How accurate is this life expectancy calculator?

This calculator provides population-level statistical estimates, not individual predictions. The underlying data comes from the Australian Bureau of Statistics and a meta-analysis of 10.6 million participants. However, individual life expectancy depends on many factors not captured here, including genetics, smoking, physical activity, diet, alcohol use, and existing medical conditions. Use this as a motivational tool, not a medical prognosis.

What data sources does this calculator use?

It uses two primary sources: the Australian Bureau of Statistics Life Tables 2020-2022 (Catalogue 3302.0) for baseline life expectancy by age and sex, and the Global BMI Mortality Collaboration study published in The Lancet in 2016, which analysed 10.6 million participants across 239 prospective studies to determine mortality risk by BMI category.

How does BMI affect life expectancy?

According to the Global BMI Mortality Collaboration, each 5 kg/m2 increase in BMI above 25 is associated with approximately 31% higher all-cause mortality. A person with a BMI of 30-35 has a 45% higher mortality risk than someone with a BMI of 22.5-25. At BMI 40+, the risk is 176% higher. Being underweight (BMI under 18.5) also carries increased mortality risk.

Can losing weight really help me live longer?

Research consistently shows that maintaining a healthy BMI (22.5-25) is associated with the lowest all-cause mortality risk. For people who are overweight or obese, losing weight to move closer to this range can reduce the risk of heart disease, type 2 diabetes, certain cancers, and other obesity-related conditions. Even modest weight loss of 5-10% of body weight can produce meaningful health benefits.

Life Expectancy Calculator

This Life Expectancy Calculator estimates how reaching a healthier weight could affect your lifespan. It combines official Australian life tables from the ABS with mortality risk data from the Global BMI Mortality Collaboration, one of the largest studies ever conducted on BMI and death risk, covering 10.6 million people across 239 studies published in The Lancet.

Enter Your Details

Age

years

Sex

Height

Current Weight

Goal Weight

How It Works

Your baseline life expectancy is looked up from Australian Bureau of Statistics Life Tables (2020-2022) based on your age and sex. Your BMI is then calculated from your height and weight, and a hazard ratio from the Global BMI Mortality Collaboration (Lancet, 2016) is applied to adjust the baseline. The same adjustment is calculated for your goal weight, and the difference shows the estimated years of life you could gain. A conservative square-root dampening factor is used because BMI-related mortality risk diminishes somewhat with advancing age.

Quick Reference

BMI Range	Category	Mortality Risk vs Healthy BMI
Under 18.5	Underweight	+13-47% higher
18.5 - 22.4	Normal (lower)	Reference / +13%
22.5 - 24.9	Normal (upper)	Reference (lowest risk)
25.0 - 27.4	Overweight I	+7% higher
27.5 - 29.9	Overweight II	+20% higher
30.0 - 34.9	Obese Class I	+45% higher
35.0 - 39.9	Obese Class II	+94% higher
40.0+	Obese Class III	+176% higher

Source: Global BMI Mortality Collaboration, The Lancet (2016). Based on 10.6 million participants across 239 studies.

How This Estimate Is Calculated

Adjusted Years = Baseline Years x (1 / Hazard Ratio)^0.5

Baseline Years: = remaining life expectancy from ABS Life Tables by age and sex
Hazard Ratio: = all-cause mortality risk for your BMI range (Global BMI Mortality Collaboration)
^0.5: = square root dampening factor (conservative estimate, as BMI impact diminishes with age)

This is a statistical estimate based on population-level data. Individual outcomes depend on many factors including genetics, medical history, diet, physical activity, smoking, and alcohol consumption. This calculator is for educational purposes only and does not constitute medical advice.

Frequently Asked Questions

How accurate is this life expectancy calculator?: This calculator provides population-level statistical estimates, not individual predictions. The underlying data comes from the Australian Bureau of Statistics and a meta-analysis of 10.6 million participants. However, individual life expectancy depends on many factors not captured here, including genetics, smoking, physical activity, diet, alcohol use, and existing medical conditions. Use this as a motivational tool, not a medical prognosis.
What data sources does this calculator use?: It uses two primary sources: the Australian Bureau of Statistics Life Tables 2020-2022 (Catalogue 3302.0) for baseline life expectancy by age and sex, and the Global BMI Mortality Collaboration study published in The Lancet in 2016, which analysed 10.6 million participants across 239 prospective studies to determine mortality risk by BMI category.
How does BMI affect life expectancy?: According to the Global BMI Mortality Collaboration, each 5 kg/m2 increase in BMI above 25 is associated with approximately 31% higher all-cause mortality. A person with a BMI of 30-35 has a 45% higher mortality risk than someone with a BMI of 22.5-25. At BMI 40+, the risk is 176% higher. Being underweight (BMI under 18.5) also carries increased mortality risk.
Can losing weight really help me live longer?: Research consistently shows that maintaining a healthy BMI (22.5-25) is associated with the lowest all-cause mortality risk. For people who are overweight or obese, losing weight to move closer to this range can reduce the risk of heart disease, type 2 diabetes, certain cancers, and other obesity-related conditions. Even modest weight loss of 5-10% of body weight can produce meaningful health benefits.

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