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.
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Enter your details
Your Estimated Life Expectancy
ExampleExample figures, not your own. Worked for a 40 year old man of 175 cm going from 95 kg to 80 kg. Enter your own details and press Calculate.
Estimated Years Gained by Reaching Goal Weight
+5.8
additional years of life expectancy
At Current Weight
75years old
BMI 31.0 - estimated 35.2 more years
At Goal Weight
81years old
BMI 26.1 - estimated 41.0 more years
Life Expectancy Timeline
Medical Disclaimer
This calculator provides statistical estimates based on population-level research data from the Australian Bureau of Statistics Life Tables and the Global BMI Mortality Collaboration (The Lancet, 2016). It does not account for individual health conditions, family history, ethnicity, socioeconomic factors, smoking, alcohol use, physical activity, or diet quality. These estimates are for educational and motivational purposes only and should not be interpreted as medical advice. Always consult a qualified healthcare professional such as your GP, an Accredited Practising Dietitian, or an exercise physiologist before making changes to your diet or exercise routine. If you have concerns about your weight or health, please speak with your doctor.
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.
How to use it
- 1Enter your current age in years
- 2Select your sex (male or female)
- 3Enter your height in centimetres
- 4Enter your current weight in kilograms
- 5Enter your goal weight in kilograms
- 6Click "Calculate" to see your estimated life expectancy at both weights
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
- 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.