Ideal Body Weight Calculator: How to Find Your Healthy Weight

Anyone who has typed “ideal body weight calculator” into a search engine has probably noticed that different websites give different numbers. That’s because there isn’t one magic formula — there are at least five common ones, each created for a different medical purpose, and we’ll compare the major formulas, explain how healthy weight ranges actually work, and help you make sense of the numbers that matter for your health.

Most cited clinical formula for IBW: Devine formula (1974) · Minimum healthy BMI: 18.5 · Maximum healthy BMI: 24.9 · U.S. adults overweight or obese: 73.6%

1. Measure your height in inches (or centimeters).
2. Choose a formula — the Devine formula is most common in hospitals.
3. For men, calculate: 50 kg + 2.3 kg for each inch over 5 feet. For women: 45.5 kg + 2.3 kg per inch over 5 feet.
4. Alternatively, use the universal equation: Wt (lb) = 5 × BMI + (BMI ÷ 5) × (Ht − 60 in) with a target BMI.
5. Compare your calculated IBW to the healthy BMI range of 18.5–24.9.

The table below shows the core measurements and formulas for quick reference.

How do you calculate ideal body weight?

Devine formula for men and women

The most widely used formula in U.S. hospitals is the Devine formula, developed in 1974 for drug dosing. According to the CDC – U.S. public health agency CDC – U.S. public health agency, the formula for men is: 50 kg + 2.3 kg per inch over 5 feet. For women: 45.5 kg + 2.3 kg per inch over 5 feet. The same numbers are echoed by ClinCalc – medical reference tool and Healthline – medical editorial site.

Robinson, Miller, and Hamwi formulas

Three other formulas — Robinson (1983), Miller (1985), and Hamwi (1964) — offer slightly different base weights and incremental adjustments. While the exact equations vary, all were developed for similar clinical purposes. The Robinson formula starts at 52 kg for men and 49 kg for women, the Miller at 56.2 kg and 53.1 kg, and the Hamwi at 48 kg and 45.5 kg, each with different per-inch additions. These differences can shift the calculated IBW by several kilograms, especially for taller individuals.

The universal equation

A more modern approach comes from a peer-reviewed review published in PMC – peer-reviewed medical journal. It provides a universal equation that can estimate ideal body weight for any target BMI. In U.S. units: Wt (lb) = 5 × BMI + (BMI ÷ 5) × (Ht − 60 in). In metric: Wt (kg) = 2.2 × BMI + 3.5 × BMI × (Ht − 1.5 m). This flexibility makes it useful for both clinical and wellness settings.

The implication: The formula you choose changes your “ideal” number, but the BMI range remains the gold standard for health screening.

What is a healthy weight for my height?

BMI weight ranges for adults

The UVA Health – university medical center states that a healthy weight range corresponds to a BMI of 18.5 to 24.9. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese. The Calculator.net – online reference tool confirms the same WHO-recommended range for both males and females.

BMI limitations for older adults and athletes

Importantly, BMI does not distinguish between muscle and fat. Healthline – medical editorial site points out that ideal body weight formulas may estimate the weight with lowest mortality risk, but they don’t account for individual body composition. For older adults, a slightly higher BMI may be protective, though specific numbers vary by study.

What this means: BMI is a useful starting point, but it’s not a diagnostic tool for individuals.

What is the IBW formula?

Why the Devine formula is most common in hospitals

Originally developed by Dr. Devine in 1974 to dose gentamicin, the formula quickly became the default for drug dosing, anesthesia, and nutritional assessment. According to ClinCalc – medical reference tool, it remains the standard because it is simple, reproducible, and well-studied in clinical populations.

Adjusted body weight formula for obese patients

For patients who are significantly above IBW, clinicians often calculate adjusted body weight. The formula is: Adjusted body weight = IBW + 0.4 × (actual weight − IBW). This is used especially for ventilated patients and those in critical care, where accurate drug dosing is critical. The PMC – peer-reviewed medical journal review discusses the use of IBW in nutritional and pharmacological management.

The catch: IBW formulas were not designed for weight management but for clinical dosing, so be cautious when using them for personal goals.

How much should I weigh for my height and age?

Weight ranges for older women (age 65+)

For a 5’4″ woman over 65, a healthy weight typically falls between 110 and 145 pounds (50–66 kg). Some research suggests that a BMI between 24 and 27 may be protective for older adults, though this is not a universal guideline. The CDC – U.S. public health agency notes that there is no consensus on IBW methods for children, and similarly, age-specific adjustments for adults remain an area of research.

Weight ranges for men over 70

For men over 70, maintaining adequate muscle mass becomes as important as the number on the scale. A healthy BMI range of 22–27 is often recommended, though individual health status matters more than a fixed number. The goal should be to maintain strength and functional ability, not simply to achieve a target weight.

The pattern: For older adults, the scale is less important than muscle mass and functional ability.

What is the ideal weight for an older woman?

Weight chart for senior women

For a 5’4″ woman over 65, the approximate healthy range is 110–145 lb (50–66 kg). The lower end corresponds to a BMI of about 19, the upper end to a BMI of 25. Going slightly above that range may be acceptable if muscle mass is good and metabolic health is stable.

When to consult a doctor

If you are losing weight without trying, or if your weight has changed rapidly, it is important to see a healthcare professional. The UVA Health – university medical center encourages using the BMI-based healthy range as a screening tool, followed by a conversation with a doctor or dietitian to set individual goals.

“The use of IBW formulas in nutritional assessment is well established, but they are not diagnostic of health. They serve as a reference point, not a prescription.”

PMC – peer-reviewed medical journal

“A BMI between 18.5 and 24.9 is associated with the lowest risk of chronic disease for most adults.”

UVA Health – university medical center

“The Devine formula remains the most commonly used IBW calculation in clinical practice because it is simple, free, and has historical precedent.”

ClinCalc – medical reference tool

There is no universal “ideal” weight. The right number depends on why you’re asking. For a doctor dosing a medication, the Devine formula is the standard. For someone managing their general health, the healthy BMI range of 18.5–24.9 is a better guide. And for older adults, maintaining muscle and functional ability matters more than hitting a specific weight. For anyone using an ideal body weight calculator, the real takeaway is this: use the tool as a starting point, then talk to a professional who can factor in your individual health, age, and activity level.

While the calculator above gives you a quick estimate, you can also explore detailed guidelines on ideal weight for height and age to see how the numbers align with clinical recommendations.

Frequently asked questions