How to Calculate Your Ideal Weight (Using 4 Medical Formulas)

Why Ideal Weight Is a Range, Not a Single Number

Before diving into formulas, it helps to understand why no calculator can give you one definitive number. Human bodies vary enormously. Two people who are both five feet eight inches tall can have vastly different bone structures, muscle mass distributions, and body fat percentages. One might be a competitive swimmer with broad shoulders and dense leg muscles. The other might be a long-distance runner with a narrow frame and minimal upper-body mass. Both can be perfectly healthy at different weights.

The ideal weight formulas were originally developed for clinical purposes, primarily for calculating drug dosages that scale with lean body mass. They were never intended to be the final word on what any individual should weigh. Think of them as a starting point, a reference range that provides context for conversations with your healthcare provider.

Factors that shift your personal ideal weight within (or beyond) the formula range include your skeletal frame size (small, medium, or large), your muscle mass relative to the general population, your age (body composition shifts as you get older), and your ethnic background (the formulas were developed primarily using data from Western populations). Keeping these caveats in mind, let us look at the four formulas.

The Four Major Ideal Weight Formulas

The Devine Formula (1974)

Dr. B.J. Devine published this formula in 1974, and it quickly became the most widely used ideal body weight equation in medicine. It was originally created for calculating drug dosages, not for setting weight-loss goals, but it became the de facto standard in clinical settings.

For men: Ideal weight (kg) = 50 + 2.3 x (height in inches - 60)

For women: Ideal weight (kg) = 45.5 + 2.3 x (height in inches - 60)

The Devine formula is linear, meaning it adds the same amount of weight for each inch of height above five feet. This simplicity is both its strength and its weakness. It works well for people near average height but tends to underestimate ideal weight for very tall people and overestimate it for very short people. Despite these limitations, it remains the formula most pharmacists and physicians use when they need a quick ideal body weight calculation.

The Robinson Formula (1983)

Dr. J.D. Robinson updated the Devine formula in 1983 using more recent data. The Robinson formula produces slightly different results, generally giving a somewhat higher ideal weight for women and a slightly lower one for men compared to Devine.

For men: Ideal weight (kg) = 52 + 1.9 x (height in inches - 60)

For women: Ideal weight (kg) = 49 + 1.7 x (height in inches - 60)

Robinson's modification addressed some of the criticism that the Devine formula was too aggressive in its estimate for women, particularly shorter women. The lower per-inch increment (1.7 versus 2.3 for women) means the Robinson formula does not climb as steeply with increasing height, producing a more conservative range at the taller end of the spectrum.

The Miller Formula (1983)

Also published in 1983, Dr. D.R. Miller's formula takes yet another approach. It tends to produce the highest ideal weight estimates of the four formulas, which some practitioners consider more realistic for modern populations.

For men: Ideal weight (kg) = 56.2 + 1.41 x (height in inches - 60)

For women: Ideal weight (kg) = 53.1 + 1.36 x (height in inches - 60)

The Miller formula's higher baseline and lower per-inch increment mean it produces a tighter, higher range overall. For a man at five feet ten inches, the Miller formula gives an ideal weight of about 70.3 kg (155 lbs), while the Devine formula gives about 73.0 kg (161 lbs). The differences are not enormous, but they are clinically meaningful when calculating drug dosages or setting nutritional targets.

The Hamwi Formula (1964)

Dr. G.J. Hamwi actually published the earliest of these four formulas, predating even Devine. The Hamwi formula is often used by dietitians and is notable for its simplicity when working in imperial units.

For men: 106 lbs for the first 5 feet, then add 6 lbs per inch above 5 feet

For women: 100 lbs for the first 5 feet, then add 5 lbs per inch above 5 feet

The Hamwi formula is the easiest to calculate mentally. For a woman who is five feet five inches tall, the calculation is simply 100 + (5 x 5) = 125 lbs. Hamwi also includes a built-in adjustment for frame size: add 10% for a large frame or subtract 10% for a small frame. This frame adjustment is unique among the four formulas and adds a level of personalization the others lack.

Ideal Weight Ranges by Height

The table below shows the ideal weight range for each height using all four formulas. The range spans from the lowest to the highest estimate, giving you a realistic corridor rather than a single target.

Men: Ideal Weight by Height

Women: Ideal Weight by Height

Notice how the four formulas converge around average heights and diverge as you move toward the extremes. For a five-foot-six man, the spread is only about 6 pounds. For a six-foot-two man, the spread widens to 25 pounds. This divergence reinforces the point that ideal weight is a range, not a precise target.

Frame Size and Its Impact on Ideal Weight

The Hamwi formula explicitly accounts for frame size by adjusting the result up or down by 10%. But how do you determine your frame size? The most common clinical method is wrist circumference measurement.

To measure your frame size, wrap a tape measure around your wrist at the narrowest point, just below the wrist bone. Then compare your measurement to these reference ranges:

Men

• Small frame: Wrist circumference less than 6.5 inches
• Medium frame: Wrist circumference 6.5 to 7.5 inches
• Large frame: Wrist circumference greater than 7.5 inches

Women

• Small frame: Wrist circumference less than 6 inches
• Medium frame: Wrist circumference 6 to 6.5 inches
• Large frame: Wrist circumference greater than 6.5 inches

If you have a large frame, the upper end of the formula range (or even slightly above it) may be perfectly healthy for you. If you have a small frame, the lower end is a more appropriate target. This adjustment can shift your ideal weight by 10 to 20 pounds in either direction, which is a substantial difference.

