Ideal Weight Converter
Calculate and convert ideal body weight using Devine, Robinson, Miller, Hamwi, and BMI-based formulas. Supports frame size adjustment and multiple units.
Ideal Weight Converter
Calculator
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Formula: Devine(M): 50 + 2.3(in over 60) | Devine(F): 45.5 + 2.3(in over 60) | Frame: small x0.9, large x1.1
Worked example — Average ideal weight: approximately 71.6 kg (157.9 lb)
Formula
Devine(M): 50 + 2.3(in over 60) | Devine(F): 45.5 + 2.3(in over 60) | Frame: small x0.9, large x1.1
Ideal body weight formulas use height in inches above 60 inches (5 feet) as the base. Each formula applies a different per-inch increment. Gender determines the base weight. Frame size adjusts the result by plus or minus 10%. The BMI-based method uses 21.75 as the midpoint of the healthy BMI range.
Worked Examples
Example 1: Average Male Ideal Weight
Problem:Calculate ideal weight for a 5 ft 10 in (177.8 cm) male with medium frame.
Solution:Inches over 60: 70 - 60 = 10 Devine: 50 + 2.3(10) = 73 kg (160.94 lb) Robinson: 52 + 1.9(10) = 71 kg (156.53 lb) Miller: 56.2 + 1.41(10) = 70.3 kg (154.98 lb) Hamwi: 48 + 2.7(10) = 75 kg (165.35 lb) BMI: 21.75 x 1.778^2 = 68.74 kg (151.55 lb)
Result:Average ideal weight: approximately 71.6 kg (157.9 lb)
Example 2: Small Frame Female
Problem:Calculate ideal weight for a 165 cm female with small frame.
Solution:Height in inches: 165 / 2.54 = 64.96 in Inches over 60: 4.96 Devine: (45.5 + 2.3 x 4.96) x 0.9 = 51.12 kg Frame adjustment: multiply by 0.9 for small frame
Result:Average ideal weight (small frame): approximately 51-55 kg (112-121 lb)
Frequently Asked Questions
What formulas are used to calculate ideal body weight?
This converter uses five well-known formulas: Devine (1974), Robinson (1983), Miller (1983), Hamwi (1964), and a BMI-based method. Each uses height and gender to estimate ideal weight, with the base being weight at 5 feet (60 inches) plus an increment per inch above that. The Devine formula is the most widely used in clinical settings, particularly for drug dosing calculations. Results vary between formulas because each was derived from different population studies and methodologies.
How does body frame size affect ideal weight?
Body frame size adjusts the ideal weight estimate by approximately 10% in either direction. A small frame reduces the estimate by 10%, while a large frame increases it by 10%. You can estimate your frame size by wrapping your thumb and index finger around your wrist. If they overlap you have a small frame, if they just touch it is medium, and if there is a gap it is a large frame. The Metropolitan Life Insurance tables from 1983 were among the first to incorporate frame size into ideal weight charts.
Is ideal body weight the same as healthy weight?
Ideal body weight formulas provide estimates based primarily on height and gender, but healthy weight depends on many additional factors including age, muscle mass, bone density, body composition, and overall health. A bodybuilder may weigh well above their calculated ideal weight yet be perfectly healthy. The BMI range of 18.5 to 24.9 is generally considered healthy, but individual assessment by a healthcare provider is more reliable than any single formula.
How do I convert ideal weight between kilograms and pounds?
To convert kilograms to pounds, multiply by 2.20462. To convert pounds to kilograms, divide by 2.20462 or multiply by 0.453592. For example, an ideal weight of 70 kg equals 154.32 pounds. This converter automatically displays results in both units so you can use whichever measurement system you prefer. In medical contexts, kilograms are standard worldwide for drug dosing and clinical calculations.
How do the Robinson and Devine formulas differ?
Both are linear in height above 60 inches but use different constants. Devine sets the base at 50 kg for men and 45.5 kg for women, adding 2.3 kg per inch. Robinson raises the male base slightly and cuts the increment: 52 kg plus 1.9 kg per inch for men, and 49 kg plus 1.7 kg per inch for women. Robinson therefore reads higher at short stature and lower at tall stature. At 74 inches, Devine gives 50 + 2.3 x 14 = 82.2 kg while Robinson gives 52 + 1.9 x 14 = 78.6 kg.
How does the BMI-based method estimate ideal weight?
Rather than a per-inch increment, this method inverts the BMI definition. BMI is mass in kilograms over height in metres squared, so choosing a target BMI and multiplying by height squared returns a weight. The tool uses 21.75, the midpoint of the commonly cited 18.5 to 24.9 healthy range. At 175 cm, height squared is 1.75 x 1.75 = 3.0625 square metres, so the estimate is 21.75 x 3.0625 = 66.6 kg. Because it scales with the square of height rather than linearly, it diverges from the linear formulas at the extremes.
Why is the Devine formula associated with pharmacokinetic dosing?
Devine was originally published as a dosing aid rather than as a health target. Many drugs distribute mainly into lean tissue and body water rather than into fat, so scaling by total body weight can overshoot in people carrying more adipose tissue. An ideal body weight estimate acts as a stand-in for lean mass that needs only height and sex, which makes it quick and reproducible. Which weight descriptor a particular medication calls for is set by its own protocol, so this explains the reasoning rather than giving dosing guidance.
What is adjusted body weight and when is it used?
Adjusted body weight sits between ideal and actual weight, and is commonly computed as ideal weight plus a fraction, often 0.4, of the difference between actual and ideal weight. The reasoning is that additional body mass is not purely fat, since it carries some extra lean tissue and expanded blood volume, so neither ideal nor actual weight alone describes the distributing compartment well. It appears in calculations where the quantity of interest tracks lean mass but is not strictly proportional to total mass.
Why do the five formulas disagree for the same height and sex?
Each was fitted to a different reference population, using different methods and in a different decade, from Hamwi in 1964 through Devine in 1974 to Robinson and Miller in 1983. The underlying insurance and clinical datasets varied in age range, ethnic composition and how height was measured. Miller in particular uses a much smaller increment, 1.41 kg per inch for men, which flattens the curve at tall heights. Reading the spread across all five estimates is more informative than trusting any single output.
How reliable are these estimates below five feet of height?
Every formula here is anchored at 60 inches and adds a fixed increment per inch above that, so at exactly 60 inches they collapse to their base constants and below that they have no defined extension. This tool clamps the inches-over-60 term at zero, which means shorter heights all return the same base value rather than a scaled one. Extrapolating downward by subtracting the increment is not supported by the source data either, so for short stature the estimates should be treated as unreliable.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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