Ideal Weight Calculator - Healthy Range

Medical disclaimer: This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Results are general estimates and may not reflect your individual circumstances. Always consult a qualified healthcare professional before making decisions about your health.

Formula

IBW = 50 + 2.3 × (height(in) - 60) for men

Devine (1974) starts at 50kg for men or 45.5kg for women at 5 feet and adds 2.3kg for every inch above that; Robinson, Miller and Hamwi use the same shape with different constants, which is why they disagree by several kilograms. None of them was derived as a health target: Devine was written for drug dosing, and Hamwi for nutrition assessment. The BMI band of 18.5 to 24.9 is the more useful reference for a healthy adult weight, and it deliberately describes a range rather than one number.

Worked Examples

Example 1: Average Male

Problem:Calculate ideal weight for male, 180cm tall.

Solution:Height in inches = 180 / 2.54 = 70.9 inches Devine: 50 + 2.3 × 10.9 = 75.1 kg Robinson: 52 + 1.9 × 10.9 = 72.7 kg Miller: 56.2 + 1.41 × 10.9 = 71.5 kg Hamwi: 48 + 2.7 × 10.9 = 77.4 kg Average of the four = 74.2 kg BMI Range (18.5-24.9), height 1.80m, 1.80² = 3.24: Min: 18.5 × 3.24 = 60.0 kg Max: 24.9 × 3.24 = 80.7 kg Healthy range: 60-81 kg

Result:About 74 kg by formula, 60-81 kg healthy BMI range

Example 2: Female Example

Problem:Calculate for female, 5'4" (64 inches).

Solution:Height = 64 inches = 162.6 cm Devine Formula: IBW = 45.5 + 2.3 × (64 - 60) IBW = 45.5 + 2.3 × 4 = 54.7 kg = 121 lbs Robinson Formula: IBW = 49 + 1.7 × 4 = 55.8 kg = 123 lbs BMI Range: 18.5 × (1.626)² = 48.9 kg (108 lbs) 24.9 × (1.626)² = 65.8 kg (145 lbs) Healthy range: 108-145 lbs

Result:55 kg (121 lbs) by Devine, 108-145 lbs healthy BMI range

Example 3: Using for Goal Setting

Problem:Person is 170cm, currently 95kg, wants a target weight.

Solution:Height = 170cm = 66.9 inches, 1.70² = 2.89 For a man the four formulas give 65.9, 65.2, 66.0 and 66.7 kg Average ≈ 66 kg BMI healthy range: 18.5 × 2.89 = 53.5 kg 24.9 × 2.89 = 72.0 kg Current: 95 kg Difference to the formula average: 95 - 66 = 29 kg At 0.5kg/week: about 58 weeks At 0.75kg/week: about 39 weeks A nearer first target such as 85 kg (about 10% of body weight, the loss most associated with metabolic benefit) is easier to sustain than aiming straight at the formula figure.

Result:Aim first at roughly 10% loss, then reassess

Frequently Asked Questions

What is ideal body weight?

Ideal body weight (IBW) is an estimated healthy weight based on height and sex. Multiple formulas exist (Devine, Robinson, Miller, Hamwi), each giving slightly different results. These are guidelines, not strict targets. Healthy weight exists within a range, not a single number.

Which ideal weight formula is best?

No single formula is definitively 'best.' Devine is most commonly used in medicine. Robinson and Miller are newer refinements. Hamwi is simpler. For most people, the average of multiple formulas is reasonable. BMI-based ranges (18.5-24.9) provide a healthy weight range rather than a single target.

Why do the formulas give different results?

Each formula was derived from different populations and methods. Devine studied medical dosing, Robinson analyzed insurance data, Miller refined Robinson's work, and Hamwi created rules of thumb for nutrition. The variations are typically 5-10 kg, reflecting that 'ideal' weight is a range, not a precise number.

How is ideal weight used in medicine?

IBW is used for: drug dosing (especially when actual weight is very high or low), ventilator settings, nutritional planning, and as a reference point in clinical assessments. For obesity, adjusted body weight (ABW) may be used rather than actual or ideal weight.

