Professional calculator using Devine, Robinson, Miller, and Hamwi methods
Male
Female
Biological sex affects formula constants.
Imperial (Feet/Inches)
Metric (Centimeters)
Enter height in feet and inches.
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Enter height in centimeters.
Estimated Ideal Weight (Average)
166lbs
Based on the average of 4 major medical formulas
Healthy BMI Range
129 – 174 lbs
Devine Formula
166 lbs
Hamwi Formula
166 lbs
Formula Comparison
Formula
Result (lbs)
Result (kg)
Comparison of different medical standards for ideal body weight.
Visual comparison of calculated ideal weights
What is "How to Calculate Your Ideal Weight Formula"?
Understanding how to calculate your ideal weight formula is a fundamental step in assessing health and fitness goals. Unlike a simple scale reading, an ideal weight calculation uses mathematical formulas derived from population studies to estimate a healthy body weight based on height and gender. These formulas are widely used by medical professionals to determine drug dosages, assess nutritional needs, and set realistic weight management targets.
It is important to note that these formulas calculate "Ideal Body Weight" (IBW), which is a statistical average. It does not account for muscle mass, bone density, or age. Therefore, athletes or individuals with high muscle mass may find these results underestimate their healthy weight. However, for the general population, knowing how to calculate your ideal weight formula provides a solid baseline for health monitoring.
Ideal Weight Formulas and Mathematical Explanation
Over the last century, several formulas have been developed to answer the question of how to calculate your ideal weight formula. The most common ones are the Devine, Robinson, Miller, and Hamwi formulas. All of them follow a similar linear structure based on height over 5 feet.
The General Equation Structure
Weight = Base Weight + (Variable Rate × Inches over 5 feet)
1. Devine Formula (1974)
Originally developed for calculating drug dosages, this is the most widely used standard.
Men: 50.0 kg + 2.3 kg per inch over 5 feet
Women: 45.5 kg + 2.3 kg per inch over 5 feet
2. Hamwi Formula (1964)
Often used in clinical settings for quick estimations.
Men: 106 lbs + 6 lbs per inch over 5 feet
Women: 100 lbs + 5 lbs per inch over 5 feet
Variables Table
Variable
Meaning
Typical Unit
Base Weight
Starting weight for a 5ft person
kg or lbs
Height Factor
Weight added per unit of height
kg/inch or lbs/inch
Gender
Biological sex determinant
Male/Female
Practical Examples (Real-World Use Cases)
Example 1: Male, 5ft 10in
Let's apply the Devine formula to see how to calculate your ideal weight formula for a male who is 5 feet 10 inches tall.
Height over 5ft: 10 inches
Calculation: 50 kg + (2.3 kg × 10)
Result: 50 + 23 = 73 kg (approx. 161 lbs)
Interpretation: This individual has a medical ideal weight of roughly 73 kg. If they weigh 90 kg, they might be considered overweight unless they have significant muscle mass.
Example 2: Female, 5ft 4in
Using the Robinson formula for a female of average height.
Height over 5ft: 4 inches
Calculation: 49 kg + (1.7 kg × 4)
Result: 49 + 6.8 = 55.8 kg (approx. 123 lbs)
Interpretation: The Robinson formula tends to yield slightly lower values for women compared to Devine, suggesting a target of roughly 56 kg.
How to Use This Ideal Weight Calculator
Select Gender: Choose Male or Female. This adjusts the base weight and multiplier in the formula.
Choose Units: Select Imperial (Feet/Inches) or Metric (cm) depending on your preference.
Enter Height: Input your accurate height. The calculator requires height to be above 5 feet for standard formula accuracy (though it will calculate for shorter heights using subtraction).
Review Results: Look at the "Average" result for a balanced view, or check the specific formulas in the table below.
Check BMI Range: Compare the formula result with the Healthy BMI range (18.5–24.9) to see the broader window of healthy weight.
Key Factors That Affect Ideal Weight Results
When learning how to calculate your ideal weight formula, you must consider factors that the math ignores:
Muscle Mass: Muscle is denser than fat. A bodybuilder will weigh significantly more than their "ideal weight" but have a low body fat percentage.
Bone Density (Frame Size): People with large frames (wrist circumference) naturally weigh more. The Hamwi formula is often adjusted by ±10% to account for small or large frames.
Age: Metabolism slows and body composition changes with age. Older adults often carry slightly more weight, which can sometimes be protective against frailty.
Pregnancy: These formulas are not applicable during pregnancy.
Health Conditions: Fluid retention or other medical issues can skew weight readings, making the formula less relevant than body composition analysis.
Fat Distribution: Visceral fat (around organs) is more dangerous than subcutaneous fat. Two people with the same "ideal weight" can have vastly different health risks based on where they carry fat.
Frequently Asked Questions (FAQ)
Which formula is the most accurate?
No single formula is perfect. The Devine formula is the most widely used in medical settings for dosing, while the Hamwi formula is popular among dietitians. Averaging them gives a balanced view.
Does age affect how to calculate your ideal weight formula?
Strictly speaking, the formulas do not include an age variable. However, modern health guidelines suggest that a slightly higher BMI may be acceptable or beneficial for adults over 65.
Why is my ideal weight so low?
These formulas were developed decades ago when the population was generally leaner. They represent a statistical "ideal" for longevity, not necessarily modern aesthetic standards or athletic builds.
Can I use this if I am under 5 feet tall?
The standard formulas are designed for heights of 5 feet (60 inches) and above. For heights under 5 feet, the calculator subtracts weight based on the same rate, but accuracy decreases.
Is BMI better than Ideal Body Weight (IBW)?
BMI measures weight relative to height but doesn't distinguish fat from muscle. IBW gives a specific target number. Both are screening tools, not diagnostic tools.
How do I adjust for frame size?
A common rule of thumb with the Hamwi formula is to add 10% for a large frame and subtract 10% for a small frame.
Should I diet to reach this number?
Not necessarily. If you are healthy, active, and have good metabolic markers, your actual weight might be higher than the formula's result due to muscle. Consult a doctor before starting a weight loss plan.
How often should I recalculate?
Since the formula is based on height (which rarely changes for adults), the target number stays the same. You should track your actual weight against this target periodically.
Related Tools and Internal Resources
BMI Calculator – Calculate your Body Mass Index for a general health overview.