Free Ideal Weight Calculator
Find your healthy weight range using multiple scientific formulas. Compare Hamwi, Devine, Robinson, and Miller methods to find your target weight.
What Is Ideal Body Weight?
Ideal body weight (IBW) is an estimated weight range that's associated with optimal health outcomes based on your height and gender. It's been used in medical settings since the 1960s for drug dosing, nutritional assessment, and health guidance.
However, "ideal" weight is a concept, not a precise target. These formulas provide rough guidelines — your actual healthy weight depends on factors like muscle mass, body fat percentage, bone density, and overall health markers.
The Four Main Formulas Explained
Our calculator uses four well-established ideal weight formulas. Each was developed in different contexts and gives slightly different results:
1. Hamwi Formula (1964)
One of the oldest formulas, developed by Dr. George Hamwi for quick bedside estimates.
Men: 106 lbs for first 5 feet + 6 lbs per inch over 5 feet Women: 100 lbs for first 5 feet + 5 lbs per inch over 5 feet 2. Devine Formula (1974)
Created by Dr. Ben Devine for calculating drug dosages, this became the most widely used formula in medicine.
Men: 110 lbs + 5.06 lbs per inch over 5 feet Women: 100 lbs + 5.06 lbs per inch over 5 feet 3. Robinson Formula (1983)
Developed to improve on the Devine formula with better empirical support.
Men: 115.1 lbs + 4.19 lbs per inch over 5 feet Women: 108.4 lbs + 3.75 lbs per inch over 5 feet 4. Miller Formula (1983)
Tends to give higher ideal weights, which some consider more realistic for modern populations.
Men: 123.6 lbs + 3.09 lbs per inch over 5 feet Women: 119.1 lbs + 2.97 lbs per inch over 5 feet How Body Frame Affects Ideal Weight
Body frame size accounts for natural variation in skeletal structure. People with larger bone structures naturally weigh more at the same height.
How to Determine Your Frame Size
The most common method uses wrist circumference relative to height:
| Height | Small Frame | Medium Frame | Large Frame |
|---|---|---|---|
| Women | |||
| Under 5'2" | < 5.5" | 5.5" - 5.75" | > 5.75" |
| 5'2" - 5'5" | < 6" | 6" - 6.25" | > 6.25" |
| Over 5'5" | < 6.25" | 6.25" - 6.5" | > 6.5" |
| Men | |||
| Over 5'5" | < 6.5" | 6.5" - 7.5" | > 7.5" |
Frame Adjustments
- Small frame: Subtract 10% from ideal weight
- Medium frame: Use the calculated ideal weight as-is
- Large frame: Add 10% to ideal weight
Limitations of Ideal Weight Formulas
While useful as rough guidelines, ideal weight formulas have significant limitations:
❌ Don't Account for Muscle Mass
A muscular person will exceed their "ideal" weight while being very healthy. Athletes often weigh significantly more than formula predictions.
❌ Based on Older Populations
Most formulas were developed 40-60 years ago using different (often less diverse) study populations.
❌ Don't Consider Body Fat
Two people at the same height and weight can have vastly different body compositions and health outcomes.
❌ May Be Too Low for Some
The Devine formula in particular may predict weights that are lower than what many healthy individuals actually weigh.
Better Ways to Assess Healthy Weight
Instead of focusing solely on ideal weight formulas, consider a combination of metrics:
📏 Body Fat Percentage
Measures actual fat vs. lean mass. Calculate yours →
Healthy ranges: Men 10-20%, Women 18-28%
📐 Waist Circumference
Indicates visceral fat, which is linked to metabolic health.
Target: <40" men, <35" women
📊 Waist-to-Height Ratio
Your waist should be less than half your height.
Target: Keep it under 0.5
💪 Functional Fitness
Can you do daily activities easily? Can you exercise without issues?
This matters more than any number.
