Ideal Weight Calculator
What is Ideal Body Weight?
Ideal body weight (IBW) is an estimate of a healthy weight based on height, gender, and sometimes age. It is used in clinical settings for drug dosing, nutritional assessment, and health risk evaluation. Common formulas include Hamwi, Devine, and BMI-based ranges.
How is Ideal Weight Calculated?
- BMI Range (18.5–24.9):
The Body Mass Index (BMI) is a widely used screening tool for healthy weight. A BMI between 18.5 and 24.9 is considered the "normal" or healthy range for adults. Ideal weight is calculated as the weight that would place you within this BMI range for your height. While BMI is simple and population-based, it does not distinguish between muscle and fat mass, and may not be accurate for athletes or older adults. - Hamwi Formula:
Developed in 1964 for clinical dietetics, the Hamwi formula estimates ideal body weight based on height and gender. It is commonly used for drug dosing and nutritional assessment. The formula is:
Men: 106 lbs + 6 lbs per inch over 5 ft
Women: 100 lbs + 5 lbs per inch over 5 ft
Hamwi is easy to calculate but may not account for body composition or ethnicity. - Devine Formula:
Introduced in 1974 for medication dosing, the Devine formula is similar to Hamwi but uses metric units. It is widely used in hospitals for calculating drug dosages. The formula is:
Men: 50 kg + 2.3 kg per inch over 5 ft
Women: 45.5 kg + 2.3 kg per inch over 5 ft
Devine is practical for clinical use but, like Hamwi, does not consider muscle mass or age. - Modern BMI-based Equation (Peterson et al., 2016):
This recent formula unifies BMI and ideal body weight concepts, allowing calculation of ideal weight for any target BMI and height. It is highly accurate and aligns with population health data. The equation is:
Wt (kg) = 2.2 × BMI + 3.5 × BMI × (Ht − 1.5 m)
This approach is flexible, sex-independent, and can be tailored to individual goals or health conditions. It is recommended for both clinical and general use.
| Formula | Gender-Specific? | Units | Based On | Best For |
|---|---|---|---|---|
| BMI Range | No | kg/cm | Population health | General screening |
| Hamwi | Yes | lbs/in | Height | Drug dosing (US) |
| Devine | Yes | kg/in | Height | Clinical dosing |
| Peterson | No | kg/m | BMI + height | Personalized goals |
Limitations of Ideal Weight Calculators
- Formulas provide estimates; individual needs vary due to genetics, age, ethnicity, and body composition.
- BMI does not distinguish between muscle and fat mass.
- Results may be less accurate for athletes, older adults, or those with atypical body types.
- Consult a healthcare professional for personalized advice.
Quick Guide:
- Medication dosing: Use Devine (or Hamwi for US settings).
- General fitness or health screening: Use BMI Range or Peterson.
- Athletes or those with high muscle mass: Prefer Peterson for flexibility.
- If you need a value for drug dosing, choose Devine (metric) or Hamwi (imperial).
- If you're interested in general health, BMI Range is simple and widely used.
- If you want a formula that adapts to your goals or body type, use Peterson.
When in doubt, try multiple methods and consult a healthcare professional for personalized advice.
Frequently Asked Questions (FAQ)
No single formula is perfect. BMI-based ranges and modern equations (Peterson et al., 2016) are most aligned with population health data.
Use ideal weight as a guideline, not a strict target. Focus on healthy habits and body composition.
Not always. Athletes may have higher muscle mass, making BMI and IBW formulas less accurate.
Yes, IBW formulas (Hamwi, Devine) are commonly used for drug dosing in clinical settings.
Each formula uses different assumptions about body composition, population averages, and health goals. Some are designed for clinical use, others for general health, which leads to varying results.
No. Ideal weight is a scientific estimate based on health data, while goal weight is personal and may reflect fitness, aesthetics, or athletic performance.
Muscle weighs more than fat, so individuals with high muscle mass may exceed ideal weight ranges but still be healthy. Formulas like BMI do not account for muscle mass.
References & Further Reading
- Peterson CM et al. (2016) - Universal equation for estimating ideal body weight and body weight at any BMI
- StatPearls - Secondary Causes of Obesity and Comprehensive Diagnostic Evaluation
- CDC - BMI Frequently Asked Questions
- WHO - Healthy Diet Factsheet
This calculator provides general estimates and is not a substitute for professional medical advice. Consult a healthcare provider before using these values for clinical decisions.