How to Calculate Your Ideal Weight: Complete Guide with Formulas and Calculator
Have you ever wondered how much you should weigh based on your height? The answer is more nuanced than a single number. "Ideal weight" isn't a universal figure — it depends on your height, body frame, age, biological sex, and even your muscle composition. In this complete guide, we explain the most widely used formulas, their differences, their limitations, and how to interpret the results realistically.
Start right now with our ideal weight calculator to get your personalized range in seconds.
What Is Ideal Weight?
Ideal weight is a range of body weight considered healthy for a person based on specific physical characteristics, primarily height. It's not an exact number but a reference zone that helps identify whether someone is underweight, at a healthy weight, overweight, or obese.
It's important to understand that ideal weight is a guidance tool, not a medical diagnosis. Two people with the same height can have different ideal weights depending on their muscle mass, bone density, and other individual factors.
Why Should You Know Your Ideal Weight?
- Set realistic goals for weight loss or gain
- Assess health risks associated with being underweight or overweight
- Plan appropriate nutrition with support from a dietitian
- Track progress over time in a health program
The Main Formulas for Calculating Ideal Weight
Over the years, doctors and nutritionists have developed different formulas to estimate a healthy weight. Here are the most well-known and widely used ones.
The Lorentz Formula
The Lorentz formula is one of the most popular and differentiates between men and women:
For men:
Ideal weight (kg) = Height (cm) − 100 − [(Height (cm) − 150) / 4]
For women:
Ideal weight (kg) = Height (cm) − 100 − [(Height (cm) − 150) / 2]
Example: A woman who is 165 cm tall:
- Ideal weight = 165 − 100 − [(165 − 150) / 2]
- Ideal weight = 65 − [15 / 2]
- Ideal weight = 65 − 7.5 = 57.5 kg
A man who is 175 cm tall:
- Ideal weight = 175 − 100 − [(175 − 150) / 4]
- Ideal weight = 75 − [25 / 4]
- Ideal weight = 75 − 6.25 = 68.75 kg
The Broca Formula
The Broca formula is simpler and one of the oldest, developed by French surgeon Paul Broca in 1871:
For men:
Ideal weight (kg) = Height (cm) − 100
For women:
Ideal weight (kg) = Height (cm) − 105
Example: For a woman who is 165 cm:
- Ideal weight = 165 − 105 = 60 kg
This formula is quick to calculate mentally, but tends to overestimate ideal weight for shorter people and underestimate it for taller individuals.
The Devine Formula
This formula was originally designed to calculate medication doses and is most widely used in U.S. medical contexts:
For men:
Ideal weight (kg) = 50 + 2.3 × (Height in inches − 60)
For women:
Ideal weight (kg) = 45.5 + 2.3 × (Height in inches − 60)
Example: For a man who is 175 cm (approximately 68.9 inches):
- Ideal weight = 50 + 2.3 × (68.9 − 60)
- Ideal weight = 50 + 2.3 × 8.9
- Ideal weight = 50 + 20.47 = 70.47 kg
Body Mass Index (BMI)
Although BMI is not exactly a "ideal weight" formula, it is the most globally used tool to evaluate whether someone is within a healthy range. It's calculated by dividing weight by the square of height:
BMI = Weight (kg) / [Height (m)]²
| Category | BMI Range | |----------|-----------| | Underweight | Below 18.5 | | Normal weight | 18.5 – 24.9 | | Overweight | 25.0 – 29.9 | | Obesity Class I | 30.0 – 34.9 | | Obesity Class II | 35.0 – 39.9 | | Obesity Class III | 40.0 or higher |
You can check your BMI with our BMI calculator.
To find your ideal weight using BMI, solve for weight using a BMI of 22 (midpoint of the healthy range):
Ideal weight ≈ 22 × [Height (m)]²
Example: For someone who is 1.70 m tall:
- Ideal weight ≈ 22 × (1.70)² = 22 × 2.89 = 63.6 kg
Formula Comparison: Which One Should You Use?
| Formula | Accuracy | Ease of Use | Gender-Specific | Best For | |---------|----------|-------------|-----------------|----------| | Lorentz | High | Medium | Yes | Adults 20–65 years | | Broca | Low-Medium | High | Yes | Quick estimates | | Devine | High | Low | Yes | Medical context | | BMI (target weight) | Medium | High | No | General assessment |
Recommendation: For most Latin American adults, the Lorentz formula offers a good balance between accuracy and simplicity. For a more complete assessment, combine it with the BMI method.
