Ideal Body Weight Calculator – 4 Science-Based Formulas

Figuring out what you should weigh can feel surprisingly complicated — there's no single "right" number, and different sources often give different answers. This ideal body weight calculator cuts through the confusion by running your height and gender through four of the most well-established medical formulas simultaneously, giving you a consolidated range alongside a healthy BMI weight window.

Whether you're setting a fitness goal, tracking your progress, or simply curious about what health professionals consider a target weight for your frame, this tool gives you a clear, science-backed starting point. In seconds, you'll see results from the Robinson, Miller, Devine, and Hamwi formulas — the same equations used in clinical medicine, nutrition, and exercise science for decades.

Keep in mind that "ideal weight" is a guideline, not a verdict. Your actual healthy weight depends on factors like muscle mass, bone density, and body composition that no height-based calculator can fully measure. But knowing your range is a genuinely useful first step toward informed, realistic health goals.

"Ideal body weight" (IBW) refers to the weight that medical and nutrition professionals have historically associated with good health outcomes for a person of a given height and sex. The concept has been around since the 1960s, when researchers began looking for simple ways to estimate appropriate weight for dosing medications, predicting lung capacity, and guiding clinical decisions.

Over time, four formulas became the standard references in medicine. While each takes a slightly different approach, they all share the same basic logic: start with a baseline weight for a reference height of 5'0", then add a fixed amount for every inch above that baseline.

Today, IBW remains widely used in clinical settings — particularly for calculating medication doses and ventilator settings — as well as in nutrition counseling and fitness planning. It's worth knowing that these formulas were developed primarily for adults, and they don't account for age, muscle mass, or ethnic differences in body composition. Think of them as useful benchmarks rather than absolute targets.

Each formula produces a slightly different result, which is why showing all four gives you a more complete picture than any single estimate could.

Robinson Formula (1983): Developed by J.D. Robinson and colleagues as a refinement of earlier work, this formula tends to produce results in the middle of the range. It's most commonly used in pharmacokinetics for calculating drug doses based on body weight.

Miller Formula (1983): Created by D.R. Miller and team in the same era, this formula generally yields the highest ideal weight estimates of the four — which many practitioners find more realistic for taller individuals or those with larger frames.

Devine Formula (1974): The oldest formula still in regular clinical use, developed by B.J. Devine for internal medicine. It's the formula most widely used in respiratory therapy for calculating tidal volumes in patients on mechanical ventilation.

Hamwi Formula (1964): The original clinical rule of thumb from G.J. Hamwi, developed for estimating caloric needs in diabetic patients. It's the simplest to calculate mentally and remains a common reference in nutrition counseling.

You only need two pieces of information:

1. Select your gender. Choose Male or Female. Each formula uses different baseline weights and per-inch increments for men and women, so this step directly affects your results.
2. Enter your height in inches. If you think in feet and inches, convert first: multiply feet by 12, then add the remaining inches. For example, 5'10" = (5 x 12) + 10 = 70 inches.
3. Read your results. The calculator instantly displays three sections:

• Ideal Weight Range — your consolidated range across all four formulas
• Formula Results — each formula's individual estimate
• BMI Results — the weight range corresponding to a healthy BMI (18.5-24.9)

That's all there is to it. Results update immediately as you adjust your height or gender.

Let's walk through a real example. For a 5'10" (70-inch) male:

Notice that the four formulas produce a spread of about 11 pounds. This range — rather than any one number — is the most useful output. If your current weight falls within or close to the 155-166 lb window, you're in line with what these medical formulas consider optimal for your height.

The healthy BMI range (129-174 lbs in this example) is intentionally wider. It represents the full healthy-weight window from BMI 18.5 to 24.9, giving you a broader frame of reference.

For a 5'5" (65-inch) female, the results look like:

• Robinson: ~124 lbs | Miller: ~127 lbs | Devine: ~120 lbs | Hamwi: ~125 lbs
• Ideal Weight Range: ~120-127 lbs

You'll notice the calculator shows two different ranges. They're related, but not the same.

IBW formulas produce a specific target based on height and gender. They're precise by design — clinical applications like medication dosing and ventilator settings need a single reference number to work from.

Healthy BMI range is broader because BMI defines "healthy" as any weight between 18.5 and 24.9 across a wide spectrum. For most people, the IBW formulas cluster toward the middle or lower-middle of the healthy BMI range.

Neither measurement accounts for body composition. A 5'10" male at 190 lbs who does significant strength training may be in excellent health despite being above the IBW range. Meanwhile, someone at "ideal" weight with high body fat might carry real health risks. These numbers are reference points, not diagnoses.

The fact that four well-established medical formulas produce different results for the same person isn't a flaw — it's an honest reflection of how complex human bodies are. No single number can be definitively "correct" for everyone of a given height.

