How to Calculate Ideal Weight: 4 Formulas, Worked Examples, and the Healthy Range
If you want to learn how to calculate ideal weight, you only need two inputs: your height and your sex. Every classic formula starts from a base weight at 5 feet tall and adds a fixed amount for every inch above that. The arithmetic takes under a minute, and this guide walks through all four formulas with worked examples for a man and a woman.
The catch is that the four formulas disagree. For the same person they can differ by 4 to 5 kilograms, and none of them knows your muscle mass, frame size, or age. That is why learning how to calculate ideal weight means learning the range, not chasing one magic number.
Quick Answer: How to Calculate Ideal Weight?
Here is how to calculate ideal weight in two steps. First, count how many inches you are over 5 feet. Second, plug that number into the Devine formula: men start at 50 kg and add 2.3 kg per inch over 5 feet, women start at 45.5 kg and add 2.3 kg per inch over 5 feet.
A man who is 5 feet 10 inches tall is 10 inches over 5 feet, so his Devine ideal weight is 50 plus 23, which is 73 kg, about 161 lb. A woman who is 5 feet 4 inches tall is 4 inches over 5 feet, so her Devine ideal weight is 45.5 plus 9.2, which is 54.7 kg, about 121 lb. If you want to skip the arithmetic, our ideal weight calculator runs all four formulas at once. ClinCalc, a clinical reference used by pharmacists, explains the same Devine equation and its dosing uses in its ideal body weight guide (ClinCalc, Ideal Body Weight Calculator).
What Is Ideal Body Weight?
Ideal body weight, usually shortened to IBW, is a reference weight calculated from height and sex. It was never meant to be a beauty target. The formulas were built for clinical work: dosing drugs that spread mostly through lean tissue, setting ventilator volumes based on lung size rather than total body weight, and giving dietitians a quick reference number.
That origin matters. A dosing formula only needs to be close enough to be safe, and it assumes an average frame with average muscle. It does not know whether you lift weights, carry broad shoulders, or have a small frame. So when you learn how to calculate ideal weight, treat the answer as a reference point, the way a clinician would, not as a verdict on your body. That is why learning how to calculate ideal weight starts with what the number was built for.
How to Calculate Ideal Weight With the Devine Formula
The Devine formula is the most widely used of the four, and the one hospitals still use for drug dosing. It was published by Dr. B. J. Devine in 1974 for gentamicin dosing, and it became the clinical default.
Men: IBW = 50 kg + 2.3 kg x (height in inches minus 60).
Women: IBW = 45.5 kg + 2.3 kg x (height in inches minus 60).
The 60 stands for 5 feet, which is 60 inches. You only count the inches above that line.
Worked example: a man, 5 feet 10 inches (178 cm). In imperial units, he is 70 inches tall, so 70 minus 60 is 10 inches over 5 feet. His Devine ideal weight is 50 plus (2.3 x 10) = 50 plus 23 = 73.0 kg. In pounds, 73.0 x 2.20462 = 160.9, about 161 lb.
In metric units, convert first: 178 cm divided by 2.54 = 70.1 inches, about 70 inches. Then the same step gives 73.0 kg. Both routes land on the same number, which is a good way to check your work when you learn how to calculate ideal weight from metric height.
Worked example: a woman, 5 feet 4 inches (163 cm). In imperial units, she is 64 inches tall, so 64 minus 60 is 4 inches over 5 feet. Her Devine ideal weight is 45.5 plus (2.3 x 4) = 45.5 plus 9.2 = 54.7 kg. In pounds, 54.7 x 2.20462 = 120.6, about 121 lb.
In metric units, 163 cm divided by 2.54 = 64.2 inches, about 64 inches, and the same step gives 54.7 kg. Devine is the formula to use when a hospital, a dosing chart, or a clinical source names one formula without saying which. This is the core step in how to calculate ideal weight the clinical way.
How to Calculate Ideal Weight With the Robinson Formula
The Robinson formula is a 1983 refinement of Devine, fitted to newer Metropolitan Life Insurance Company data. It starts higher at 5 feet but adds weight more slowly per inch, so it lands close to Devine for average heights.
