Ideal Weight Calculator | OmniCalculator

  • Adam
  • November 1, 2025

Free ideal body weight calculator using multiple formulas. Calculate IBW with Robinson, Miller, Devine, and Hamwi methods. Compare results and healthy BMI range.

⚖️ 📊 ⚖️

Ideal Weight Calculator

Calculate your ideal body weight using multiple formulas. Compare Robinson, Miller, Devine, and Hamwi methods for accurate estimates.

📋 Quick Navigation

⚖️ Enter your information to calculate ideal weight! 📊
2 - 100 years
in cm (100-250)
2 - 100 years
Average Ideal Weight
0 kg
Based on multiple formulas

Your Height

180
cm

Average IBW

74
kg

Healthy BMI Range

56-81
kg

📊 Formula Results

Formula Ideal Weight Year Developed
Robinson (1983) 0 kg Modified Devine
Miller (1983) 0 kg Modified Devine
Devine (1974) 0 kg Original Formula
Hamwi (1964) 0 kg Earlier Method

🧮 Ideal Weight Formulas Explained

Robinson Formula (1983) - Most Recommended

Modified version of Devine formula, widely considered the most accurate for modern populations.

For Men:
IBW = 52 kg + 1.9 kg per inch over 5'

For Women:
IBW = 49 kg + 1.7 kg per inch over 5'

Or in metric (height in cm):
Men: IBW = 52 + 1.9 × (Height - 152.4) / 2.54
Women: IBW = 49 + 1.7 × (Height - 152.4) / 2.54

Example: 180 cm male
Height above 5' = (180 - 152.4) / 2.54 = 10.9 inches
IBW = 52 + (1.9 × 10.9) = 52 + 20.7 = 72.7 kg

Miller Formula (1983) - Alternative

Similar accuracy to Robinson, slight variation in coefficients.

For Men:
IBW = 56.2 kg + 1.41 kg per inch over 5'

For Women:
IBW = 53.1 kg + 1.36 kg per inch over 5'

Devine Formula (1974) - Classic

The original formula, still widely used for medical dosing calculations.

For Men:
IBW = 50 kg + 2.3 kg per inch over 5'

For Women:
IBW = 45.5 kg + 2.3 kg per inch over 5'

Hamwi Formula (1964) - Early Method

Earlier formula, generally gives slightly higher estimates.

For Men:
IBW = 48.1 kg + 2.72 kg per inch over 5'

For Women:
IBW = 45.4 kg + 2.27 kg per inch over 5'

All Formulas in Metric

For direct calculation with height in centimeters:

Conversion: Height in inches = (Height cm - 152.4) / 2.54

Robinson: IBW = 52 + 1.9 × ((H - 152.4) / 2.54) male
Robinson: IBW = 49 + 1.7 × ((H - 152.4) / 2.54) female

📊 Formula Comparison & Accuracy

Which Formula Is Best?

Research suggests Robinson and Miller are most accurate for modern populations, giving results typically ±1-2 kg from each other. Devine, while classic, can give slightly different results. All are within 5-10 kg for most people.

Why Formulas Differ

Different formulas were developed using different populations, time periods, and methodologies. Robinson and Miller refined Devine based on newer data. Hamwi is the oldest and tends to give higher estimates. Averaging all four provides a robust estimate.

Accuracy by Height

Height Range Best Formula Notes
Short (<160 cm) Robinson or Miller Formulas work well for shorter heights
Average (160-190 cm) Any formula works well All formulas optimized for this range
Tall (>190 cm) Robinson, Miller, or Devine Hamwi may overestimate
💡 Pro Tip: Use the average of Robinson and Miller formulas for best results. This combines modern accuracy with validated methodology.

📐 Understanding IBW Calculation

What Is Ideal Body Weight (IBW)?

Ideal body weight is a target weight for health based on height and gender. Unlike BMI (which considers weight-to-height ratio), IBW formulas estimate a specific weight. Medical professionals use IBW for medication dosing, especially water-soluble drugs that distribute based on lean mass.

IBW vs Healthy Weight Range

IBW: Specific target weight from formulas. Healthy BMI Range: Weight range for BMI 18.5-25 (more flexible). Most people's ideal weight falls within their healthy BMI range, but not exactly.

When to Use IBW Formulas

  • Medical Dosing: Calculating medication doses
  • Fitness Goals: Target weight for training programs
  • Health Assessment: Quick estimate of healthy weight
  • Recovery Planning: Target weight during weight loss/gain

Important Limitations

IBW formulas don't account for: individual body composition, muscle mass, bone density, age-related changes, or ethnic variations. A very muscular person may weigh more than their IBW but be healthier. Use IBW as a guide, not an absolute target.

📌 Important: Ideal weight is a target, not a requirement for health. Focus on achieving healthy BMI and good body composition through nutrition and exercise. Individual factors vary significantly!

❓ Frequently Asked Questions

Should I aim for my exact ideal weight? +
No, ideal weight is a target range, not an exact number. Most healthy weights fall within ±5 kg of the calculated IBW. Focus on feeling good, fitting into clothes comfortably, and achieving healthy body composition rather than hitting a specific number. The number on the scale doesn't reflect health alone.
Why are formulas from 1964 still used? +
Hamwi (1964) was validated extensively and is still accurate for many populations. However, Robinson (1983) and Miller (1983) refine Hamwi and are considered more accurate for modern populations due to methodological improvements. Multiple formulas exist because different populations may respond better to different equations.
How does age affect ideal weight? +
Most IBW formulas don't directly adjust for age. However, metabolic rate decreases with age (about 2-8% per decade after 30), so actual calorie needs decrease. Your IBW stays the same, but you may find maintaining it requires less food. Strength training helps maintain muscle mass as you age.
What if my IBW seems too high or low? +
Consider your body composition. Athletes often weigh more due to muscle. Very sedentary people may naturally weigh less. Also check your height measurement - errors here significantly affect results. Compare your calculated weight to your healthy BMI range (18.5-25 kg/m²). If they align, the calculation is likely correct.
Do these formulas work for everyone? +
These formulas work well for most adults (18-65 years) of average body composition. They're less accurate for: very muscular individuals (underestimate), obese individuals (overestimate), children/adolescents (require different formulas), and very short/tall people (slight inaccuracy). Use clinical judgment for special populations.
Can I change my ideal weight? +
Your calculated IBW is based on height and gender, which don't change. However, through muscle building and strength training, you can increase your healthy weight at the same body fat percentage. Or through body composition changes, you could achieve better health at a lower weight. The formula gives a target; your actual goal depends on your body composition and fitness.
How do I reach my ideal weight safely? +
Gradual changes work best: lose 0.5-1 kg per week or gain 0.25-0.5 kg per week. Combine strength training (builds muscle), balanced nutrition (adequate protein), and cardio. Aim for 80% of calories from whole foods. Get 7-9 hours sleep nightly. Consider consulting a registered dietitian for personalized guidance. Remember that health is multifactorial - weight is just one factor.
Should I aim for the same weight as the calculator? +
Use the calculated weight as guidance, not a mandate. If you're healthy, feel good, and within your BMI range, your current weight is likely fine. These formulas provide estimates within ±5 kg typical accuracy. Focus on fitness, nutrition, and how you feel rather than obsessing over reaching an exact number.

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