Determine your healthy weight range using medically approved formulas and BMI standards.
Metric (kg, cm)
Imperial (lbs, ft/in)
Male
Female
Biological sex affects bone density and muscle mass assumptions in formulas.
Please enter a valid height (50-300 cm).
Please enter a valid height.
Used for general health context.
Estimated Normal Weight Range (BMI)
56.7 – 76.6 kg
Based on a healthy BMI of 18.5 – 25.0
Ideal Weight (Devine)70.0 kg
Ideal Weight (Robinson)68.5 kg
Ideal Weight (Miller)69.0 kg
Weight Comparison Chart
Visual comparison of your current weight vs. healthy ranges.
Detailed Formula Breakdown
Formula / Method
Calculated Weight
Description
These formulas estimate ideal body weight based on height and gender.
What is "Normal" Body Weight?
Understanding how to calculate your normal body weight is a fundamental step in assessing your overall health and fitness. The term "normal" or "ideal" body weight (IBW) refers to a weight range associated with the lowest risk of weight-related diseases, such as type 2 diabetes, hypertension, and cardiovascular issues.
It is important to note that a single number cannot define health for everyone. "Normal" weight is a spectrum that varies based on height, gender, body frame size, and muscle mass. While the Body Mass Index (BMI) is the most common screening tool, older medical formulas like the Devine and Robinson equations provide specific weight targets often used in clinical settings for medication dosing.
This guide and calculator are designed for adults (18+). Athletes with high muscle mass may find that standard BMI calculations classify them as overweight, which is a known limitation of the metric.
Formulas and Mathematical Explanation
To accurately determine how to calculate your normal body weight, we utilize several established medical formulas. Each has a slightly different methodology.
1. Body Mass Index (BMI) Range
The World Health Organization defines a "normal" BMI as being between 18.5 and 24.9. The formula to reverse-calculate weight from BMI is:
Weight = BMI × (Height in meters)²
Lower Limit: 18.5 × (Height)²
Upper Limit: 24.9 × (Height)²
2. The Devine Formula (1974)
Originally developed to calculate drug dosages, this is the most widely used formula for Ideal Body Weight (IBW).
Men: 50.0 kg + 2.3 kg per inch over 5 feet
Women: 45.5 kg + 2.3 kg per inch over 5 feet
3. The Robinson Formula (1983)
A modification of the Devine formula based on updated actuarial data.
Men: 52 kg + 1.9 kg per inch over 5 feet
Women: 49 kg + 1.7 kg per inch over 5 feet
Variables Table
Variable
Meaning
Unit
Typical Range
Height
Vertical stature
Meters / Inches
1.5m – 2.0m
Base Weight
Starting constant
kg
45.5 – 56.2 kg
Increment
Weight added per inch
kg/inch
1.36 – 2.7 kg
Key variables used in IBW calculations.
Practical Examples
Example 1: The Average Male
Scenario: John is a 30-year-old male, 5 feet 10 inches tall (178 cm).
Height over 5ft: 10 inches.
Devine Calculation: 50 kg + (2.3 kg × 10) = 73 kg (approx. 161 lbs).
BMI Range: 18.5 to 24.9 BMI equates to a weight range of roughly 58.5 kg to 79 kg.
Interpretation: John's "normal" weight is a range. If he weighs 73 kg, he is right in the center of the ideal zone according to the Devine formula.
Example 2: The Petite Female
Scenario: Sarah is a 25-year-old female, 5 feet 4 inches tall (163 cm).
Height over 5ft: 4 inches.
Robinson Calculation: 49 kg + (1.7 kg × 4) = 55.8 kg (approx. 123 lbs).
BMI Range: A healthy BMI range for her height is approximately 49 kg to 66 kg.
Interpretation: While the Robinson formula suggests ~56 kg, Sarah is considered to have a normal body weight anywhere up to 66 kg, depending on her frame size.
How to Use This Calculator
Select Unit System: Choose between Metric (kg/cm) or Imperial (lbs/ft).
Enter Gender: Formulas differ significantly between men and women due to physiological differences.
Input Height: Be as accurate as possible. Even an inch or centimeter can shift the result.
Input Current Weight (Optional): This allows the tool to calculate your current BMI and compare it to the ideal range.
Review Results: Look at the "Estimated Normal Weight Range" for the broadest definition of health, and the specific formulas for a targeted "ideal" number.
Key Factors That Affect Normal Body Weight
When learning how to calculate your normal body weight, consider these six critical factors that formulas often miss:
1. Muscle Mass vs. Fat Mass
Muscle is denser than fat. A bodybuilder may weigh significantly more than the "ideal" weight calculated by these formulas but have a low body fat percentage and excellent metabolic health.
2. Bone Density (Frame Size)
People with larger bone structures (large frames) naturally weigh more. The Hamwi formula sometimes adjusts for frame size by adding or subtracting 10%, but standard calculators often assume a medium frame.
3. Age
As we age, we tend to lose muscle and gain fat. However, some studies suggest that a slightly higher BMI in older adults (over 65) may be protective against mortality, suggesting "normal" weight might shift upward slightly with age.
4. Gender
Women generally have a higher essential body fat percentage than men. This is why formulas like Devine and Robinson have lower base weights and increments for women.
5. Pregnancy and Lactation
Standard BMI and IBW formulas do not apply to pregnant or breastfeeding women. Weight gain is a necessary and healthy part of pregnancy.
6. Fat Distribution
Where you carry weight matters. Visceral fat (around the organs) is more dangerous than subcutaneous fat (under the skin). Two people can have the same "normal" weight, but if one carries it all in the abdomen, they may have higher health risks.
Frequently Asked Questions (FAQ)
Which formula is the most accurate?
The Devine formula is the most widely used in medical settings for dosing medications. However, for general health, the BMI range (18.5–24.9) is the standard screening tool used by the WHO and CDC.
Is BMI accurate for athletes?
No. BMI does not distinguish between muscle and fat. Athletes often have high BMIs despite having low body fat. In these cases, body fat percentage is a better metric than weight.
What if I am outside the "normal" range?
Being outside the range does not automatically mean you are unhealthy. It is a signal to consult a healthcare provider to assess other markers like blood pressure, cholesterol, and blood sugar.
Does frame size matter?
Yes. A person with a small frame should aim for the lower end of the calculated range, while someone with a large frame may be healthy at the upper end or slightly above.
How often should I weigh myself?
Weekly weighing is generally recommended over daily weighing to account for normal water weight fluctuations without causing obsession.
Why do the formulas give different results?
They were developed in different years using different population data. The Miller formula (1983), for example, often yields a higher weight estimate than the Devine formula.
Can I use this for children?
No. Children and teenagers require specialized growth charts (BMI-for-age percentiles) because they are still growing.
What is the "Hamwi" method?
The Hamwi method is a quick rule of thumb: 106 lbs for the first 5 feet + 6 lbs per inch for men, and 100 lbs + 5 lbs per inch for women. It is very similar to the Devine formula.
Related Tools and Resources
Explore more tools to help you manage your health and fitness journey:
BMI Calculator – A dedicated tool for Body Mass Index screening.