Men: IBW = 52 kg + 1.9 kg x (height in inches minus 60).
Women: IBW = 49 kg + 1.7 kg x (height in inches minus 60).
Same man, 5 feet 10 inches: 52 plus (1.9 x 10) = 52 plus 19 = 71.0 kg, about 157 lb. That is 2 kg below his Devine result of 73.0 kg.
Same woman, 5 feet 4 inches: 49 plus (1.7 x 4) = 49 plus 6.8 = 55.8 kg, about 123 lb. That is 1.1 kg above her Devine result of 54.7 kg.
Robinson is a good cross-check on Devine. When the two agree within a couple of kilograms, you can trust the middle of the range. When they split further apart at taller heights, the range itself is the honest answer. When you learn how to calculate ideal weight with Robinson, you are really learning how much the answer can move.
How to Calculate Ideal Weight With the Miller Formula
The Miller formula, also from 1983, starts higher still at 5 feet but has the gentlest slope of the four. It tends to give the highest numbers for shorter people and the lowest numbers for taller people.
Men: IBW = 56.2 kg + 1.41 kg x (height in inches minus 60).
Women: IBW = 53.1 kg + 1.36 kg x (height in inches minus 60).
Same man, 5 feet 10 inches: 56.2 plus (1.41 x 10) = 56.2 plus 14.1 = 70.3 kg, about 155 lb. That is the lowest of his four results.
Same woman, 5 feet 4 inches: 53.1 plus (1.36 x 4) = 53.1 plus 5.44 = 58.5 kg, about 129 lb. That is the highest of her four results.
Miller is most useful as the top of the range for shorter women and the bottom of the range for taller men. On its own it looks like an outlier. Next to the other three, it marks the edge of the plausible band. That edge matters when you learn how to calculate ideal weight for shorter or taller people, because the formulas diverge most at the extremes.
How to Calculate Ideal Weight With the Hamwi Formula
The Hamwi formula is the oldest of the four, published by Dr. G. J. Hamwi in 1964 as a quick rule for dietitians and diabetes care. It has the steepest slope, so it runs highest for tall people.
Men: IBW = 48 kg + 2.7 kg x (height in inches minus 60).
Women: IBW = 45.5 kg + 2.2 kg x (height in inches minus 60).
Same man, 5 feet 10 inches: 48 plus (2.7 x 10) = 48 plus 27 = 75.0 kg, about 165 lb. That is the highest of his four results.
Same woman, 5 feet 4 inches: 45.5 plus (2.2 x 4) = 45.5 plus 8.8 = 54.3 kg, about 120 lb. That is the lowest of her four results.
Hamwi is the easiest to do in your head, which is why dietitians kept it alive for decades. For a tall man it gives the top of the range, and for a shorter woman it gives the bottom. It is the simplest route when you learn how to calculate ideal weight by hand.
All Four Formulas Side by Side
Here is how to calculate ideal weight for the same two people with every formula, so you can see the full spread instead of one number.
| Formula | Man, 5 ft 10 in | Woman, 5 ft 4 in |
|---|---|---|
| Devine (1974) | 73.0 kg (161 lb) | 54.7 kg (121 lb) |
| Robinson (1983) | 71.0 kg (157 lb) | 55.8 kg (123 lb) |
| Miller (1983) | 70.3 kg (155 lb) | 58.5 kg (129 lb) |
| Hamwi (1964) | 75.0 kg (165 lb) | 54.3 kg (120 lb) |
| Range | 70.3 to 75.0 kg | 54.3 to 58.5 kg |
| Average | 72.3 kg (159 lb) | 55.8 kg (123 lb) |
The man spans 4.7 kg across the four formulas. The woman spans 4.2 kg. Neither spread is an error. Each formula was fitted to different data for a different purpose, so the range is the real result. Running all four is the most honest way to learn how to calculate ideal weight, because the spread is the result. If you need one number for a dosing chart, use Devine. If you are setting a personal reference, use the average and keep the whole range in mind.
