Ideal Weight Formula Comparison
Predicting your Ideal Body Weight (IBW) provides a realistic, healthy target range for weight loss, fitness goals, and medical dosage calculations.
In clinical medicine, Ideal Body Weight is calculated using established mathematical formulas (such as the Devine Formula, Robinson Formula, and Miller Formula) that base optimal weight primarily on biological gender and height above 5 feet (152.4 cm). In addition, the NHS defines a healthy weight range as any weight that yields a BMI between 18.5 and 24.9 kg/m².
⚙️ Rules & Thresholds
- Devine Formula (Clinical Gold Standard):
- Men:
50 kg + 2.3 kg for every inch of height over 5 feet. - Women:
45.5 kg + 2.3 kg for every inch of height over 5 feet.
- Men:
- NHS Healthy Weight Range Formula:
Minimum Healthy Weight (kg) = 18.5 × (Height in metres)².Maximum Healthy Weight (kg) = 24.9 × (Height in metres)².
- Height Threshold: Clinical IBW formulas assume a minimum baseline height of 5 feet (60 inches / 152.4 cm).
📊 Practical Examples
- Biological Gender: Male | Height: 175 cm (68.9 inches = 8.9 inches over 5 ft)
- Current Weight: 82.0 kg (12 st 12 lbs)
- Devine Formula IBW: 50 kg + (2.3 × 8.9) = **70.47 kg** (11 st 1 lb)
- NHS Healthy BMI Weight Range: **56.7 kg to 76.3 kg**
- Weight Difference to Reach Devine Ideal: **-11.53 kg** (reduce weight by 11.5 kg)
Result: The Devine ideal weight is 70.5 kg, situated comfortably in the middle of the NHS healthy weight range (56.7 kg – 76.3 kg).
📑 Common Pitfalls
- Confusing a Single Ideal Weight with a Rigid Requirement: Health is a range; any weight within the NHS healthy BMI band (BMI 18.5 to 24.9) represents a healthy weight.
- Ignoring Frame Size and Muscle Density: Individuals with naturally broad skeletal frames or high muscle mass can sit comfortably above theoretical IBW targets without excess body fat.
- Setting Unrealistic Rapid Weight Loss Goals: Attempting to reach an ideal weight too quickly (> 1 kg/week) causes muscle wasting and metabolic slowdown.
❓ Frequently Asked Questions (FAQ)
The Devine formula is a medical equation developed in 1974 by Dr. Ben J. Devine to estimate ideal body weight for drug dosage calculations. It sets a baseline weight for a 5-foot person (50 kg for men, 45.5 kg for women) and adds 2.3 kg per inch above 5 feet.
The NHS defines a healthy weight range for any adult as a weight that produces a Body Mass Index (BMI) between 18.5 and 24.9 kg/m². For example, for a person 175 cm tall, the healthy weight range is 56.7 kg to 76.3 kg.
Standard IBW formulas do not adjust for age. However, research suggests that slightly higher BMI ranges (BMI 23 to 27) in older adults over age 65 are associated with better health resilience and protection against illness.
70 kg equals approximately 154.3 pounds (lbs), which is 11 stone 0.3 lbs. To convert kg to stones, multiply by 0.157473.