Does ideal weight account for body type?

No. These formulas only use height and sex. They don't account for: bone structure, muscle mass, ethnicity, age, or frame size. A muscular athlete may exceed IBW while being very healthy. Use IBW as one reference point among many health indicators.

Should I aim for my ideal weight?

Not necessarily as an absolute target. Aim for a healthy range based on BMI (18.5-24.9), body composition, how you feel, fitness level, and health markers (blood pressure, cholesterol, blood sugar). Being 5-10 kg above IBW while active and healthy is perfectly fine.

What about frame size?

Some older formulas adjust for small, medium, or large frame (based on wrist or elbow breadth). Modern practice tends to use BMI ranges instead, which inherently allow for variation. If you have a large frame and muscle mass, the upper end of the BMI range is appropriate.

How does age affect ideal weight?

These formulas don't account for age. Some research suggests slightly higher BMI (25-27) may be healthier for those over 65 (the 'obesity paradox'). However, maintaining muscle mass and functional fitness matters more than a specific number as you age.

Can I use ideal weight for goal setting?

Yes, but be flexible. If IBW says 70 kg but you feel great at 75 kg with good fitness and health markers, 75 kg is fine for you. Use IBW as a general guideline, not a rigid target. Focus on sustainable healthy habits rather than a specific number.

What's adjusted body weight for dosing?

For obese patients, some drugs are dosed using Adjusted Body Weight: ABW = IBW + 0.4 × (Actual Weight - IBW). This adjusts for the fact that fat tissue affects drug distribution differently than lean tissue. This is a medical calculation done by healthcare providers.

Background & Theory

Ideal body weight formulas provide estimated healthy weight ranges based on height and sex. They serve as reference points but shouldn't be treated as absolute targets.

Major IBW Formulas:

Devine Formula (1974):

Men: IBW = 50 kg + 2.3 kg × (height(in) - 60)
Women: IBW = 45.5 kg + 2.3 kg × (height(in) - 60)

Robinson Formula (1983):

Men: IBW = 52 kg + 1.9 kg × (height(in) - 60)
Women: IBW = 49 kg + 1.7 kg × (height(in) - 60)

Miller Formula (1983):

Men: IBW = 56.2 kg + 1.41 kg × (height(in) - 60)
Women: IBW = 53.1 kg + 1.36 kg × (height(in) - 60)

Hamwi Formula (1964):

Men: IBW = 48 kg + 2.7 kg × (height(in) - 60)
Women: IBW = 45.5 kg + 2.2 kg × (height(in) - 60)

BMI-Based Healthy Range:

Minimum: 18.5 × height² (m)
Maximum: 24.9 × height² (m)

Frame Size Adjustments:
Some older approaches suggest:

Small frame: -10%
Medium frame: No adjustment
Large frame: +10%

When to Use IBW:

Initial weight loss goal setting
Clinical calculations
General health reference
Nutrition planning

Limitations:

Doesn't account for muscle mass
May not suit all ethnicities
Ignores body composition
One number, not a range

Better Approach:
Use IBW formulas as one data point alongside BMI, body composition, fitness level, and how you feel.

History

Ideal body weight formulas emerged in the mid-20th century as medicine needed standardized reference points for clinical decisions. Early insurance companies' height-weight tables were the first attempts, but lacked scientific basis. Dr. B.J. Devine published his formula in 1974 while researching drug dosing in obese patients. He needed a way to estimate appropriate dosing weight. The Devine formula became the most widely used in clinical practice. Hamwi's formula (1964) was developed for nutrition assessment and is simpler, using whole number multipliers. Robinson (1983) and Miller (1983) refined Devine's work with different population data. The formulas have limitations - they were derived from predominantly Caucasian populations and don't account for ethnic variations in body composition. Asian populations may have health risks at lower BMIs, while Pacific Islanders may be healthy at higher weights. Modern approaches favor BMI ranges (18.5-24.9) over single ideal numbers, recognizing that healthy weight exists within a range. Body composition, fitness, and health markers matter more than hitting a specific number on the scale.