Ideal Weight Calculator Formula
Understand the math behind the ideal weight calculator. Each variable explained with a worked example.
Formulas Used
Ideal Weight (kg)
ideal_weight_kg = 50 + 2.3 * (total_inches - 60)Ideal Weight (lbs)
ideal_weight_lbs = (50 + 2.3 * (total_inches - 60)) * 2.20462Variables
| Variable | Description | Default |
|---|---|---|
height_feet | Height (feet)(ft) | 5 |
height_inches | Height (inches)(in) | 10 |
total_inches | Derived value= height_feet * 12 + height_inches | calculated |
How It Works
Devine Formula for Ideal Body Weight (Male)
Ideal Weight (kg) = 50 + 2.3 x (height in inches - 60)
This formula was originally developed for calculating medication dosages and is now widely used as a general health guideline.
Note: This is the male formula. The female formula uses 45.5 kg as the base.
Worked Example
A male who is 5 feet 10 inches tall.
- 01Total height = 5 x 12 + 10 = 70 inches
- 02Inches over 5 feet = 70 - 60 = 10
- 03Ideal weight = 50 + 2.3 x 10 = 73.0 kg
- 04In pounds = 73.0 x 2.205 = 160.9 lbs
When to Use This Formula
- Getting a reference range to discuss with your doctor before setting a weight loss or weight gain goal, especially after a significant health event.
- Medication dosing in clinical settings where ideal body weight (IBW) is used instead of actual weight to calculate safe drug doses — particularly for aminoglycosides and chemotherapy agents.
- Anesthesia planning where tidal volume and ventilator settings are based on ideal body weight rather than actual weight to avoid lung injury.
- Setting a starting-point goal weight as part of a fitness plan, understanding that the result is a reference range, not a single exact number.
Common Mistakes to Avoid
- Treating the result as a definitive healthy weight — the Devine formula was created for drug dosing, not as a health target. It does not account for muscle mass, bone density, frame size, or ethnicity.
- Applying the formula to people under 5 feet tall — the Devine formula starts at 5 feet (60 inches) and adds weight per inch above that. It produces no meaningful result for shorter individuals.
- Using the wrong sex-specific formula — the male formula starts at 50 kg for 5 feet and the female formula starts at 45.5 kg. Swapping them shifts the result by about 10 pounds.
- Confusing ideal body weight with adjusted body weight — for obese patients in clinical settings, adjusted body weight (IBW + 0.4 × (actual - IBW)) is often used instead of IBW alone.
Frequently Asked Questions
What is the Devine formula?
The Devine formula was created by Dr. B.J. Devine in 1974 to estimate ideal body weight for drug dosing. It uses height in inches as the primary input: for men, IBW = 50 + 2.3 kg per inch over 5 feet; for women, IBW = 45.5 + 2.3 kg per inch over 5 feet.
Is ideal body weight the same for everyone?
No. Ideal weight varies by body frame size (small, medium, large), muscle mass, age, and individual health factors. The Devine formula provides a general starting guideline, not a definitive target.
What is the difference between ideal body weight and healthy weight range?
Ideal body weight (IBW) is a single target number based on height, originally designed for medication dosing. A healthy weight range is broader, typically defined by a BMI of 18.5-24.9, giving a lower and upper bound based on your height.
What if I weigh more than my ideal body weight?
Being above your calculated IBW does not automatically mean you are unhealthy. Athletes and muscular individuals often exceed the IBW because the formula does not account for muscle mass. Use BMI and body fat percentage together for a more complete health picture.
Learn More
Guide
Understanding BMI: What It Means and How to Calculate It
Learn what BMI is, how to calculate it, what the ranges mean, and the limitations of body mass index as a health metric. Comprehensive guide with formulas and context.
Ready to run the numbers?
Open Ideal Weight Calculator