Ideal Weight Calculator

How Ideal Weight Is Calculated: The Four Formulas

This calculator uses four clinically validated formulas, each developed by a different researcher for different medical purposes. All four use height and sex as inputs — the primary determinants of skeletal frame and lean body mass.

• Devine Formula (1974): Male = 50 kg + 2.3 kg per inch over 5 feet. Female = 45.5 kg + 2.3 kg per inch. Originally developed to calculate drug dosages in clinical settings.
• Robinson Formula (1983): Male = 52 kg + 1.9 kg per inch over 5 feet. Female = 49 kg + 1.7 kg per inch. A revision of Devine intended to better reflect population data.
• Miller Formula (1983): Male = 56.2 kg + 1.41 kg per inch over 5 feet. Female = 53.1 kg + 1.36 kg per inch. Generally produces the highest ideal weight estimates of the four.
• Hamwi Formula (1964): Male = 106 lbs + 6 lbs per inch over 5 feet. Female = 100 lbs + 5 lbs per inch. The oldest formula, widely used by dietitians for nutritional planning.

The calculator averages all four results and shows each individually, giving you a range rather than a single potentially misleading number. It also displays your healthy BMI weight range for comparison.

Why Ideal Weight Formulas Differ

The formulas were derived from different population samples, different eras, and different clinical contexts. Their differences reflect genuine uncertainty about what "ideal" means:

The Devine formula was not developed as a fitness or nutrition tool at all — it was created so pharmacists and nurses could quickly estimate drug dosages (particularly for medications dosed by lean body mass, like certain antibiotics and anesthetics). Its goal was clinical utility, not accuracy in representing a healthy weight.

The Hamwi formula, developed a decade earlier, was the standard dietitian tool for calculating protein and caloric requirements in hospitalized patients. It's the simplest to calculate mentally, which made it practical in clinical settings before calculators were ubiquitous.

The Robinson and Miller formulas were attempts to update and improve Devine using population data from the 1970s and early 1980s. They produce somewhat higher values that better reflect the actual weight distribution of healthy individuals at the time.

None of these formulas account for body composition, ethnicity, age, or muscle mass — which is why they should be treated as reference ranges, not prescriptions.

BMI vs. Ideal Weight: Which Matters More?

Both BMI and ideal weight formulas are population-level screening tools that use height as the primary variable. They share the same fundamental limitation: they cannot distinguish muscle from fat.

The key differences:

• BMI gives you a ratio (weight ÷ height²) and compares you to clinical categories (underweight, normal, overweight, obese). It's designed to flag health risk in population screenings.
• Ideal weight formulas give you a target number in pounds or kilograms. They were designed for clinical calculations (drug dosing, nutritional requirements), not for health risk assessment.
• The healthy BMI range (18.5–24.9) generally produces a wider weight range than the ideal weight formulas, which tend toward the lower end of healthy BMI.
• For most people, the ideal weight formulas land around BMI 21–23 — the sweet spot that population research associates with lowest mortality risk.

Practically: use BMI to understand your health risk category, and use ideal weight formulas as a rough long-term target for weight loss or maintenance goals. Neither is a precise individual prescription.

Healthy Weight Ranges by Height

Using the healthy BMI range of 18.5–24.9, here are the healthy weight ranges for common heights:

• 5'0": 95 – 128 lbs
• 5'2": 104 – 140 lbs
• 5'4": 108 – 145 lbs
• 5'6": 115 – 154 lbs
• 5'8": 122 – 164 lbs
• 5'10": 129 – 174 lbs
• 6'0": 136 – 184 lbs
• 6'2": 144 – 194 lbs

These ranges are wide for a reason — there is natural variation in healthy body composition even at the same height. A 5'10" man at 160 lbs and 12% body fat is equally healthy as a 5'10" man at 155 lbs and 15% body fat.

Body Composition vs. Scale Weight

The number on the scale is the least informative measure of health. Two people can weigh exactly 160 lbs at the same height and have dramatically different health profiles:

• Person A: 160 lbs, 12% body fat → 140.8 lbs lean mass, 19.2 lbs fat. Athletic, low metabolic risk.
• Person B: 160 lbs, 32% body fat → 108.8 lbs lean mass, 51.2 lbs fat. Sedentary, elevated risk for metabolic syndrome.

Both people have the same BMI and would fall in the same "healthy" category on an ideal weight chart. But their actual health status is completely different.

More useful metrics beyond scale weight:

• Waist circumference: Risk increases above 35" for women, 40" for men
• Waist-to-height ratio: Keep waist circumference below half your height — one of the strongest predictors of cardiovascular risk
• Body fat percentage: Healthy ranges are 10–20% for men, 18–28% for women (varies by age)
• Muscle mass / Lean Body Mass: More muscle = better metabolic health, bone density, and longevity

Why Muscle Weighs More Than Fat — and Why It Matters

Muscle tissue is denser than fat tissue — approximately 1.06 g/cm³ vs. 0.9 g/cm³. This means a pound of muscle takes up about 18% less space than a pound of fat. A muscular person can appear leaner and smaller while actually weighing more than expected.

This density difference has important implications for the scale:

• When you start resistance training, you may gain 2–5 lbs in the first few weeks despite looking leaner and fitting better in clothes — this is muscle gain replacing fat volume
• Body recomposition (gaining muscle while losing fat simultaneously) often produces no net weight change, which can be discouraging if the scale is your only metric
• Athletes with 10% body fat routinely land in the "overweight" BMI category — their high muscle mass pushes their weight above the BMI formula's expectations

The practical takeaway: use ideal weight and BMI as rough reference points, but track body composition (measurements, progress photos, body fat %) for a more accurate picture of your health progress.

How to Use Your Ideal Weight Result

Your ideal weight calculation gives you a range, not a magic number. Here's how to apply it sensibly:

• If your current weight is within 5–10 lbs of the average ideal weight, focus on body composition (more muscle, less fat) rather than scale weight
• If you're more than 20 lbs above, a caloric deficit combined with resistance training is the evidence-based approach — target 0.5–1 lb/week loss to preserve muscle mass
• If you're below ideal weight, a focus on adequate protein (0.7–1g per lb of body weight) and progressive resistance training will build lean mass
• Always contextualize with how you feel, your energy levels, bloodwork (cholesterol, blood sugar, blood pressure), and fitness capacity — not just the number