What is "Ideal Body Weight"?
"Ideal body weight" (IBW) is a rough estimate of a healthy weight for a given height and sex. The concept originated in the medical community, not the fitness world — the original IBW formulas were developed for calculating medication dosages, not for setting fitness goals.
That said, IBW formulas can be useful as a reference point. They give you a ballpark number to compare against your current weight, which combined with other metrics (BMI, body fat percentage) gives you a fuller picture of where you stand.
Formulas Used
This calculator uses four widely-cited formulas for estimating ideal body weight. They all produce slightly different numbers, which is why we show all four plus the average.
Devine Formula (1974)
The most commonly referenced IBW formula in clinical medicine. Dr. B.J. Devine originally developed it for calculating drug dosages. It's been the default in many hospital pharmacies for decades.
- Men: IBW = 50 kg + 2.3 kg per inch over 5 feet
- Women: IBW = 45.5 kg + 2.3 kg per inch over 5 feet
Robinson Formula (1983)
A refinement of the Devine formula with updated coefficients based on more recent population data. Generally gives slightly lower numbers than Devine.
- Men: IBW = 52 kg + 1.9 kg per inch over 5 feet
- Women: IBW = 49 kg + 1.7 kg per inch over 5 feet
Miller Formula (1983)
Another modern refinement. Tends to give slightly higher estimates, especially for taller individuals. Less commonly used in clinical practice than Devine or Robinson.
- Men: IBW = 56.2 kg + 1.41 kg per inch over 5 feet
- Women: IBW = 53.1 kg + 1.36 kg per inch over 5 feet
Hamwi Formula (1964)
One of the earliest IBW formulas, developed for diabetes management. Still commonly cited in clinical settings despite its age. Tends to give slightly higher estimates than Devine.
- Men: IBW = 48 kg + 2.7 kg per inch over 5 feet
- Women: IBW = 45.5 kg + 2.2 kg per inch over 5 feet
Worked Example
Let's calculate ideal weight for a 5'7" woman (67 inches, or 7 inches over 5 feet):
- Devine: 45.5 + 7 × 2.3 = 61.6 kg = 136 lbs
- Robinson: 49 + 7 × 1.7 = 60.9 kg = 134 lbs
- Miller: 53.1 + 7 × 1.36 = 62.6 kg = 138 lbs
- Hamwi: 45.5 + 7 × 2.2 = 60.9 kg = 134 lbs
- Average: (136 + 134 + 138 + 134) / 4 = 136 lbs
Her average ideal weight across formulas is about 136 lbs. The BMI-based healthy range (BMI 18.5-24.9) for 5'7" is 118-159 lbs — so "ideal" falls near the middle of the BMI healthy range.
Important Considerations and Limitations
IBW formulas have significant limitations you should understand before interpreting your result.
They don't account for muscle mass
IBW formulas assume average body composition. A muscular person could weigh well above their calculated IBW while being perfectly healthy. This is the same limitation as BMI — these formulas were never designed to distinguish muscle from fat.
They don't account for frame size
People with larger skeletal frames naturally weigh more than people with smaller frames of the same height, even at the same body fat percentage. IBW formulas don't capture this variation. Your "ideal" might be 10-15 lbs higher or lower than the calculated number depending on your frame.
They assume average proportions
IBW formulas were based on population averages from decades ago. They may be less accurate for very short people, very tall people, or certain ethnic groups with different body proportions.
They aren't designed for athletes
Serious athletes often weigh 15-30 lbs above their calculated IBW due to added muscle mass. For athletes, IBW is largely irrelevant — sport-specific performance metrics and body fat percentage matter much more.
Ideal doesn't necessarily mean healthiest
Research has actually shown that modest overweight (BMI 25-27) may be associated with slightly lower all-cause mortality in older adults than "normal" weight. This is the "obesity paradox." The concept of a single "ideal" weight is overly simplistic for health purposes.
When IBW is Useful
- Ballpark target for goal-setting. If you're significantly overweight, IBW gives a rough target to work toward.
- Medical reference. Used in some medication dosing and surgical planning.
- Comparison tool. Seeing how your current weight compares to multiple formulas provides a sanity check.
- Starting point for conversation. With a dietitian or doctor, IBW can anchor discussions of realistic goals.
When to Ignore IBW
- You have significant muscle mass (lifter, athlete)
- You're an older adult where higher BMI may actually be protective
- You have a medical condition affecting body composition
- You're pregnant
- You're under 20 (use pediatric standards instead)
Better Alternatives for Fitness Goals
For fitness and body composition goals, IBW isn't the best target. More useful metrics include:
- Body fat percentage. Directly measures composition, not just weight. Calculate yours here.
- Waist circumference. Abdominal fat specifically predicts cardiovascular risk.
- Strength benchmarks. How much you can squat, bench, deadlift — these track functional fitness.
- Cardiovascular fitness. How far you can run, how quickly you recover — these predict longevity better than weight.
- Blood markers. Cholesterol, blood pressure, HbA1c — these measure actual metabolic health.
Using Multiple Metrics Together
No single metric tells the full story. A complete assessment combines several:
- Calculate your ideal weight (this page)
- Calculate your BMI
- Estimate your body fat percentage
- Measure your waist circumference
- Consider your fitness goals, not just weight
When all these metrics roughly agree, you're probably in the right place. When they disagree strongly (e.g., BMI says overweight but body fat is 12%), prioritize the more specific metrics over the more general ones.
These formulas provide rough estimates and don't account for muscle mass, bone density, body composition, or individual variation. For a more complete assessment, also check your BMI and body fat percentage. For the full comparison between different health metrics, read our BMI vs Body Fat guide.