based on the following factors. Each factor-and the amount of years it adds or subtracts from your baseline life expectancy-is documented by hundreds of medical studies.

1. Your Gender: According to the World CIA Factbook, average American life expectancy at birth is 75 for men and 81 for women. If you're male, start with a baseline life expectancy number of 75; if you're female, start with 81.

2. Your Age: In general, the later you were born, the longer you'll live, since you'll benefit from incremental advances in health care. However, if you've already reached the age of 65, you may also enjoy an additional longevity boost (the theory is that you've already proven your durability and can therefore expect to reach a ripe old age). If you're part of the Greatest Generation (born 1901 to 1924) or Silent Generation (born 1925 to 1945), add two years; if you're part of the Baby Boomer Generation (born 1946 to 1960), don't add or subtract. If you're part of Generation X (born 1960 to 1979), add one year. If you're part of Generation Y (born 1980 to 2001), add three years.

3. Your Marital Status: Numerous studies have confirmed that married people, and especially married men, live longer than their divorced, widowed, or never-married counterparts. If you're a married man, add five years to your baseline life expectancy; if you're a married woman, add two years. If you're an unmarried, divorced, or widowed man, subtract five years; if you're an unmarried, divorced, or widowed woman, subtract two years.

4. Your Education Level: A recent study conducted at Harvard Medical School found that life expectancy for those with college educations was significantly higher than for those with only a high school education or less. If you have more than 12 years of education (some college, a college diploma, or graduate degree), add two years to your baseline life expectancy; if you have 12 years' education or less, subtract two years.

5. Your Financial Income: According to the National Center for Health Statistics, there's a clear correlation between longevity and socioeconomic status. If your household income is more than $75,000, add two years to your baseline life expectancy; if it's between $50,000 and $74,000, add one year; and if it's between $35,000 and $49,000, don't add or subtract. If your household income is less than $35,000, subtract one year.

6. Your Location: Studies suggest that if you live in a rural environmental, you'll have a better chance of reaching an old age than your urban counterparts. Add two years to your baseline life expectancy if you've lived most of your life in a rural area; subtract two years if you've lived most of your life in a city; and don't add or subtract if you live in the suburbs.

7. Your Family History: Decoding your DNA can be tricky, but there's a lot you can learn by looking at your family tree. If two or more of your grandparents lived to be 80 or older, add four years to your baseline life expectancy. If a family member (parent, sibling, or grandparent) died of a heart attack or stroke before the age of 50, subtract four years; if a family member died of a heart attack or stroke before the age of 60, subtract two years. In addition, subtract three years for every case of heart disease, diabetes, and breast or digestive-system cancer among your parents, siblings, or grandparents.

8. Your Medical History: Not surprisingly, certain diagnoses are associated with shorter life spans than others. Subtract three years from your baseline life expectancy if you've been diagnosed with high blood pressure or high cholesterol; subtract seven years if you've been diagnosed with heart disease, diabetes, cancer, or COPD.

9. Your Weight/BMI: An overwhelming amount of research shows a strong relationship between body mass index (BMI) and life expectancy. If your BMI is less than 25 (normal), add two years to your baseline life expectancy. If it's 25 to 30 (overweight), subtract two years, and if it's more than 30 (obese), subtract five years. 

10. Your Smoking Habits: Smoking can affect your life span more dramatically than any other lifestyle factor. If you smoke two or more packs a day, subtract eight years from your baseline life expectancy; if you smoke one to two packs a day, subtract five years; and if you smoke less than one pack a day, are regularly exposed to secondhand smoke, or smoke cigars or a pipe, subtract two years.

11. Your Drinking Habits: While heavy drinking can shorten your life span, light drinking can lengthen it. If you're a heavy drinker (more than four drinks a day), subtract seven years from your baseline life expectancy; if you're a light drinker (one to three drinks a day), add two years; if you're a light drinker who generally consumes red wine, add three years; if you don't drink, don't add or subtract.

12. Your Eating Habits: A healthy diet with plenty of fresh fruit, vegetables, whole grains, and unsaturated fats can boost your lifespan, while an unhealthy diet that's high in fast foods, red meat, sugar, and trans or saturated fats can have the opposite effect. Add three years to your baseline life expectancy if you eat a healthy diet, and subtract three years if you eat an unhealthy diet. If your diet is about average, don't add or subtract.

13. Your Exercise Levels: Physical fitness is one of the best ways to reduce your disease risk and boost your longevity. Add five years to your baseline life expectancy if you engage in vigorous activity three times a week or more, and add three years if you engage in moderate activity three times a week or more. If you live a sedentary lifestyle, subtract three years.

14. Your Sleep Habits: Chronic sleep deprivation can shorten your life span, but getting too much shut-eye can reduce it even more, according to a 2002 study published in the Archives of General Psychiatry. Add two years to your baseline life expectancy if your sleep between six and eight hours a night, subtract two years if you sleep less than six hours a night, and subtract three years if you sleep more than eight hours a night.

15. Your Safety Habits: Sadly, automobile accidents are the leading cause of death for Americans ages 4 to 34. If you always wear a seat belt when you're in a car (whether you're the driver or a passenger), add one year to your baseline life expectancy; if you wear a seat belt most of the time, don't add or subtract; if you wear a seat belt about half of the time, subtract one year; and if you wear one less than half of the time, subtract two years.

16. Your Sun Exposure: An estimated 1 million Americans are diagnosed with skin cancer every year, and although only a small percentage die of the disease, it can increase your risk for premature death. If you always reduce your UV exposure by wearing protective clothing, staying out of the sun in midday, and wearing a broad-spectrum sunscreen with an SPF of at least 15, add one year to your baseline life expectancy; if you don't take these preventative measures, subtract one year.

17. Your Flossing Habits: Numerous studies have confirmed that good dental hygiene can boost your heart health and your longevity. If you floss your teeth every day, add two years to your baseline life expectancy; if you don't, subtract two years.

18. Your Ability to Deal With Stress: It's often said that stress can shorten your life, but a growing body of research indicates that it's the way you handle stress-not your stress level itself-that has a greater influence on life expectancy. If stress eats away at you or makes you angry, subtract three years from your baseline life expectancy; if stress motivates you in a positive way or if you're able to easily shed stress with relaxation techniques, such as exercise or yoga, add three years; if you're somewhere in between, don't add or subtract.

19. Pet Ownership: Owning a pet, especially a dog, can add years to your life. In fact, survival rates of heart attack victims are 28 percent higher for those who own a pet than for those who don't. Add three years to your baseline life expectancy if you own a dog, add two years if you own a cat or other animal companion, and subtract one two years if you're not a pet owner.

20. Preventative Medical Care: One of the easiest ways to lengthen your life span is going to the doctor for regular checkups, which should include a blood pressure test, age-appropriate screenings, immunizations, and an analysis of your risk factors. If you've been to the doctor for a checkup in the past year, add two years to your baseline life expectancy; if your last visit was one to two years ago, don't add or subtract; if your last visit was more than two years ago, subtract two years.

21. Your Outlook: A 2002 study conducted by the Mayo Clinic found that optimistic people were 50 percent less likely to suffer early death than pessimists. Add two years to your baseline life expectancy if you're an optimistic person, subtract two years if you're a pessimist, and don't add or subtract if you're in between.

22. Your Family and Friendships: Studies have shown that people who maintain close relationships with friends and family generally outlive those who don't. Add three years to your baseline life expectancy if you see close friends and family at least three times a week; subtract two years if you don't.

Now that you've crunched the numbers, you can take proactive steps to boost your longevity. Visit our Health Centers for more information on reducing your disease risks and boosting your life span.