Ideal Weight Calculator

Find your ideal body weight using four scientific formulas, Devine, Robinson, Miller, and Hamwi. See your ideal range averaged across all formulas, a BMI-based comparison, and how your current weight compares.

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What Is "Ideal Body Weight" and Where Does It Come From?

The concept of ideal body weight (IBW) originated in the pharmaceutical industry in the mid-20th century. Clinicians needed a quick way to calculate drug dosages for patients without complex body composition data. Several formulas were developed, each using height above five feet as the primary input.

These formulas were never intended to define a single "perfect" weight for every individual. They are reference points, starting estimates that work reasonably well at a population level but have real limitations for individuals, particularly those with high or low muscle mass.

The Four Formulas Compared

This calculator uses all four major ideal weight formulas:

Devine (1974): The original and most widely cited. Men: 50 kg + 2.3 kg per inch over 5 ft. Women: 45.5 kg + 2.3 kg per inch over 5 ft.
Robinson (1983): A revision of Devine with slightly different increments. Men: 52 kg + 1.9 kg/inch. Women: 49 kg + 1.7 kg/inch.
Miller (1983): Produces higher estimates for taller individuals. Men: 56.2 kg + 1.41 kg/inch. Women: 53.1 kg + 1.36 kg/inch.
Hamwi (1964): The earliest, commonly used in nursing. Men: 48 kg + 2.7 kg/inch. Women: 45.5 kg + 2.2 kg/inch.

The spread between these formulas for a typical person is 3–8 kg. Averaging them and showing a ±10% range gives a realistic target zone rather than a falsely precise single number.

BMI vs Formula-Based Ideal Weight

The BMI-based range (weight that produces a BMI of 18.5–25) is the most commonly used clinical reference for "healthy weight." It has the advantage of being a continuous scale rather than a discrete formula, and it scales naturally with both height and the associated health risk data from large epidemiological studies.

Formula-based IBW and BMI ranges usually overlap substantially but not perfectly. For shorter individuals, the IBW formulas tend to give slightly lower targets than the BMI method. For taller individuals, the formulas may give slightly higher targets. Using both gives you a broader reference zone.

Setting a Realistic Goal Weight

The ideal weight range shown in this calculator is a useful starting point, not a mandate. A more meaningful personal target considers your individual build, athletic history, age, and how you feel at various weights.

For practical goal-setting: pick a target within the formula average range, then track body fat percentage and lean mass as you progress. A person who reaches the "ideal weight" but feels weak and has lost significant muscle should consider adjusting the target upward and focusing on body composition instead.

Frequently Asked Questions

What is my ideal weight?

There is no single "perfect" number, ideal weight ranges vary by formula, frame size, muscle mass, age, and individual health context. This calculator uses four established medical formulas and shows you the range across all of them, giving a more balanced picture than any single estimate.

Which ideal weight formula is most accurate?

All four formulas (Devine, Robinson, Miller, Hamwi) were originally developed in medical contexts for dosing purposes, not fitness targets. None is definitively "best." Averaging them reduces formula-specific bias. The BMI-based range (18.5–25 kg/m²) is the most widely used clinical reference.

What is the Devine formula?

The Devine formula (1974) is one of the oldest and most widely cited: for men, ideal weight = 50 kg + 2.3 kg per inch over 5 feet. For women, 45.5 kg + 2.3 kg per inch over 5 feet. It was originally designed for pharmaceutical dosing and tends to produce slightly lower targets.

What is the difference between the four formulas?

Devine (1974) and Robinson (1983) are the most commonly used in clinical pharmacology. Miller (1983) and Hamwi (1964) are variations developed for similar dosing purposes. All use height above 5 feet as the key variable. They differ in their base weight and per-inch increments, leading to slightly different results, typically within 3–6 kg of each other.

Does ideal weight change with age?

The standard formulas do not account for age. In practice, body composition ideals shift with age, older adults naturally have less muscle mass, so aiming for the lower end of the ideal range may be less realistic or healthy than it would be for younger adults. For older adults, maintaining muscle mass is often more important than the number on the scale.

Should I use ideal weight or BMI as my target?

Both are useful reference points but neither is a complete picture. Ideal weight formulas are simple but ignore muscle mass. BMI accounts for both weight and height but ignores body composition. For practical goal-setting, use the ideal weight range as a target zone and track body fat percentage as a more precise measure of progress.

Can I be "ideal weight" but still unhealthy?

Yes, this is called "normal weight obesity" or TOFI (thin outside, fat inside). A person can weigh within their ideal range while having high visceral fat, low muscle mass, and poor metabolic health. Body composition (lean mass vs fat mass) is ultimately a better health indicator than scale weight alone.

Is the ideal weight different for athletes?

Yes. Muscular athletes often weigh significantly above their "ideal weight" by these formulas while having very low body fat. A 180 cm male bodybuilder at 95 kg may have 8% body fat, far above the Devine ideal of ~72 kg. For athletic populations, lean body mass and body fat percentage are more meaningful targets.

How it's calculated: this tool uses established, published equations. See the full calculator methodology for the formulas and assumptions behind it.

Results are estimates for general guidance, not medical advice. See our disclaimer, and speak to a qualified healthcare professional before making medical or dietary changes.