Ideal Body Weight Calculator
Compute ideal body weight (IBW) using the Devine formula, the clinical standard for drug dosing, mechanical ventilation, and nutrition assessment. IBW (men) = 50 + 2.3·(H−60), IBW (women) = 45.5 + 2.3·(H−60). Compare with adjusted body weight (ABW), lean body weight (LBW), and BMI-based healthy weight ranges.
IBW is for dosing, not aesthetics
The Devine formula was originally derived in 1974 for drug dosing — specifically for gentamicin — and remains the clinical standard for dosing many medications, especially those distributed primarily to lean tissue (aminoglycosides, vancomycin loading, heparin). IBW is also used as the reference weight for mechanical ventilation tidal volume (6–8 mL/kg IBW), nutritional assessment, and anesthesia dosing. It describes a healthy reference weight for a given height, not a personal target or aesthetic ideal.
Multiple formulas exist for a reason
Several IBW formulas are in clinical use: Devine (1974), Robinson (1983), Miller (1983), Hamwi (1964), and BMI-based ranges. They differ by a few kilograms at typical adult heights, and no single formula is universally "correct." Devine tends to give slightly higher values for tall men and slightly lower for tall women. The choice of formula depends on the clinical application and local protocol. What matters is consistency — use the same formula within a given protocol.
Percent IBW classifies weight status
The ratio W/IBW × 100% is used to classify weight status in clinical nutrition: <70% indicates severe malnutrition, 70–80% moderate malnutrition, 80–90% mild malnutrition, 90–110% healthy weight, 110–120% overweight, and >120% obese. Percent IBW is preferred over BMI in some clinical settings because it responds linearly to weight change and is easy to explain to patients. Note that percent IBW is not the same as percent of usual body weight or percent weight loss — these are distinct clinical metrics.
ABW and LBW extend IBW clinically
In obese patients, dosing by IBW can under-dose, and dosing by actual weight can overdose. Two derived weights bridge the gap: Adjusted Body Weight (ABW = IBW + 0.4 × (Actual − IBW)) is used for certain drugs distributed to both lean and fat tissue, and Lean Body Weight (LBW = 9270 × W / (6680 + 216 × BMI) for men) estimates fat-free mass directly. Advanced mode computes both, plus the BMI and BMI-based healthy weight range for context.
How to Use This Calculator
The Devine formula links height above 5 feet to a healthy reference weight. Choose sex, then enter height and actual weight to see IBW and weight status.
1. Select biological sex
The Devine formula uses different baselines for men (50 kg) and women (45.5 kg). Choose the option matching the patient's sex for the correct IBW.
2. Choose what to solve for
Usually solve for IBW. You can also solve for the height that would give a target IBW, or solve for actual weight at a target percent-IBW ratio.
3. Enter height in inches
The Devine formula uses inches above 60 inches (5 feet). Presets cover 60–76 inches. Hints show the equivalent in cm and feet/inches.
4. Enter actual weight in kg
The current measured weight is used to compute Percent IBW, weight status category, and — in Advanced mode — adjusted body weight and lean body weight.
5. Read the result and verdict
The result card shows IBW in kg, with the verdict badge classifying weight status (underweight, healthy, overweight, obese) based on Percent IBW.
6. Switch to Advanced for depth
Advanced mode adds an IBW vs. height chart for both sexes, a sensitivity check on a +1% input change, and companion metrics including ABW, LBW, BMI, and BMI-based healthy weight range.
What This Tool Offers
Built around the Devine formula, the most widely used clinical standard for estimating ideal body weight in adults.
Sex-specific Devine formula
Uses the correct baseline (50 kg men, 45.5 kg women) and slope (2.3 kg per inch above 5 feet) for accurate IBW.
Live height-weight schematic
A visual with the height ruler, body silhouette, weight scale, and IBW marker scaled to your inputs.
Weight-status verdict
Percent IBW classified from severe malnutrition through healthy, overweight, and obese with a colour-coded badge.
Companion weight metrics
Adjusted body weight (ABW), lean body weight (LBW), BMI, BMI-based healthy weight range, and weight change needed to reach the healthy range.
Dual comparison charts
Weight-status chart showing your weight relative to IBW, plus an advanced IBW vs. height chart for both sexes.
Reference tables
Comparison of Devine, Robinson, Miller, and Hamwi formulas, plus a weight-status classification table based on percent IBW.
Reference Tables & Conversions
IBW formula comparison, percent-IBW interpretation, and clinical weight metrics.
