Ideal Weight Calculator: Comparing the Devine, Robinson & Hamwi Formulas

Ideal Weight Calculator: Comparing the Devine, Robinson & Hamwi Formulas

"What should I weigh?" doesn't have one universally agreed-upon answer — several formulas have been developed over the decades, each producing a slightly different estimate. Rather than picking one arbitrarily, comparing all three side by side gives a more realistic sense of a healthy weight range for your height.

Why Multiple Formulas Exist

These formulas weren't all created for the same purpose. The **Devine formula** (1974) was originally developed for calculating medication dosages in clinical settings, where an estimate of lean body weight mattered for accurate dosing. The **Robinson formula** (1983) and **Hamwi formula** (1964) were later refinements aimed at general population weight estimates. None of them account for individual variation in frame size or muscle mass, which is exactly why using all three together is more informative than trusting a single number.

The Three Formulas

All three use a base weight for 5 feet of height, then add a fixed amount per inch over 5 feet, with different constants for men and women:

Worked Example

For a man who is 5'9" (9 inches over 5 feet):

• •**Devine:** 50 + (2.3 × 9) = 50 + 20.7 = **70.7 kg**
• •**Robinson:** 52 + (1.9 × 9) = 52 + 17.1 = **69.1 kg**
• •**Hamwi:** 48 + (2.7 × 9) = 48 + 24.3 = **72.3 kg**

The three estimates cluster between roughly 69-72 kg — a realistic range rather than a single rigid target.

Limitations to Keep in Mind

• •**No muscle mass adjustment:** A muscular athlete will naturally weigh more than these formulas suggest while still being lean and healthy.
• •**No frame size adjustment:** Someone with a larger bone structure will reasonably weigh more at the same height than someone with a smaller frame.
• •**Population averages:** These formulas were derived from population data decades ago and don't capture individual variation.

Use the result as a general reference range, not a strict target to hit exactly — how you feel, your body composition, and overall health markers matter more than fitting a formula precisely.

How to Calculate Your Ideal Weight Online

Using the ToolzGo Ideal Weight Calculator takes seconds:

• •Go to toolzgo.com/tools/health-tools/ideal-weight-calculator
• •Select your sex and enter your height (metric or imperial)
• •See your ideal weight estimate from all three formulas side by side

Frequently Asked Questions

Q: Which ideal weight formula is most accurate?

A: No single formula is definitively "most accurate" — they were developed decades apart for different purposes. Most people fall within the range these formulas produce collectively, which is why comparing all three is more useful than relying on just one.

Q: Does this account for muscle mass?

A: No — like BMI, these formulas are based purely on height and sex, not body composition. Someone with high muscle mass may naturally weigh more than these formulas suggest while still being lean and healthy.

Q: Should I use this as a strict target?

A: Treat it as a general reference range rather than a strict target. Individual factors like frame size, muscle mass, and overall health matter more than hitting an exact number.

For a more complete picture of your body composition, check your body fat percentage with the ToolzGo Body Fat Calculator, or see your BMI category with the BMI Calculator.

Estimate your ideal weight range instantly.