The Devine formula is one of the most widely used short-hand ways to estimate a "ideal" body weight from a person's height. It was developed by Dr. B. J. Devine in 1974 as a simple way to dose medications by body size, and it has since become a standard reference in clinical pharmacology. This calculator applies the exact Devine equation, converts the result into both kilograms and pounds, and then compares it with your actual BMI so you can see where you stand relative to the formula's target.
Unlike a generic "healthy weight" range, the Devine formula gives a single number: about 106 lbs for a 5-foot male and 100 lbs for a 5-foot female, adding roughly 5 lbs (2.3 kg) for every inch above 5 feet. It is deliberately simple — one equation, two sexes, one height input — which is exactly why clinicians and researchers still reach for it decades later.
How to Use
- Select your Sex. The formula uses a different starting weight for men (50 kg) and women (45.5 kg), so this choice changes the result.
- Enter your Height (total inches). Convert your height into total inches first: 5 feet 9 inches is (5 × 12) + 9 = 69 inches. Every inch above 60 inches adds 2.3 kg to the target.
- Optionally type your Current Weight in pounds. Leave it blank if you only want the ideal-weight number; entering it lets the calculator show your actual BMI and how many pounds you are above or below the Devine target.
- Read the result card: your ideal body weight in kg and lbs, your actual BMI, the BMI category that BMI falls into, and the gap (positive means you are above the target).
The engine rejects any height that is zero or negative, because an invalid height cannot produce a meaningful target weight.
The Devine Formula Explained
The equation is compact on purpose. For adults:
- Male: Ideal body weight (kg) = 50 + 2.3 × (height in inches − 60)
- Female: Ideal body weight (kg) = 45.5 + 2.3 × (height in inches − 60)
The "−60" anchors the formula at 5 feet (60 inches). A man exactly 5 feet tall lands on 50 kg (about 110 lbs); a woman of the same height lands on 45.5 kg (about 100 lbs). Every additional inch — whether you are 65 or 72 inches tall — adds a flat 2.3 kg, because Devine assumed an idealized proportional body build. To convert the kilogram result to pounds, multiply by 2.20462.
The formula then compares that target against your BMI, which is your weight in kilograms divided by the square of your height in meters. A BMI under 18.5 is classified as underweight, 18.5–24.9 as normal, 25–29.9 as overweight, and 30 or above as obese. Note that the Devine target for an average-height adult usually corresponds to a BMI near 21–22 — comfortably inside the "normal" band but slightly below its middle.
Examples
Example 1 — A 5'9" man at his target. Enter Sex = male, Height = 69 in, Current Weight = 155.87 lbs. Ideal kg = 50 + 2.3 × 9 = 70.7 kg, which converts to 155.87 lbs. His actual BMI works out to about 23.0, squarely in the normal range, and the difference from ideal is 0.0 lbs.
Example 2 — A 5'4" woman who weighs 132 lbs. Enter Sex = female, Height = 64 in, Current Weight = 132 lbs. Ideal kg = 45.5 + 2.3 × 4 = 54.7 kg, or 120.59 lbs. Her actual BMI is about 22.7 (normal), and she is 11.4 lbs above the Devine target. That gap is small — within the roughly 10% tolerance most clinicians treat as acceptable.
Example 3 — Seeing the gap. A 6-foot (72 in) man enters 200 lbs. His Devine target is 50 + 2.3 × 12 = 77.6 kg (about 171.1 lbs), while his BMI is roughly 27.2, placing him in the overweight category about 29 lbs above target. That is roughly 17% above the Devine number. Sliding the current weight down shows both the BMI number and the gap move toward zero.
FAQ
What is the Devine formula?
The Devine formula is a 1974 equation for estimating ideal body weight. For men it is 50 + 2.3 × (inches − 60) kg, and for women 45.5 + 2.3 × (inches − 60) kg. It was originally designed to guide medication dosing and is still widely cited in clinical settings.
How accurate is the ideal body weight it gives?
It is an estimate, not a diagnosis. The formula assumes an "ideal" proportional build and ignores muscle mass, frame size, age, and body composition. Many healthy adults sit within about 10% above or below the number it produces, so treat the result as a reference point rather than a strict target.
How does the Devine target compare with BMI?
For an average-height adult the Devine number usually maps to a BMI of roughly 21–22, which sits inside the normal BMI range (18.5–24.9). This calculator shows both so you can cross-check: the Devine figure is a single target weight, while BMI is a ratio that works directly from your actual height and weight.
Why is there a different starting weight for men and women?
Devine set the baseline at 50 kg (about 110 lbs) for a 5-foot male and 45.5 kg (about 100 lbs) for a 5-foot female. That roughly reflects the typical difference in lean body mass between sexes at the same height. Above 5 feet the formula adds the same 2.3 kg per inch to both groups.
Can I use this formula for children or teenagers?
No. The Devine formula was built for adults and assumes a fully grown skeleton. For children and adolescents, growth charts and age- and sex-specific BMI percentiles are the appropriate tools.
What is a healthy range around the Devine number?
A common practical rule of thumb is plus or minus 10% of the ideal weight. So a 70.7 kg (155.87 lb) target corresponds to a healthy span of roughly 63.6–77.8 kg (140–171 lbs) — about ±10% on either side.
Disclaimer
This Devine formula calculator is provided for informational purposes only and is not medical advice. The ideal-weight figures and BMI categories it produces are estimates based on the published Devine equation and standard BMI cutoffs; individual health depends on body composition, medical history, age, and many other factors that this tool cannot capture. Always consult a qualified healthcare professional before making changes to your diet, activity, or medication, and never rely on an online calculator to diagnose or treat any condition.