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Introduction
Every ideal weight calculator relies on a specific mathematical formula. You might assume these equations came from rigorous medical research involving large, diverse populations. In reality, most originated from insurance company data collected in the mid-20th century. They were designed to predict mortality risk, not to define what any individual should weigh.
Understanding these ideal weight formulas helps you interpret the numbers you see. It also explains why different calculators sometimes give you slightly different results. This guide walks through the five most common equations, how they differ, and which one tends to work best for specific situations.
For an overview of how to use these numbers in a broader health context, see our pillar post on ideal weight calculators . For a discussion of what the numbers miss entirely, read our guide to factors affecting ideal weight .
The Devine Formula (1974)
The most widely used ideal weight formula today was created by Dr. B.J. Devine in 1974. Interestingly, he developed it not for health purposes but to calculate medication dosages based on body weight.
The formula is simple. For men, it starts at 50 kg and adds 2.3 kg for every inch over 5 feet. For women, it starts at 45.5 kg and also adds 2.3 kg for every inch over 5 feet. A 5-foot-10-inch man would have a Devine ideal weight of approximately 73 kg (about 161 pounds). A 5-foot-5-inch woman would land around 57 kg (about 125 pounds).
Because of its widespread adoption in clinical settings, the Devine formula serves as the default for most online calculators. However, it was developed using a relatively narrow population and may not perfectly represent all body types.
The Robinson Formula (1983)
The Robinson formula arrived in 1983 as a refinement of Devine’s work. Researchers Robinson and Miller published it with slight adjustments.
For men, the Robinson formula calculates 52 kg plus 1.9 kg per inch over 5 feet. For women, it calculates 49 kg plus 1.7 kg per inch over 5 feet. Compared to Devine, the Robinson formula generally produces slightly lower ideal weights, particularly for taller individuals. For our 5-foot-10-inch man, Robinson would suggest around 71 kg instead of Devine’s 73 kg.
This formula draws from mortality data collected by the Metropolitan Life Insurance Company. Like Devine, it reflects the population it studied rather than a universal human ideal.
The Miller Formula (1983)
The same year, researchers also published the Miller formula, which differs more significantly from Devine than Robinson does.
For men, the Miller formula calculates 56.2 kg plus 1.41 kg per inch over 5 feet. For women, it calculates 53.1 kg plus 1.36 kg per inch over 5 feet. The Miller formula typically produces lower ideal weights than both Devine and Robinson, especially for taller individuals.
The differences between these three 1983 formulas—Miller and Robinson published simultaneously—illustrate how much the choice of formula can shift your result. A 6-foot man would see a spread of roughly 8 kg between the three equations.
The Hamwi Formula (1964)
The Hamwi formula actually predates Devine by a decade. It was published in 1964 by Dr. G.J. Hamwi.
For men, Hamwi calculates 48 kg plus 2.7 kg per inch over 5 feet. For women, it calculates 45.5 kg plus 2.2 kg per inch over 5 feet. For our 5-foot-10-inch man, Hamwi would suggest about 75 kg—slightly heavier than Devine.
The Hamwi formula uses a steeper slope for men, meaning it adds more weight per inch of height than other formulas. This produces higher ideal weights for taller men compared to Robinson or Miller.
The Lemmens Formula (2005)
The newest of the group, the Lemmens formula, arrived in 2005 and takes a different approach. Rather than starting from a base weight, it uses a multiplier tied to BMI.
The formula calculates ideal weight as 22 times height in meters squared. It applies the same calculation to men and women. For a 5-foot-10-inch man (about 1.78 meters), this produces approximately 69.7 kg. This corresponds to a BMI of 22, which sits in the middle of the healthy range.
Because it does not differentiate by gender and uses BMI as its foundation, the Lemmens formula often produces results that align more closely with modern public health guidelines.
Which Formula Should You Trust?
No single ideal weight formula works perfectly for everyone. The Devine formula remains the most widely used and serves as a reasonable starting point. The Robinson formula may work better for taller individuals, while the Lemmens formula aligns well with BMI-based health guidelines.
The most useful approach is not to choose one formula but to consider the range they produce together. If several formulas cluster around a similar number, that number likely represents a reasonable target for someone of your height and gender.
For tools that do this calculation automatically, see our list of best online ideal weight calculators .
Conclusion
Ideal weight formulas are mathematical estimates, not medical verdicts. The Devine, Robinson, Miller, Hamwi, and Lemmens formulas each reflect the era and population that produced them. Understanding their differences helps you interpret the numbers you see on any calculator. For a deeper look at the factors these formulas ignore—like muscle mass, age, and bone structure—read our guide to factors affecting ideal weight .
