Ideal Weight Calculator

Ideal Weight Calculator — Devine, Robinson, Miller and Hamwi Formulas

Ideal body weight (IBW) formulas estimate a target weight based on height and sex. Unlike BMI, which tells you whether your current weight falls within a healthy range, IBW formulas give you a single-number target — a weight that researchers and clinicians have historically associated with optimal health outcomes for a given height. This calculator implements all four major formulas and compares them side by side, giving you a clearer picture than any single formula alone.

The four formulas in this calculator are the Devine formula (1974), the Robinson formula (1983), the Miller formula (1983), and the Hamwi formula (1964). They were each derived from different population datasets and use slightly different coefficients, which is why they give different results for the same height. The calculator also shows the WHO BMI-based healthy weight range (18.5–24.9), which is wider than any single IBW value and represents the full healthy spectrum.

What is Ideal Body Weight?

Ideal body weight is a clinical construct — a weight estimate derived from population data that represents the statistically optimal weight for a given height and sex. The term was coined in the context of drug dosing: pharmacologists needed a way to calculate medication doses that accounted for body size without being distorted by excess fat mass. The Devine formula, the most widely used IBW formula today, was originally published in a paper about creatinine clearance estimation, not as a fitness target.

Over time, IBW formulas were adopted more broadly as reference points for weight management. They are now used in clinical nutrition assessment, respiratory therapy (tidal volume calculations in mechanical ventilation use IBW to avoid lung injury in obese patients), sports science, and general health guidance. The formulas are not perfect — they assume a fixed relationship between height and healthy weight that does not account for muscle mass, bone density, age, or ethnic variation — but they remain useful benchmarks.

It is important to understand that IBW is a target or reference value, not a hard rule. The WHO healthy weight range (BMI 18.5–24.9) encompasses a range of weights, and any point within that range is associated with good health outcomes. You do not need to hit an exact IBW formula number. For most people, the average of the four formula results falls near the middle of the BMI healthy range, making it a reasonable aspirational target.

The Four Ideal Weight Formulas

Each formula calculates IBW as a base weight for a person exactly 5 feet (152.4 cm) tall, plus an increment per inch above 5 feet. The base weight and increment differ by formula and sex.

Devine (1974) is the oldest of the modern four and the most widely cited. It was published by Dr. B.J. Devine in the context of predicting creatinine clearance in patients. Despite being a pharmacokinetic tool rather than a body composition target, it became the dominant IBW formula in Western clinical practice. Most electronic health record systems that calculate IBW use the Devine formula.

Robinson (1983) was published by J.D. Robinson and colleagues as a revision of Devine intended to better fit population data. The male base weight (52 kg vs. Devine's 50 kg) is slightly higher, but the per-inch increment (1.9 vs. 2.3) is lower, making Robinson give lower IBW estimates for tall men compared to Devine. For women, the Robinson formula gives higher base weight (49 vs. 45.5 kg) but the same lower increment pattern.

Miller (1983) was published the same year as Robinson and takes a different approach — a higher base weight (56.2 kg for men, 53.1 kg for women) with a smaller per-inch increment (1.41/1.36). This means Miller gives the highest IBW estimates for people of average height and the lowest for very tall people. Miller IBW is used in some respiratory therapy protocols.

Hamwi (1964) is the oldest formula of the four, predating all others by a decade. Dr. George Hamwi published it as a simple clinical rule of thumb for dietitians. It uses round numbers: 106 lbs (48 kg) for men at 5 feet, +6 lbs per additional inch; 100 lbs (45.5 kg) for women, +5 lbs per additional inch. The simplicity made it easy to teach and use without a calculator, which accounts for its longevity in clinical education.

BMI-Based Healthy Weight Range vs. IBW Formulas

The WHO healthy weight range (BMI 18.5–24.9) is calculated differently from IBW formulas. Rather than targeting a single value, it defines the full range of weights that correspond to a healthy BMI for a given height. The formula is: Weight = BMI × height² (in meters). This produces a range — for a 175 cm person, the healthy range is 56.7–76.3 kg — that is substantially wider than any single IBW formula result.