Your actual healthy weight depends on several factors these formulas can't see:

• Muscle mass: Muscle is denser than fat. A very fit person may weigh more than the IBW range while being in excellent health.
• Bone density: People with naturally denser bones weigh more, independent of fat or muscle.
• Frame size: The formulas don't distinguish small, medium, and large body frames. Some clinicians apply a +/-10% adjustment for frame size.
• Age: As people age, body composition changes. Older adults may actually maintain better health outcomes at slightly higher weights than these formulas suggest.
• Ethnicity: Body composition varies across ethnic groups in ways that height-based formulas don't capture.

The range from this calculator is a well-validated, evidence-based starting point. For personalized weight goals — especially if you're managing a health condition — your doctor or a registered dietitian can account for your full picture.

Which ideal weight formula is the most accurate? No single formula is definitively most accurate for everyone — they were each developed for specific clinical contexts. Robinson and Devine are most common in pharmacology and respiratory medicine, while Hamwi is widely used in nutrition counseling. The consensus range across all four is generally more meaningful than any individual result.

Why do the four formulas give different results? They were developed by different researchers at different times, using different patient populations and clinical goals. Robinson and Miller (both 1983) tend to cluster closer together. Devine (1974) often runs lower for shorter individuals, while Hamwi (1964) tends toward the higher end. For most heights, the spread is around 10-15 lbs.

Does age affect my ideal weight? These formulas don't factor in age. Research suggests, however, that adults over 65 may benefit from maintaining slightly higher weights to preserve muscle mass and reduce frailty risk — a consideration the standard IBW formulas don't reflect. Your healthcare provider can help you set age-appropriate targets.

What if I'm very muscular? IBW formulas will likely underestimate a healthy weight for people with above-average muscle mass. A competitive athlete or regular strength trainer might weigh 10-30 lbs more than the IBW range while being completely healthy. In these cases, body fat percentage is a more useful metric than weight alone.

How is ideal weight different from BMI? BMI uses both your height and current weight to calculate a score, telling you where you fall in a weight classification (underweight, healthy, overweight, obese). IBW formulas output a target weight based on height alone. They're complementary — BMI tells you where you are, IBW gives you a reference point for where you might aim.

Should I try to hit the middle of the ideal weight range? Not necessarily. The range represents reasonable targets based on different validated formulas. Some people naturally and healthily sit at the lower end; others at the upper end. Rather than fixating on a specific number, consider your energy levels, how you feel day to day, and what your doctor says about your overall health markers.

Is ideal body weight the same as a weight loss goal? Not exactly. IBW is a clinical reference point. A personalized weight loss target should factor in your starting weight, health conditions, rate of sustainable loss, and realistic lifestyle goals. Your IBW range can serve as a useful long-term reference, but working with a healthcare professional to set intermediate milestones is a smarter approach than aiming straight for IBW.

Can I use this calculator for children or teenagers? No. IBW formulas are validated for adults only and should not be applied to children or adolescents. For younger people, pediatric BMI-for-age charts (like those from the CDC) are the appropriate reference tool.

What if I'm currently above the ideal weight range? Good news: even modest weight loss produces real health benefits. Research consistently shows that losing just 5-10% of body weight can meaningfully reduce blood pressure, improve blood sugar control, and lower cardiovascular risk — even if your weight never reaches the ideal range. Small, sustainable progress matters far more than hitting a specific number.

The formulas in this calculator are established medical references, but they have real limitations. They were developed primarily using data from white adult populations, and they don't account for body composition, frame size, fitness level, age, or ethnicity. For most healthy adults, they provide a reasonable ballpark — but they were originally designed for clinical applications like drug dosing, not personal fitness targets.

Use this calculator as an informational starting point. For personalized guidance on achieving and maintaining a healthy weight, speak with your doctor, a registered dietitian, or a certified fitness professional who can evaluate your complete health picture.

For those interested in the underlying math, here are the complete equations (height in inches, weight in pounds):

Robinson Formula (1983):

• Male: 114 lbs + 4.2 lbs x (height in inches - 60)
• Female: 108 lbs + 3.7 lbs x (height in inches - 60)

Miller Formula (1983):

• Male: 124 lbs + 3.1 lbs x (height in inches - 60)
• Female: 117 lbs + 3.0 lbs x (height in inches - 60)

Devine Formula (1974):

• Male: 110 lbs + 5.1 lbs x (height in inches - 60)
• Female: 100 lbs + 5.1 lbs x (height in inches - 60)

Hamwi Formula (1964):

• Male: 106 lbs + 6.0 lbs x (height in inches - 60)
• Female: 100 lbs + 5.0 lbs x (height in inches - 60)

These formulas apply to adults who are at least 5'0" (60 inches) tall. For heights below 5'0", clinical practice typically uses a modified approach — subtracting the per-inch increment for each inch below 5'0" rather than adding it.