How is ideal body weight calculated?

The most common formulas are Devine (for medication dosing), Hamwi (clinical nutrition), Robinson, and Miller — all based on height. A healthy BMI range (18.5–24.9) provides a realistic weight window rather than a single number.

Is there one ideal weight for my height?

No — different formulas give different results, and healthy weight varies with body frame and muscle mass. Most people fall within a range of 10–20 lbs depending on the formula used.

What weight should I aim for?

Rather than a single number, aim for the overlapping range across multiple formulas. This accounts for individual differences in bone density, muscle mass, and body frame size.

🎯 Ideal Weight Calculator

Compare four clinical formulas (Devine, Hamwi, Robinson, Miller) alongside the healthy BMI range for your height. Ideal weight is presented as a realistic range — not an arbitrary single number.

What is ideal body weight?

Ideal body weight (IBW) formulas were originally developed in the 1960s–80s for calculating medical drug dosages — not as aesthetic targets. They all share the same basic format: a base weight at 5 feet of height, plus an increment for each additional inch.

The Devine formula (1974) is the most commonly used in clinical settings. The BMI-based healthy range (18.5–24.9) is generally a more useful practical guide, as it produces a range rather than a single point.

Limitations to know

All four formulas consider only height and sex — not muscle mass, bone density, age, or fitness level. A trained athlete can be significantly heavier than any formula's result while being in excellent health. Think of these numbers as a starting reference point, not a prescriptive target.

What Is "Ideal Weight"?

The concept of an "ideal body weight" originated in the insurance industry in the mid-20th century, when actuaries noticed that mortality rates varied with body weight. The original formulas were developed to predict life expectancy for insurance purposes, not as medical guidance — a distinction worth keeping in mind when interpreting your result.

Today, ideal weight formulas serve as rough reference points rather than precise targets. Your healthiest weight depends on your body composition, muscle mass, bone density, age, sex, and genetics — factors that simple height-based formulas cannot capture. That said, these formulas provide a useful starting point for conversations about health goals.

The Four Formulas

This calculator shows four different ideal weight estimates, each from a different formula. They were all designed for adults and use height as the primary input, but differ in their underlying data sources and constants.

Devine Formula (1974)

Originally created for pharmaceutical dosing calculations (specifically digoxin dosing), the Devine formula became the most widely cited ideal weight formula in clinical medicine despite never being validated for weight management. It remains the standard in many hospital settings.

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

Robinson Formula (1983)

The Robinson formula was a revision of Devine, based on medium-frame data from the Metropolitan Life Insurance tables. It produces slightly lower estimates than Devine, particularly for taller individuals.

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

Miller Formula (1983)

Also based on Metropolitan Life data, the Miller formula produces the lowest estimates of the four and is considered by some to be the most conservative. It's less commonly used in clinical settings than Devine but is included here for completeness.

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

Hamwi Formula (1964)

The Hamwi formula was developed for estimating caloric needs in hospitalised patients. It uses a larger per-inch increment than the others and tends to produce higher estimates, particularly for taller individuals. It also optionally adjusts for small, medium, or large body frame.

Men: IBW = 48 kg + 2.7 kg × (height in inches − 60)
Women: IBW = 45.4 kg + 2.3 kg × (height in inches − 60)

How the Formulas Compare

For a woman who is 165 cm (5'5") tall, the four formulas give:

Formula	Estimate for 5'5" Woman
Devine	56.1 kg (123.7 lbs)
Robinson	53.6 kg (118.1 lbs)
Miller	60.5 kg (133.4 lbs)
Hamwi	56.8 kg (125.2 lbs)

The spread between the lowest and highest estimates is over 7 kg for the same person. This illustrates why treating any single formula as a definitive target is misguided — use the range as a reference zone, not a fixed goal.

Limitations of Ideal Weight Formulas

All four formulas share the same fundamental limitation: they only use height. They cannot account for:

Muscle mass: A well-trained athlete will have a significantly higher healthy weight than these formulas suggest.
Bone density: People with denser bones naturally weigh more at the same height.
Age: As we age, body composition shifts — modest weight gain in older adults is not necessarily unhealthy.
Ethnicity: Body composition varies significantly across ethnic groups at the same height and weight.
Body frame size: A large-framed person will naturally weigh more than a small-framed person of the same height.

A healthier approach: Instead of targeting a specific number, aim for a weight range where your key health markers — blood pressure, blood glucose, cholesterol, energy levels — are in healthy ranges. For many people, this is 5–10% above ideal weight formula estimates.

Ideal Weight vs BMI

Ideal weight formulas and BMI are both height-based tools with similar limitations. The key difference is that BMI gives you a range of healthy weights (BMI 18.5–24.9), whereas ideal weight formulas give a specific point estimate. In practice, a "normal" BMI for a 165 cm woman corresponds to weights of 50–68 kg — a much wider and more realistic range than any single ideal weight formula produces.

For most people, a practical goal is to achieve a BMI in the lower half of the normal range (18.5–22) while maintaining good muscle mass — rather than trying to hit a specific ideal weight formula target.

Setting Realistic Weight Goals

Research consistently shows that modest weight loss — even 5–10% of body weight — produces meaningful improvements in blood pressure, blood sugar, cholesterol, and joint pain in people who are overweight. You do not need to reach an "ideal" weight to substantially improve your health.

Set process goals (eating habits, exercise frequency) rather than purely outcome goals (a specific weight)
Use a rate of 0.5 kg/week as a benchmark — faster rates increase muscle loss risk
Use our Calorie Calculator to determine your daily calorie target
Track body measurements and how your clothes fit — the scale alone misses body recomposition
Consult a registered dietitian or physician for personalised guidance, especially if you have underlying health conditions

Frequently Asked Questions

Which ideal weight formula is most accurate?

None of them is definitively "most accurate" for all people — they were developed in different contexts, from different populations, for different purposes. The Devine formula is the most widely cited in clinical medicine, but this is partly historical convention. The range across all four formulas is more informative than any single estimate.

My ideal weight seems too low. Is something wrong?

These formulas are best for average body types. If you have a larger frame, significant muscle mass, or are an older adult who has lost some height, the estimates may seem unrealistically low. This is a known limitation of all height-only formulas. A BMI of 20–22 for your height is often a more practical target range.

Does ideal weight change with age?

The formulas themselves don't adjust for age, but health guidelines generally acknowledge that modest weight gain in older adults (50+) is not necessarily problematic — and that being too thin in old age carries its own risks (frailty, bone loss, reduced immune function). For older adults, maintaining muscle mass often matters more than total weight.

How is ideal weight different from healthy weight range?

Ideal weight formulas give a single point estimate. A "healthy weight range" — typically defined by BMI 18.5–24.9 — gives a range of weights associated with low health risk. The healthy weight range is broader and generally more appropriate as a real-world target. Most people are metabolically healthy anywhere within the normal BMI range, not just at the specific "ideal" weight point.