Why Muscle Mass Changes Everything

All four formulas share a fundamental limitation: they assume an average body composition. They do not know whether your weight comes from muscle, fat, bone, or water. This means a heavily muscled person will almost always exceed their calculated ideal weight while being in excellent health.

Consider a man who is five feet ten inches tall and weighs 195 pounds. By every formula, he is significantly above his ideal weight range of 153 to 166 pounds. But if a body composition test reveals he carries only 12% body fat, he has about 172 pounds of lean mass and just 23 pounds of fat. He is objectively lean and fit, despite what the ideal weight formulas suggest.

This is why healthcare providers increasingly rely on body fat percentage, waist-to-hip ratio, and waist circumference alongside or instead of ideal weight calculations. These measures better capture the health-relevant distinction between muscle and fat. If you exercise regularly, especially if you do resistance training, your ideal weight from these formulas should be treated as a loose reference, not a strict goal.

Age-Related Adjustments

None of the four formulas include age as a variable, but body composition changes significantly across the lifespan. After about age 30, adults lose approximately 3 to 8 percent of their muscle mass per decade through a process called sarcopenia. Simultaneously, body fat tends to increase, even if total body weight stays constant. This means a 60-year-old at the same weight as they were at 30 likely has a higher body fat percentage and lower muscle mass.

Some research suggests that slightly higher body weight in older adults (a BMI of 25 to 27, technically classified as overweight) is associated with lower mortality risk compared to being at the lower end of the normal range. This finding, sometimes called the obesity paradox, remains debated in the medical literature. The takeaway is not that gaining weight is beneficial, but rather that the ideal weight window may shift slightly upward as you age, and maintaining muscle mass through resistance exercise becomes increasingly important.

Ideal Weight vs. BMI: Understanding the Difference

People often confuse ideal body weight with Body Mass Index, but they measure different things. Ideal weight formulas produce a target weight in pounds or kilograms. BMI produces a dimensionless ratio by dividing weight (in kilograms) by height (in meters) squared. A BMI between 18.5 and 24.9 is classified as normal weight.

The two tools sometimes agree and sometimes conflict. If you calculate your ideal weight using the Devine formula and then calculate the BMI you would have at that weight, the result typically falls between 21 and 23, which is solidly in the normal BMI range. However, because the formulas were built on different data sets with different assumptions, they can diverge, especially at the extremes of height.

For most people, using both tools together provides a better picture than either one alone. If your ideal weight range and a healthy BMI range point in the same direction, you have strong convergent evidence. If they disagree, body composition testing can serve as the tiebreaker.

Limitations and When to Consult a Healthcare Provider

Ideal weight formulas are screening tools, not diagnostic instruments. They have several well-documented limitations that are important to keep in mind:

• Population bias. All four formulas were developed using data from primarily white Western populations. They may not accurately reflect healthy body weight ranges for people of other ethnic backgrounds, particularly Asian populations (where health risks may increase at lower body weights) or Pacific Islander populations.
• No body composition data. As discussed, the formulas cannot distinguish between lean mass and fat mass. Athletes, pregnant women, and people with significant muscle development will get misleading results.
• Height extremes. The linear nature of these formulas makes them less reliable for very short (under 5 feet) and very tall (over 6 feet 2 inches) individuals.
• Age blindness. Body composition changes with age, but the formulas produce the same result for a 25-year-old and a 75-year-old of the same height.
• Not designed for children. These formulas are for adults only. Pediatric weight assessment uses growth charts and age-specific percentiles.

You should consult a healthcare provider if your weight is significantly outside the formula range and you are unsure why, if you have a medical condition that affects body composition (such as edema or lipodystrophy), if you are pregnant or breastfeeding, or if you are considering significant dietary changes to reach an ideal weight target. A provider can order body composition testing, evaluate your overall health markers, and help you set a personalized weight goal that accounts for your unique circumstances.

How to Use Ideal Weight as a Practical Goal

If you want to use ideal weight as a target for health improvement, here is a practical approach. First, calculate your ideal weight using all four formulas and note the range. Second, determine your frame size using the wrist measurement method and adjust accordingly. Third, factor in your activity level and muscle mass. If you strength-train regularly, aim for the upper end of the range or slightly above it. If you are sedentary, the middle of the range is a reasonable starting point.

Rather than fixating on a specific number, focus on a 10-pound window within the range that feels sustainable. Rapid weight changes are rarely healthy or lasting. Aim for gradual progress of one to two pounds per week if you are losing weight, and pay attention to how you feel, your energy levels, your sleep quality, and your performance in daily activities as much as the number on the scale.

Remember that the scale measures total body weight, not health. Two people at the same weight can have dramatically different health profiles depending on their body fat distribution, cardiovascular fitness, blood markers, and metabolic health. Ideal weight is one data point among many, useful as a reference but not the whole story.