How to Calculate Your Ideal Weight Based on BMI, Age, and Height
Discover different methods to determine your healthy weight range and understand which approach might be best for your body type and goals.
The concept of "ideal weight" has evolved significantly over the years. Rather than focusing on aesthetic standards or arbitrary numbers on a scale, modern health professionals prefer to think in terms of a healthy weight range that supports overall wellbeing.
There's no one-size-fits-all approach to determining what you should weigh. Your ideal weight depends on various factors including height, age, gender, body composition, and even genetic factors. In this article, we'll explore different methods to calculate a healthy weight range and discuss the strengths and limitations of each approach.
Important note: The methods described in this article provide general guidelines. For personalized advice about your ideal weight, consult with healthcare professionals who can consider your individual health status, medical history, and specific needs.
BMI-Based Method
The Body Mass Index (BMI) is one of the most widely used methods to determine whether someone is at a healthy weight. While it has limitations (which we'll discuss later), it provides a useful starting point.
How to calculate BMI:
BMI is calculated using the following formula:
BMI = weight (kg) / [height (m)]²
or
BMI = [weight (lbs) × 703] / [height (inches)]²
BMI categories:
| BMI Range | Weight Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 - 24.9 | Normal weight |
| 25.0 - 29.9 | Overweight |
| 30.0 and above | Obesity |
Calculating ideal weight range using BMI:
To determine your ideal weight range based on BMI, you can work backward from the healthy BMI range (18.5 - 24.9):
Ideal weight range = [18.5 to 24.9] × [height (m)]²
Example:
For someone who is 5'6" (167.6 cm or 1.676 m) tall:
- Lower end of healthy range: 18.5 × (1.676)² = 18.5 × 2.809 = 52.0 kg (114.6 lbs)
- Upper end of healthy range: 24.9 × (1.676)² = 24.9 × 2.809 = 70.0 kg (154.3 lbs)
So, the ideal weight range for someone who is 5'6" tall would be approximately 52-70 kg (115-154 lbs).
Use our BMI Calculator to quickly determine your BMI and see where you fall within these categories.
Broca Index
The Broca Index is an older method for calculating ideal weight that was popular before BMI became the standard. It's simpler but less accurate than some other methods.
The basic Broca formula:
Ideal weight (kg) = [height (cm) - 100]
Modified Broca formula:
The modified version adjusts for gender differences and tends to give more realistic results for most people:
For men: Ideal weight (kg) = [height (cm) - 100] × 0.9
For women: Ideal weight (kg) = [height (cm) - 100] × 0.85
Example:
For someone who is 5'6" (167.6 cm) tall:
- Basic Broca: 167.6 - 100 = 67.6 kg (149 lbs)
- Modified Broca (male): (167.6 - 100) × 0.9 = 60.8 kg (134 lbs)
- Modified Broca (female): (167.6 - 100) × 0.85 = 57.5 kg (127 lbs)
The Broca Index is easy to calculate but doesn't account for individual variations in body composition or frame size. It tends to underestimate ideal weight for taller people and overestimate it for shorter people.
Devine Formula
The Devine Formula was originally developed in 1974 to calculate drug dosages based on ideal body weight. It's still used in some medical contexts and provides a different approach to estimating ideal weight.
The Devine Formula:
For men: Ideal weight (kg) = 50 + 2.3 × [height (inches) - 60]
For women: Ideal weight (kg) = 45.5 + 2.3 × [height (inches) - 60]
This formula assumes that the ideal weight for a 5-foot (60 inches) tall man is 50 kg and for a 5-foot tall woman is 45.5 kg. For each inch over 5 feet, it adds 2.3 kg (about 5 lbs).
Example:
For someone who is 5'6" (66 inches) tall:
- Male: 50 + 2.3 × (66 - 60) = 50 + 2.3 × 6 = 50 + 13.8 = 63.8 kg (140.7 lbs)
- Female: 45.5 + 2.3 × (66 - 60) = 45.5 + 2.3 × 6 = 45.5 + 13.8 = 59.3 kg (130.7 lbs)
Other similar formulas:
Several variations of this approach exist:
Robinson Formula (1983):
For men: 52 + 1.9 × [height (inches) - 60]
For women: 49 + 1.7 × [height (inches) - 60]
These formulas give slightly different results, which highlights that "ideal weight" is not an exact science but rather an estimated range.