Factors That Influence Your Real Ideal Weight
Formulas are starting points, not absolute truths. Several personal factors can make your real ideal weight different from the calculated one:
1. Body Frame
People with wider, denser bones (large frame) will naturally weigh more than someone with a small frame at the same height. You can estimate your body frame by measuring your wrist circumference:
| Frame | Woman (height >163 cm) | Man | |-------|------------------------|-----| | Small | Wrist < 15.2 cm | Wrist < 16.5 cm | | Medium | 15.2 – 16.5 cm | 16.5 – 19.1 cm | | Large | > 16.5 cm | > 19.1 cm |
2. Body Composition (Muscle vs. Fat)
An athlete with significant muscle mass may have a BMI of 27 or 28 — technically "overweight" — but with a perfectly healthy body fat percentage. Traditional formulas don't distinguish between muscle and fat.
If you exercise regularly, also consider checking your body fat percentage and basal metabolic rate with our basal metabolism calculator.
3. Age
Natural muscle loss (sarcopenia) occurs with aging. Some formula variants adjust ideal weight for older adults, allowing slightly broader ranges after age 65.
4. Ethnicity and Regional Context
The World Health Organization (WHO) recognizes that Asian populations face greater metabolic risk at lower BMI values than Europeans. In Guatemala and Central America, the indigenous Maya population tends to have a shorter average stature, which should be considered when interpreting these values.
How to Interpret Your Current Weight vs. Ideal Weight
Once you calculate your ideal weight, the next step is understanding the gap with your current weight:
If you're below your ideal weight:
- May indicate low caloric intake, nutritional issues, or underlying conditions
- Consult a doctor or nutritionist
- The goal would be to gain weight healthily, prioritizing muscle over fat
If you're within the healthy range:
- Maintain your eating habits and physical activity
- Do periodic check-ins to monitor changes
If you're above your ideal weight (overweight or obese):
- Don't panic: formulas provide ranges, not verdicts
- A moderate caloric deficit (300–500 kcal/day) is the most sustainable weight-loss strategy
- Consult a professional before starting restrictive diets
- Track your progress monthly, not daily
Practical Steps to Reach Your Ideal Weight
- Calculate your ideal weight using the Lorentz formula or our ideal weight calculator
- Measure your current BMI with the BMI calculator
- Estimate your basal metabolism to know how many calories you need per day
- Set a realistic plan: losing 0.5 to 1 kg per week is safe and sustainable
- Consult a health professional if the gap between your current and ideal weight is more than 10 kg
Frequently Asked Questions
How much should a 5'3" (160 cm) woman weigh?
Using the Lorentz formula:
- Ideal weight = 160 − 100 − [(160 − 150) / 2] = 60 − 5 = 55 kg (121 lbs)
Using the BMI method (target BMI of 22):
- Ideal weight ≈ 22 × 1.60² = 22 × 2.56 = ~56.3 kg (124 lbs)
The healthy range for a 160 cm woman is approximately 52 to 64 kg (115–141 lbs) (BMI 20–25).
How much should a 5'9" (175 cm) man weigh?
Using Lorentz:
- Ideal weight = 175 − 100 − [(175 − 150) / 4] = 75 − 6.25 = 68.75 kg (152 lbs)
Healthy range (BMI 20–25): approximately 61 to 77 kg (135–170 lbs).
Is ideal weight the same as healthy weight?
Not exactly. "Ideal weight" is a mathematical estimate based on your height. "Healthy weight" is a broader concept that includes body composition, blood sugar levels, blood pressure, and other metabolic indicators. You can be at your "ideal weight" and still have unhealthy habits.
Do these formulas work for children and teenagers?
No. The formulas in this article are for adults. For children and adolescents, age- and sex-specific growth percentile charts are used, established by the WHO and other pediatric organizations.
Conclusion
Calculating your ideal weight is a valuable first step to understanding your body health, but it should never be the only indicator. Formulas give you a reference range; your doctor, lab results, and overall wellbeing complete the picture.
Use our ideal weight calculator to get your personalized range, and complement it with the BMI calculator and basal metabolism calculator for a more complete view of your health.
Remember: the goal isn't to hit a perfect number on the scale — it's to feel good, have energy, and reduce long-term health risks.