Ideal Body Weight Formula

How to Calculate Your Ideal Body Weight

The most common way people do this is the Devine formula. It gives you a baseline number based on height and gender, nothing more. You plug in your inches and your sex assigned at birth, and you get a weight in pounds. That's it.

For men: 50 kg + 2.3 kg for every inch over 5 feet. For women: 45.5 kg + 2.3 kg for every inch over 5 feet. Convert to pounds if you need to. Multiply the kilogram result by 2.2046. The formula spits out a number, but that number is a starting point, not a destination. I ran into a case with a client who was 6'2" and came out to about 178 pounds ideal. He was a weightlifter with broad shoulders and thick bone structure. The number felt wrong because it was built for an average frame, not someone carrying 20 pounds of extra muscle on top of that frame. I ended up using a modified approach that factored in wrist circumference as a rough proxy for frame size, adding or subtracting about 10 percent depending on where he landed on the small-medium-large scale. It wasn't elegant but it was closer to reality. Another edge case that always comes up is height extremes. The formula works reasonably well from about 5'0" to 6'0". Above that, the linear addition of 2.3 kilograms per inch starts to overestimate because bodies don't scale perfectly in three dimensions. A person who is 6'6" won't have the same proportional mass as someone who is 6'0". I typically cap the calculation or switch to a body surface area method when someone is that tall. The Robinson and Miller formulas exist as alternatives and they tweak the base numbers slightly, but they have the same fundamental limitation.

What the Number Actually Means

Ideal body weight isn't a medical target. It's a reference point that was originally designed for drug dosing calculations, not fitness planning. The Devine formula came out of a pharmaceutical paper in 1974. The goal was to standardize medication dosages across different body sizes. That context matters because it tells you what the formula is good for and what it isn't. If you're trying to determine a safe weight range for health purposes, body mass index has its own problems but it was built with epidemiological data behind it. The ideal body weight formula doesn't have that layer. It's a mechanical calculation, not a health assessment tool. Some people use it as a benchmark for weight loss goals. That can work as a rough guide if you're otherwise healthy and your body type is average. It falls apart fast if you have a history of eating disorders, significant muscle mass, or a body composition that deviates from the population average the formula was built on.

The Problem with Treating It as a Target

I see this constantly. Someone calculates their ideal weight, sees a number, and then treats it like something they need to hit exactly. That approach creates more problems than it solves. The number is sensitive to how tall you are, how you measure yourself, and whether you round up or down. Two people who are the same height can have vastly different healthy weight ranges based on muscle mass, bone density, fat distribution, and overall body composition. A more useful framework is to look at a range rather than a single number. The Devine result can serve as the midpoint of a 10 to 15 percent band. If the formula says 150 pounds, then somewhere between 135 and 165 pounds might be reasonable for an average-framed person. That's still a very rough estimate, but it's less prescriptive than picking one exact weight and obsessing over it.

Other Formulas That Come Up

Besides Devine, there's the Hamwi method, which uses slightly different base weights. It's often taught in nutrition programs. The Robinson formula adjusts the per-inch addition to 1.7 kg for men and 1.5 kg for women in some versions. The Miller formula is another variation with its own constants. None of them resolve the core issue that these are all one-size-fits-all calculations based on height and sex alone. Here's what most people miss when comparing them. The differences between these formulas are small relative to the actual error margin. You're not going to get a dramatically different number by switching from Devine to Robinson. The variation between formulas is usually in the 5 to 10 pound range for most heights. What actually moves the needle more is your frame size, muscle mass, and body composition, none of which any of these formulas account for.

When to Use Something Else Instead

If you're calculating medication dosages, stick with Devine or whatever your clinical protocol specifies. That's what it was built for. If you're using this for exercise programming or nutrition planning, consider body fat percentage measurements or simple progress tracking over time instead of chasing a calculated number. A tape measure and a scale tracking trends over months is more reliable than any formula for determining whether your weight is in a healthy range for you specifically. For athletes or highly active people, lean body mass formulas like the Boer method exist but they still require additional inputs and still carry assumptions that may not apply to your body. The honest answer most of the time is that the Ideal Body Weight Formula gives you a starting reference, nothing more, and the real work of figuring out what weight is appropriate for you happens through tracking actual performance, health markers, and how you feel over time.