Ideal Weight Calculator
Find your ideal body weight using four established formulas: Devine, Robinson, Miller, and Hamwi, with frame size adjustment.
Results
Visualization
How It Works
Ideal body weight (IBW) formulas estimate a healthy target weight based on height and gender. Four classic formulas are commonly used: Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964). Because each was developed for a different purpose and population, comparing all four gives a more reliable range than relying on any single formula.
The Formula
Variables
- IBW — Ideal Body Weight in kilograms
- inches over 5ft — Height in inches above 60 inches (152.4 cm)
- Frame adjustment — Multiplier: 0.9 for small frame, 1.0 for medium, 1.1 for large
Worked Example
A 170 cm male with medium frame: inches over 60 = (170 - 152.4) / 2.54 = 6.93. Devine = 50 + 2.3*6.93 = 65.9 kg. Robinson = 52 + 1.9*6.93 = 65.2 kg. Miller = 56.2 + 1.41*6.93 = 65.97 kg. Hamwi = 48 + 2.7*6.93 = 66.7 kg. Average = 66.0 kg.
Practical Tips
- These formulas were designed for adults over 152 cm (5 feet) tall; they are less reliable for shorter individuals.
- Frame size matters: wrap your thumb and middle finger around your wrist. If they overlap, you have a small frame; if they touch, medium; if a gap remains, large.
- Ideal weight formulas do not account for muscle mass. A fit, muscular person may healthily weigh more than the formula suggests.
- Use the average of all four formulas as your target rather than any single one.
- These formulas provide a reference point, not a strict goal. Health markers like blood pressure and blood sugar matter more than a number on the scale.
Frequently Asked Questions
Which ideal weight formula is the most accurate?
No single formula is definitively best. The Devine formula is most commonly used in clinical settings for drug dosing, while Robinson and Miller tend to give slightly lower estimates. Averaging all four provides the most balanced target for general health purposes.
Why do the formulas give different results?
Each formula was developed using different populations and for different purposes. Devine's was originally for calculating medication dosages, Hamwi's for quick clinical estimates. The variations typically span 2-5 kg, reflecting the natural range of healthy weights.
Does frame size really matter?
Yes, skeletal frame size affects how much you should weigh. A large-framed person has heavier bones and can carry more weight healthily. The 10% adjustment for small and large frames is a well-accepted clinical approximation.
Are these formulas appropriate for all ages?
These formulas were developed for adults. For children and adolescents, growth charts and BMI-for-age percentiles from the CDC or WHO are more appropriate. Older adults may also benefit from slightly higher weight targets, as mild overweight is associated with better outcomes in those over 65.
My current weight is far from the ideal. What should I do?
Consult a healthcare provider before making major changes. A safe rate of weight loss is 0.5-1 kg per week. Focus on sustainable dietary changes and regular physical activity rather than crash diets. Even a 5-10% reduction from your current weight can significantly improve health markers.