In practice, the average of the four IBW formulas typically falls near the lower third of the BMI healthy range. For a 175 cm man, the formula average is approximately 67–70 kg, while the BMI healthy range extends up to 76 kg. This means a person at the high end of healthy BMI (say, BMI 24 at 175 cm = 73.5 kg) is technically above all four IBW formula results but still within a clinically healthy range. Use both the IBW formula average and the BMI range together — neither is the complete picture.

Ideal Weight by Height — Quick Reference

The tables below show IBW estimates for common heights. All weights shown in kilograms. The Average column is the mean of the four formulas.

Men

Women

Limitations of Ideal Weight Formulas

IBW formulas have significant limitations that matter in practice:

• No muscle mass adjustment. The formulas treat everyone of the same height and sex as identical. A trained athlete with 75 kg of lean mass will be flagged as overweight by IBW formulas even at 6–8% body fat. For muscular individuals, the Body Fat Calculator is a more meaningful metric than IBW.
• No age adjustment. Body composition changes with age — older adults naturally lose lean mass and gain fat. A 65-year-old and a 25-year-old of the same height may have identical IBW results but very different health risk profiles. The formulas were derived primarily from young-to-middle-aged adult populations.
• No ethnic variation. Research shows that South and East Asian populations have higher body fat percentages and cardiovascular risk at BMIs where European populations are in the normal range. IBW formulas do not address this. Some health authorities use lower BMI thresholds for Asian populations.
• No frame size adjustment. People with naturally larger or smaller skeletal frames carry proportionally more or less lean mass. Some clinicians use a wrist circumference measurement to classify frame as small, medium, or large, then adjust IBW by ±10%. The formulas here use no frame adjustment.
• Designed for moderate height range. All four formulas were derived from population data centered around 5'0"–6'2" (152–188 cm). Results become less reliable at heights outside this range, particularly for very short individuals where the base weight dominates and for very tall people where linear extrapolation may overestimate.

How to Use This Calculator Effectively

The most useful output from this calculator is not any single formula result but the interplay between three data points: (1) the BMI healthy range, (2) the formula average, and (3) your current BMI if you enter your weight. Together, these tell a complete story.

If your current weight puts you above the BMI healthy range, the formula average gives you a reasonable first target. Moving toward the formula average will typically bring your BMI into the healthy range, reduce cardiovascular risk markers, and improve metabolic health. If you are already within the healthy BMI range but above the formula average, there is no clinical urgency to lose more weight — you are already in a health-favorable zone.

If you are significantly below the formula average (BMI below 18.5), the priority shifts to gaining weight, specifically lean mass through resistance training and adequate protein intake. IBW formulas do not tell you how to reach a target — they only describe the target. For a calorie and activity plan to reach your target weight, use the BMR & TDEE Calculator.

How to Reach Your Ideal Weight

Whether you are above or below your ideal weight, the approach follows the same core principles: determine your caloric baseline, create the appropriate energy balance, and combine it with resistance training to protect or build lean mass.

1. Calculate your TDEE. Your Total Daily Energy Expenditure is your maintenance calorie level. Use the BMR & TDEE Calculator to find your baseline using the Mifflin-St Jeor equation and your activity level.
2. Create the right energy balance. To lose fat: eat 300–500 kcal/day below TDEE for sustainable fat loss at 0.3–0.5 kg/week. To gain lean mass: eat 250–350 kcal/day above TDEE for a lean bulk. Avoid extremes in either direction — large deficits accelerate muscle loss; large surpluses increase fat accumulation.
3. Prioritize protein. Target 0.7–1g of protein per pound of body weight (1.6–2.2g/kg). High protein intake is the most evidence-supported dietary strategy for preserving lean mass during fat loss and building muscle during a surplus.
4. Train with resistance. Resistance training 2–4× per week sends the hormonal signal to maintain or build muscle regardless of the direction of the energy balance. Without resistance training, a significant portion of weight lost comes from muscle, not fat.
5. Track body composition, not just weight. Scale weight alone is a poor indicator of progress when lean mass is changing. Take monthly waist and hip circumference measurements, or use the Body Fat Calculator with the Navy method to track fat-to-lean ratio over time.

Frequently Asked Questions

To check your BMI against the healthy range, use the BMI Calculator. To measure your current body composition, use the Body Fat Calculator with the Navy circumference method. To calculate daily calorie needs for reaching your target weight, use the BMR & TDEE Calculator. Browse all free wellness tools at Nutilz.