Percent IBW interpretation
IBW Formula Comparison at 70 inches (5 ft 10 in)
Different IBW formulas give slightly different results for the same height. All values in kg.
| Formula | Year | Men (70 in) | Women (70 in) | Notes |
|---|
IBW Values by Height and Sex (Devine)
Reference table showing Devine IBW in kg and lb for common adult heights.
| Height | cm | IBW Men (kg) | IBW Men (lb) | IBW Women (kg) | IBW Women (lb) |
|---|---|---|---|---|---|
| 5 ft 0 in (60 in) | 152.4 | 50.0 | 110.2 | 45.5 | 100.3 |
| 5 ft 2 in (62 in) | 157.5 | 54.6 | 120.4 | 50.1 | 110.5 |
| 5 ft 4 in (64 in) | 162.6 | 59.2 | 130.5 | 54.7 | 120.6 |
| 5 ft 6 in (66 in) | 167.6 | 63.8 | 140.7 | 59.3 | 130.7 |
| 5 ft 8 in (68 in) | 172.7 | 68.4 | 150.8 | 63.9 | 140.9 |
| 5 ft 10 in (70 in) | 177.8 | 73.0 | 160.9 | 68.5 | 151.0 |
| 6 ft 0 in (72 in) | 182.9 | 77.6 | 171.1 | 73.1 | 161.2 |
| 6 ft 2 in (74 in) | 188.0 | 82.2 | 181.2 | 77.7 | 171.3 |
| 6 ft 4 in (76 in) | 193.0 | 86.8 | 191.4 | 82.3 | 181.4 |
Variable Reference
| Symbol | Meaning | Typical range | Units |
|---|---|---|---|
| IBW | Ideal body weight | 40 – 90 | kg |
| H | Height | 58 – 78 | inches |
| W | Actual weight | 40 – 200 | kg |
| ABW | Adjusted body weight | IBW + 0.4 × (W − IBW) | kg |
| LBW | Lean body weight | 9270 × W / (6680 + 216 × BMI) | kg |
| %IBW | Percent of ideal body weight | 70 – 150% | % |
| BMI | Body mass index | 15 – 45 | kg/m² |
What Does the Devine IBW Formula Measure?
The Devine formula estimates a healthy reference body weight for a given height and sex. It was published in 1974 by Dr. B.J. Devine as part of a study on gentamicin dosing and has since become the most widely used clinical standard for ideal body weight in adult medicine. The formula anchors a baseline weight at 5 feet (50 kg for men, 45.5 kg for women) and adds 2.3 kg for each inch of height above 5 feet. The result is a single number that represents a healthy reference weight, used clinically for drug dosing, mechanical ventilation, nutritional assessment, and as a comparison point for actual body weight.
Devine IBW Formula
The defining relationships are:
IBW (women) = 45.5 + 2.3 × (H − 60)
where H is height in inches. Rearranged to solve for the other quantities:
Percent IBW = (Actual Weight / IBW) × 100
Adjusted body weight (used in obesity for certain drugs):
Lean body weight (Janmahasatian, 2005):
LBW (women) = 9270 × W / (8780 + 244 × BMI)
Devine IBW Variables
| Symbol | Meaning | Notes |
|---|---|---|
| IBW | Ideal body weight | Healthy reference weight in kg |
| H | Height | In inches, above 60 in (5 ft) |
| W | Actual weight | Current measured weight in kg |
| ABW | Adjusted body weight | IBW + 0.4 × (W − IBW) |
| LBW | Lean body weight | Estimates fat-free mass from W and BMI |
| %IBW | Percent of IBW | (W / IBW) × 100; classifies weight status |
How Each Variable Affects IBW
IBW increases linearly with height above 5 feet: each additional inch adds 2.3 kg for both men and women. The only sex difference is the baseline at 5 feet — 50 kg for men, 45.5 kg for women. Below 5 feet, the formula continues to decrease linearly, though it is less clinically validated at very short heights. In practice, most adult patients fall between 60 and 78 inches (152–198 cm), where the formula is well established.
IBW is not a target weight for individuals and does not account for frame size, muscle mass, age, or ethnicity. A muscular athlete may weigh significantly more than IBW while having low body fat; an elderly person may weigh less than IBW due to loss of muscle mass. In these cases, IBW should be interpreted alongside other metrics: BMI, percent body fat, waist circumference, and clinical assessment. IBW's primary value is as a standardizing reference for clinical dosing and nutrition calculations, not as a personal weight goal.
IBW Calculation Examples
IBW = 50 + 2.3 × (70 − 60) = 50 + 2.3 × 10 = 50 + 23 = 73.0 kg = 160.9 lb
IBW = 45.5 + 2.3 × (70 − 60) = 45.5 + 23 = 68.5 kg = 151.0 lb
IBW = 73.0 kg
Percent IBW = (75 / 73.0) × 100 = 102.7% (healthy range)
IBW = 73.0 kg
ABW = 73.0 + 0.4 × (90 − 73.0) = 73.0 + 6.8 = 79.8 kg
Used for dosing certain drugs in obese patients.
Frequently Asked Questions
Many drugs distribute primarily to lean tissue rather than fat. If you dose by total body weight in an obese patient, you may overdose the lean tissue; if you dose by IBW, you may under-dose the actual lean mass, which is larger than IBW predicts. The Devine formula was specifically derived for gentamicin dosing and became the clinical standard because it provides a consistent, reproducible reference weight that correlates reasonably well with lean body mass in normal-weight patients. For obese patients, adjusted body weight (ABW) or lean body weight (LBW) is often used instead.
