How to Calculate Your Ideal Body Weight

Why "Ideal" Weight Is Complicated

Walk into any doctor's office, and they'll probably tell you what you "should" weigh. But the truth is, there's no single number that represents your ideal weight. The concept itself is somewhat misleading, because the human body is too variable for a one-size-fits-all answer.

Your so-called ideal weight depends on your height, your gender, your age, your bone structure, your muscle mass, your genetics, and your personal health goals. A 6-foot-tall powerlifter and a 6-foot-tall distance runner might be the same height, but their ideal weights are wildly different because their bodies are built for different things.

That said, having some reference points is useful. Multiple clinical formulas exist that can give you a reasonable range to aim for, and understanding how they work (and where they fall short) helps you use them appropriately.

The Four Main Formulas

There are four widely cited formulas for ideal body weight, each developed by different researchers using different methods. Our Ideal Weight Calculator computes all four so you can see the range:

Devine Formula (1974). This is probably the most commonly used formula. For men: 50 kg + 2.3 kg for each inch over 5 feet. For women: 45.5 kg + 2.3 kg for each inch over 5 feet. It's simple and widely cited, though some critics argue it sets the bar a bit low.

Robinson Formula (1983). Similar to Devine but with slightly different adjustments. For men: 52 kg + 1.9 kg per inch over 5 feet. For women: 49 kg + 1.7 kg per inch over 5 feet. This tends to give slightly higher results than Devine.

Miller Formula (1983). Another variation that accounts for the observation that Devine's formula underestimates ideal weight for taller people. For men: 56.2 kg + 1.41 kg per inch over 5 feet. For women: 53.1 kg + 1.36 kg per inch over 5 feet.

Hamwi Formula (1964). Originally developed for medicinal dosage calculations. For men: 48 kg + 2.7 kg per inch over 5 feet. For women: 45.5 kg + 2.2 kg per inch over 5 feet. This one tends to produce the widest range of results.

Why Do These Formulas Give Different Answers?

It's normal to look at the results from all four formulas and see a spread of 5-10 kg (11-22 pounds) or more. That's not a flaw — it's a reflection of the fact that "ideal weight" is a range, not a point.

These formulas were all developed using different study populations at different times. Devine's original work was based on a relatively small sample. Robinson and Miller updated it with larger datasets. Hamwi had a different purpose entirely (drug dosing). Each formula captures something true about weight and height relationships, but none of them captures the whole picture.

The best approach is to look at the range — if all four formulas give you numbers between 65 and 75 kg, that's a reasonable target range. If they're all clustered around 70 kg with only small variations, that's even more confidence in the number.

The BMI Connection

Ideal weight formulas and BMI are related but measure slightly different things. BMI tells you whether your current weight is within a healthy range for your height. Ideal weight formulas try to tell you what weight within that range you should aim for.

One useful way to think about it: the "normal" BMI range (18.5-24.9) translates to a weight range for your specific height. The ideal weight formulas generally land somewhere in the middle-to-upper end of that normal range. Use our BMI Calculator to see where you currently fall.

What These Formulas Don't Account For

All four formulas share the same limitation: they don't account for body composition. As we discussed in the BMI article, muscle weighs more than fat by volume. An athlete might weigh more than their "ideal" weight and be perfectly healthy because the extra weight is lean mass, not fat.

This is why measuring body fat percentage alongside your weight gives you a much more complete picture. The Body Fat Calculator can give you an estimate using just a tape measure. Generally, healthy body fat ranges are 10-22% for men and 20-32% for women, depending on age.

Age also matters. As people get older, having a slightly higher weight (within reason) is actually associated with better health outcomes than being at the very bottom of the normal range. The ideal weight for a 25-year-old might not be the ideal weight for a 70-year-old.

A More Practical Approach

Instead of obsessing over a specific number from a formula, consider this more holistic approach:

Find your range. Use the formulas to get a ballpark figure. If they all say your ideal weight is somewhere around 70-76 kg, that's your target range.

Consider how you feel. Can you do the physical activities you want to do? Do you have energy throughout the day? Are your blood markers (cholesterol, blood sugar, blood pressure) in healthy ranges? These matter more than any number on a scale.

Focus on trends, not snapshots. Your weight fluctuates by 1-3 pounds daily based on water retention, food in your digestive system, and other factors. What matters is the trend over weeks and months, not what the scale says on any given morning.

Make sustainable changes. If you're above your target range, aim for gradual changes — about 0.5-1 pound per week. Crash diets might get you to a number faster, but they rarely stick. Slow and steady wins the race in weight management, just like in most other areas of life.