Setting Realistic Weight Goals
If you're above your ideal weight range and want to lose weight:
- Calculate your calorie deficit
Use our calorie deficit calculator to find a sustainable target.
- Aim for 0.5-1% of body weight per week
For a 200 lb person, that's 1-2 lbs per week. Faster loss often leads to muscle loss and rebounds.
- Prioritize protein and resistance training
Preserve muscle mass during weight loss. Calculate your protein needs →
- Focus on the upper end of your range
You don't need to hit the lowest formula prediction. The entire range is healthy.
- Reassess every 10-15 lbs
Your calorie needs change as you lose weight. Recalculate periodically.
What If You're Underweight?
Being significantly below your ideal weight range can also pose health risks:
- Weakened immune system
- Bone density loss (osteoporosis risk)
- Nutrient deficiencies
- Hormonal imbalances
- Reduced muscle mass and strength
If you're underweight and want to gain healthy weight:
- Eat in a calorie surplus (300-500 extra calories/day)
- Focus on protein (0.7-1g per pound body weight)
- Lift weights to build muscle, not just fat
- Consider consulting a healthcare provider or dietitian
Frequently Asked Questions
Common questions about ideal body weight
What is ideal body weight?
Ideal body weight (IBW) is an estimated weight range associated with good health outcomes based on your height and gender. It's a guideline, not a strict target — factors like muscle mass, body composition, and individual health should also be considered.
Which ideal weight formula is most accurate?
No single formula is universally 'most accurate.' The Devine formula is most commonly used in medical settings. The Robinson and Miller formulas tend to give slightly higher weights. We recommend looking at the range across all formulas rather than fixating on one number.
How much should I weigh for my height?
Your healthy weight range depends on height, gender, and body frame. For example, a 5'6" woman's ideal weight ranges from about 115-145 lbs across different formulas. A 5'10" man might range from 149-173 lbs. Use our calculator to find your personalized range.
Why does my ideal weight vary by formula?
Each formula was developed using different study populations and methodologies. Hamwi (1964) was designed for quick bedside estimates. Devine (1974) was created for medication dosing. Robinson and Miller (1983) attempted to improve accuracy. The variation shows that 'ideal weight' is a range, not a single number.
Is BMI or ideal weight better?
Both have limitations. BMI is simpler (just height and weight) but doesn't distinguish muscle from fat. Ideal weight formulas consider gender but not body composition. For a complete picture, combine ideal weight ranges with body fat percentage.
How does body frame affect ideal weight?
People with larger bone structures naturally weigh more at the same height. Body frame (small, medium, large) can adjust ideal weight by ±10%. Measure your wrist circumference to estimate frame size.
Should muscular people use ideal weight calculators?
Traditional ideal weight formulas don't account for above-average muscle mass. If you're muscular, you'll likely exceed these estimates while still being healthy. Focus on body fat percentage instead.
What's a healthy weight loss goal?
If your current weight is above your ideal range, aim to lose 0.5-1% of body weight per week. This typically means 1-2 lbs per week for most people. Sustainable weight loss is gradual.
Does age affect ideal weight?
Traditional formulas don't account for age, but research suggests slightly higher weights may be healthy for older adults (over 65), providing reserve for illness.
What if I'm below my ideal weight?
Being significantly underweight can increase health risks including weakened immunity, bone loss, and nutrient deficiencies. Consider consulting a healthcare provider about healthy weight gain.
References
- Hamwi GJ. Therapy: changing dietary concepts. Diabetes mellitus: diagnosis and treatment. 1964;1:73-78.
- Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8:650-655.
- Robinson JD, Lupkiewicz SM, Palenik L, Lopez LM, Ariet M. Determination of ideal body weight for drug dosage calculations. Am J Hosp Pharm. 1983;40(6):1016-1019. PubMed
- Miller DR, Carlson JD, Lloyd BJ, Day BJ. Determining ideal body weight. Am J Hosp Pharm. 1983;40(6):1622. PubMed