Which Ideal Weight Formula Should You Use — Hamwi, Devine, Robinson, or Miller?

If you've ever used an ideal weight calculator, you might have noticed something unsettling: it gave you a number. Just one. But the moment you look under the hood, you realize there are actually four different formulas that can produce four different answers—sometimes by 10 pounds or more. So which one should you actually follow?

The answer depends on your body type, what you're using the number for, and how much the formula was originally designed with people like you in mind. Let's walk through each formula and figure out which one makes the most sense for your situation.

Why There Are Four Formulas in the First Place

All four ideal weight formulas—Hamwi (1964), Devine (1974), Robinson (1983), and Miller (1983)—were created by doctors and researchers trying to solve a very specific problem: estimating medication doses for patients. None of them were invented to give you a single "perfect" weight to chase. That happened later, after the formulas proved convenient for health calculators.

The formulas kept getting revised because each researcher believed they could do better than the last. Devine built on Hamwi. Robinson and Miller both tried to improve on Devine. The result is that we're left with four competing answers—and unlike a math problem, there's no objectively correct one.

Hamwi Formula: The Conservative Estimate

The Hamwi formula, developed by Dr. G.J. Hamwi in 1964, produces the lowest ideal weight estimates of the four. It uses:

• Men: 48 kg for 5 feet + 2.7 kg per inch above 5 feet
• Women: 45.5 kg for 5 feet + 2.2 kg per inch above 5 feet

For a 5'9" man, Hamwi gives approximately 72 kg (159 lbs). That's notably lower than the other three formulas will produce for the same person.

When to use Hamwi: If you're on the smaller-boned side, naturally lean, or have a history of carrying extra weight easily, Hamwi gives you a more achievable and realistic target. It also tends to work better for people in their 60s and beyond, where the formula's lighter estimates may align better with what research shows is actually healthy for longevity.

The downside is that if you have a large frame or significant muscle mass, Hamwi will underestimate your healthy range. You could reach the Hamwi target and still feel too thin.

Devine Formula: The Clinical Standard

The Devine formula, published by B.J. Devine in 1974, sits in the middle of the pack and is still the gold standard in medical settings, especially in hospitals and pharmacology.

• Men: 50 kg for 5 feet + 2.3 kg per inch above 5 feet
• Women: 45.5 kg for 5 feet + 2.3 kg per inch above 5 feet

The same 5'9" man gets approximately 74 kg (163 lbs)—about 4 pounds heavier than Hamwi.

When to use Devine: If you're working with healthcare providers, your medical team is probably already using Devine for drug dosing and clinical calculations. It's the formula they know. For that reason alone, it makes sense to use it when you're talking to doctors about your weight in a clinical context. It's also a solid middle-ground choice if you're unsure about your frame size—it won't overshoot or undershoot too badly for most people of average build.

Devine is reliable, tested, and widely recognized. There's comfort in knowing that it's what's being used to calculate your medication doses.

Robinson Formula: The Population Fit

Robinson and colleagues revised Devine in 1983 to better reflect actual healthy weights in the Western population at that time. The result is somewhat higher estimates, especially for women.

• Men: 52 kg for 5 feet + 1.9 kg per inch above 5 feet
• Women: 49 kg for 5 feet + 1.7 kg per inch above 5 feet

The same 5'9" man gets approximately 75 kg (165 lbs)—just slightly higher than Devine.

When to use Robinson: This formula is the best general-purpose choice if you want something that reflects real healthy weights in modern populations. It's higher than Devine but not as extreme as Miller. If you're a woman, Robinson tends to be kinder than Devine while still being realistic. It's also a good pick if you're naturally athletic or carry more muscle than average—it gives you a little more breathing room without going overboard.

Robinson is the formula that feels "fairest" for most people in practice, which is why many modern calculators default to averaging Robinson alongside the others.

Miller Formula: The Generous Estimate

D.R. Miller published his formula independently in 1983, and it produces the highest ideal weight estimates. It was designed with the idea that people with larger bone frames or more muscle mass needed a higher ceiling.

• Men: 56.2 kg for 5 feet + 1.41 kg per inch above 5 feet
• Women: 53.1 kg for 5 feet + 1.36 kg per inch above 5 feet

That same 5'9" man gets approximately 77 kg (170 lbs)—about 8 pounds heavier than Hamwi.

When to use Miller: If you have a large frame, carry significant muscle mass, or are taller (where the height adjustments compound), Miller is your formula. It's also more appropriate if you're a strength athlete, weightlifter, or naturally broad-shouldered. If your current weight is above the Hamwi or Devine estimates but you feel strong and healthy, Miller might be the reality check that lets you stop worrying.

The risk with Miller is that it can feel like permission to carry extra body fat under the guise of muscle. Use it honestly—if you can't see your abs and don't feel athletic, Miller might be giving you too much leeway.

Head-to-Head Comparison: Which Gives You What

Here's how the four formulas stack up for a few real-world heights:

5'6" Woman:

• Hamwi: 58 kg (128 lbs)
• Devine: 60 kg (132 lbs)
• Robinson: 62 kg (137 lbs)
• Miller: 65 kg (143 lbs)

5'10" Man:

• Hamwi: 74 kg (163 lbs)
• Devine: 76 kg (168 lbs)
• Robinson: 77 kg (170 lbs)
• Miller: 80 kg (176 lbs)

Notice the spread: for a 5'10" man, it's 13 pounds from Hamwi to Miller. That's not trivial. A 160-pound woman at 5'6" according to Hamwi is "overweight" by the formula, but well within the healthy range according to Miller.

How to Actually Use These Numbers

The best approach is not to pick one formula and live by it, but to use the ideal weight calculator to see all four results and find the range where they overlap. That overlap zone is your realistic healthy range.

If all four formulas put you between, say, 155 and 170 pounds, and you're currently 160 pounds, you're almost certainly in a healthy place. The exact number matters far less than whether you're in the consensus band.

Beyond that, pay attention to how you feel. If you're at the Hamwi target and feel weak or cold all the time, you've probably gone too low. If you're at the Miller target and your doctor is warning you about blood pressure or cholesterol, something else is going on. The formulas are a starting point, not destiny.

The Real Test: Compare Against Other Metrics

The strongest signal is not any single formula, but seeing agreement across multiple measures. Check whether your weight aligns with:

• A healthy BMI (18.5 to 24.9 for most people)
• A waist circumference under 40 inches for men, 35 for women
• A body fat percentage in the healthy range for your age and sex
• Blood work (cholesterol, glucose, blood pressure) in normal ranges
• How your clothes fit and how you feel when you move

If the ideal weight formulas align with those metrics, great—use that as your north star. If they don't, trust the other signals over the formula.

Which Formula to Choose Right Now

• Small frame or history of easy weight gain: Use Hamwi. It's realistic for you.
• Talking to a doctor or clinical setting: Use Devine. That's what they're using anyway.
• Average build, want a solid middle ground: Use Robinson. It reflects real populations.
• Athletic, large frame, or significant muscle mass: Use Miller. You need the extra room.
• Unsure about yourself: Use all four and find where they overlap. That's your sweet spot.

The ideal weight calculator will show you all four results at once. That's the whole point—see them side by side, understand where you fit, and use the consensus band instead of chasing one magic number. That's how the formulas were supposed to work all along.