No. IBW is a clinical reference weight used for dosing and standardization, not a personal weight goal. It does not account for frame size, muscle mass, age, or body composition. A healthy weight for any individual depends on their specific body composition, medical history, and lifestyle. The BMI-based healthy weight range (18.5–24.9 kg/m²) is another reference that captures a range rather than a single number. For personal weight goals, work with a clinician or registered dietitian who can consider the full picture.
No single formula is universally most accurate — they were derived from different populations using different methods. Devine (1974) tends to give slightly higher values for men and slightly lower for women compared to Robinson (1983). Miller (1983) gives lower values for tall individuals. Hamwi (1964) is the oldest and still used for some clinical purposes. The choice depends on institutional protocol and clinical application. What matters most is consistency: use the same formula across a treatment protocol so that doses are comparable.
Adjusted body weight (ABW = IBW + 0.4 × (Actual − IBW)) is used for drugs that distribute partially to fat tissue but primarily to lean tissue, and for which dosing by IBW would under-dose and dosing by actual weight would overdose. Common examples include aminoglycosides in obese patients, certain anticoagulants, and some chemotherapy agents. For drugs that distribute entirely to lean tissue (e.g., heparin loading), IBW alone is often preferred. For drugs that distribute widely to fat (e.g., lipophilic anesthetics), actual body weight may be appropriate. Always consult drug-specific guidelines.
In mechanical ventilation, tidal volume is set based on predicted body weight (PBW), which is essentially IBW computed by the ARDSNet formula (a variant of Devine). The standard is 6–8 mL/kg PBW for lung-protective ventilation. Using PBW rather than actual weight prevents over-distension of the lungs in obese patients — the lungs do not scale with body fat, so tidal volume should reflect lean body size. This is one of the most important uses of IBW in critical care and is proven to reduce mortality in acute respiratory distress syndrome (ARDS).
The original Devine formula was derived primarily from Caucasian populations, and there is evidence that IBW values differ across ethnic groups due to differences in body composition and frame size. Some studies have proposed adjusted formulas for specific populations, but no single ethnicity-adjusted formula has achieved universal acceptance. In practice, IBW remains widely used across populations because its primary clinical applications (drug dosing, ventilation) benefit more from a consistent reference than from a highly population-specific one. Clinicians should be aware that IBW may slightly overestimate or underestimate lean mass in different populations.
No. The Devine formula and other adult IBW formulas are not appropriate for children, whose growth and body composition change rapidly with age. Pediatric dosing uses weight-based calculations (mg/kg) with actual body weight up to a certain threshold, or body surface area (BSA) for certain drugs. Pediatric IBW formulas exist but are less standardized and less used than in adults. For children, always use pediatric-specific dosing references and consult a pediatric pharmacist or clinician.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| IBW | Ideal body weight | kg |
| height_in | Height | inches |
What it means
The Devine formula estimates ideal body weight (IBW) based on height and sex. It was originally developed for drug dosing (e.g., for renal function estimation, anaesthesia). For men: 50 kg for 5 feet (60 inches) plus 2.3 kg per additional inch. For women: 45.5 kg for 5 feet plus 2.3 kg per additional inch. It is used in clinical nutrition, for ventilator settings, and in pharmacology to adjust doses. While it provides a reference, it does not account for muscle mass or body composition. Understanding IBW is useful for clinicians to estimate dosages and to set weight goals in obesity management.
Worked example
Ideal Body Weight (Devine) – Two Detailed Examples
Real‑World| Parameter | Value |
|---|---|
| Sex | Men |
| height (in) | 70 |
| Parameter | Value |
|---|---|
| Sex | Women |
| height (in) | 65 |
Common mistakes
- Devine formula: For men: 50 + 2.3 × (height_in − 60); for women: 45.5 + 2.3 × (height_in − 60).
- Height in inches: Not centimetres – convert if necessary.
- IBW: Ideal body weight – used for medication dosing and nutritional assessment.
- Limitations: Does not account for frame size or muscle mass – use with caution.
- Alternative formulas: Other formulas exist (Hamwi, Robinson) – choose the appropriate one.
Applications
The Devine formula provides estimates of ideal body weight (IBW) based on height and sex, commonly used in clinical settings for drug dosing and nutritional assessment. It is also used to set weight goals in weight management programmes. Healthcare professionals, such as physicians, dietitians, and pharmacists, use IBW to calculate appropriate medication doses, to assess nutritional status, and to guide weight recommendations. While it does not account for body composition, it is a quick and useful reference. By using IBW, clinicians can standardise dosage and monitor patient progress. Understanding IBW helps in the personalised management of obesity and related conditions.
- Drug dosage calculations (e.g., chemotherapy, anaesthesia)
- Nutritional assessment and diet planning
- Weight goal setting in obesity and eating disorders
- Clinical research and patient stratification
- Health promotion and lifestyle counselling
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