Use our Ideal Weight Calculator to compare results from different formulas.
Body Composition Approach
A more sophisticated way to determine your ideal weight is to focus on body composition—specifically, the ratio of fat mass to lean mass in your body. This approach recognizes that two people of the same height and weight can have very different body compositions and health profiles.
Healthy body fat percentage ranges:
| Category | Women | Men |
|---|---|---|
| Essential fat | 10-13% | 2-5% |
| Athletes | 14-20% | 6-13% |
| Fitness | 21-24% | 14-17% |
| Acceptable | 25-31% | 18-24% |
| Obesity | 32%+ | 25%+ |
Calculating ideal weight based on body fat percentage:
If you know your current body fat percentage, you can calculate your lean body mass and then determine what your weight would be at your target body fat percentage:
Current lean mass (kg) = Current weight (kg) × (1 - current body fat percentage)
Ideal weight (kg) = Current lean mass (kg) ÷ (1 - target body fat percentage)
Example:
For a woman who currently weighs 70 kg with 30% body fat who wants to reach 25% body fat:
- Current lean mass = 70 kg × (1 - 0.30) = 70 kg × 0.70 = 49 kg
- Ideal weight = 49 kg ÷ (1 - 0.25) = 49 kg ÷ 0.75 = 65.3 kg (144 lbs)
This approach is more personalized and accounts for individual differences in body composition. However, it requires knowing your current body fat percentage, which typically needs to be measured using specialized equipment like DEXA scans, bioelectrical impedance scales, or skinfold calipers.
Use our Body Fat Calculator to estimate your body fat percentage and calculate your ideal weight based on body composition.
Limitations of Ideal Weight Calculations
While these methods provide useful guidelines, they all have limitations and shouldn't be considered definitive measures of health or fitness:
They don't account for individual variations
Body frame size, muscle mass, bone density, and genetic factors all influence what a healthy weight is for each person. Two people of the same height might have very different "ideal" weights due to these factors.
BMI has known limitations
BMI doesn't distinguish between fat and muscle. Athletes and very muscular individuals often have a high BMI despite having low body fat. Conversely, some people with "normal" BMI may have unhealthy levels of body fat (sometimes called "skinny fat").
Age considerations are often missing
Most formulas don't account for how age affects body composition. As we age, we naturally lose muscle mass and gain fat, which can change what a healthy weight range looks like.
They don't consider fat distribution
Where you carry fat matters for health. Abdominal fat (especially visceral fat around organs) is more strongly linked to health risks than fat in other areas. Waist circumference and waist-to-hip ratio are important metrics that weight-based calculations don't capture.
Health is more than a number on the scale
Blood pressure, cholesterol levels, blood sugar, cardiovascular fitness, strength, flexibility, mental health, and overall quality of life are all important health indicators that aren't reflected in weight calculations.
Remember: The "ideal weight" calculations should be used as general guidelines rather than strict targets. Focus on overall health, sustainable habits, and how you feel rather than trying to achieve a specific number on the scale.
Conclusion
There's no single "perfect weight" that applies to everyone of a certain height or age. Your ideal weight is influenced by many factors including your body frame, muscle mass, age, gender, and overall health status.
The various calculation methods we've discussed can provide a general range to consider, but they should be used as just one tool among many to assess your health. Rather than fixating on a specific number, focus on:
- Maintaining a balanced diet rich in whole foods
- Regular physical activity that includes both cardio and strength training
- Adequate sleep and stress management
- Regular health check-ups to monitor important health markers
- How you feel physically and emotionally
If you're concerned about your weight or trying to determine the most appropriate weight range for your specific situation, consider consulting with healthcare professionals such as doctors, registered dietitians, or certified fitness professionals who can provide personalized guidance.
Remember that health comes in many shapes and sizes, and the number on the scale is just one of many factors that contribute to overall wellbeing.
Want to calculate your ideal weight?
Use our calculators to explore different methods and find your healthy weight range:
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