How Ideal Weight is Calculated (4 Formulas Compared)

There’s no single “perfect” weight — but doctors and nutritionists still use ideal body weight (IBW) formulas for drug dosing, setting fitness goals, and general health assessments. The catch? There are at least four popular formulas, and they don’t always agree.

The 4 major formulas

All four use height as the primary input and produce results in kilograms. They were originally designed for adults over 152 cm (5 ft).

Devine (1974):
  Male:   IBW = 50 + 2.3 × (height_in_inches − 60)
  Female: IBW = 45.5 + 2.3 × (height_in_inches − 60)

Robinson (1983):
  Male:   IBW = 52 + 1.9 × (height_in_inches − 60)
  Female: IBW = 49 + 1.7 × (height_in_inches − 60)

Miller (1983):
  Male:   IBW = 56.2 + 1.41 × (height_in_inches − 60)
  Female: IBW = 53.1 + 1.36 × (height_in_inches − 60)

Hamwi (1964):
  Male:   IBW = 48 + 2.7 × (height_in_inches − 60)
  Female: IBW = 45.5 + 2.2 × (height_in_inches − 60)

What the differences mean

• Devine is the most commonly used in clinical drug dosing
• Robinson tends to give slightly higher values for women
• Miller produces the highest results overall (more generous range)
• Hamwi was the earliest and tends to run higher for taller men

Worked example

Female, 5’6” (66 inches):

Devine:   45.5 + 2.3 × (66 − 60) = 45.5 + 13.8 = 59.3 kg
Robinson: 49 + 1.7 × (66 − 60)   = 49 + 10.2   = 59.2 kg
Miller:   53.1 + 1.36 × (66 − 60) = 53.1 + 8.16 = 61.3 kg
Hamwi:    45.5 + 2.2 × (66 − 60)  = 45.5 + 13.2 = 58.7 kg

The range here is 58.7–61.3 kg. Most practitioners accept ±10% of any formula result as a healthy range.

When to use it

• Setting a realistic fitness target with your trainer
• Understanding medication dosage calculations (Devine is standard)
• Getting a ballpark for healthy weight before using BMI or body fat analysis
• Comparing your frame size against population averages

Tips for better accuracy

• These formulas don’t account for muscle mass — a muscular person will weigh “above” IBW and still be healthy
• Frame size matters: add 10% for large frames, subtract 10% for small frames
• Use IBW as one data point alongside BMI, body fat percentage, and waist circumference
• Age isn’t factored in — older adults may have different healthy ranges

Try all four at once with OurDailyCalc’s ideal weight calculator and see which range fits your frame.

TL;DR

• Four popular formulas: Devine, Robinson, Miller, Hamwi
• All use height in inches; results differ by 2–5 kg
• Devine is the clinical standard for drug dosing
• Accept ±10% of any result as a healthy range
• Combine with BMI and body fat for a complete picture