Which Ideal Weight Formula Is Most Accurate, Devine, Robinson, Miller, or Hamwi?
No single formula is most accurate, because accuracy depends on the purpose. Devine is the clinical default and the one to use for dosing references, since hospitals and pharmacists use it. Robinson and Miller are refinements fitted to population data. Hamwi is the oldest quick rule. For personal use, the honest answer is the range across all four, checked against your healthy BMI range, rather than any one formula. That is why learning how to calculate ideal weight means learning the range.
What Is Your Ideal Weight by Height?
This chart gives the Devine result for common heights, plus the healthy BMI weight range for the same heights. Devine is the clinical default, and the BMI range is the wider band that modern guidance uses for general health. This chart makes it easy to see how to calculate ideal weight at a glance for common heights.
| Height | Devine men | Devine women | Healthy BMI range (18.5 to 24.9) |
|---|---|---|---|
| 5 ft 0 in | 50.0 kg (110 lb) | 45.5 kg (100 lb) | 43.0 to 57.8 kg |
| 5 ft 2 in | 54.6 kg (120 lb) | 50.1 kg (110 lb) | 45.9 to 61.8 kg |
| 5 ft 4 in | 59.2 kg (131 lb) | 54.7 kg (121 lb) | 48.9 to 65.8 kg |
| 5 ft 6 in | 63.8 kg (141 lb) | 59.3 kg (131 lb) | 52.0 to 70.0 kg |
| 5 ft 8 in | 68.4 kg (151 lb) | 63.9 kg (141 lb) | 55.2 to 74.3 kg |
| 5 ft 10 in | 73.0 kg (161 lb) | 68.5 kg (151 lb) | 58.5 to 78.7 kg |
| 6 ft 0 in | 77.6 kg (171 lb) | 73.1 kg (161 lb) | 61.9 to 83.3 kg |
| 6 ft 2 in | 82.2 kg (181 lb) | 77.7 kg (171 lb) | 65.4 to 88.0 kg |
Check one row: at 5 feet 10 inches, the healthy BMI range comes from 18.5 x (1.778 squared) = 58.5 kg at the low end and 24.9 x (1.778 squared) = 78.7 kg at the high end. Every Devine number in the chart sits inside its BMI range. That is the cross-check that tells you the formulas and the BMI range are telling a consistent story.
Ideal Weight vs the Healthy BMI Range: Why the Range Wins
The ideal weight formulas give you a point, or a narrow band of points. The healthy BMI range gives you a wide band, usually 15 to 20 kg wide at a given height. For most people, the wide band is the more useful target, for three reasons.
First, the BMI range reflects real human variety. Two people at the same height can both be healthy 15 kg apart because of bone structure, muscle, and body composition. A single formula number erases that variety. Second, the formulas were built for dosing, not for lifestyle goals, so their precision is borrowed, not earned. Third, a range is easier to live with: you can aim for the middle of the range instead of chasing one exact kilogram.
A practical way to use both: take your Devine number as a reference, then check where it sits inside your BMI range. If your Devine number is near the middle of the range, the two systems agree and you have a solid reference. If your weight sits inside the BMI range but above your Devine number, that is normal, especially if you carry muscle. That is the key lesson in how to calculate ideal weight for real life: the range beats the point. Our BMI calculator shows your exact BMI, and our guide to how to calculate BMI walks through the math.
Is Ideal Body Weight the Same as BMI?
No. Ideal body weight is a target weight from a height-and-sex formula, while BMI is a ratio of your current weight to your height squared. BMI tells you where your actual weight falls: below 18.5 is underweight, 18.5 to 24.9 is the healthy range, 25 to 29.9 is overweight, and 30 or above is obese. The two systems agree more than they disagree: every formula result in this guide sits inside its healthy BMI range. That is why learning how to calculate ideal weight and checking your BMI together gives the fullest picture. Use BMI for screening and the formula range for a reference point.
Does Frame Size Change Your Ideal Weight?
Yes, by roughly 10 percent in either direction. All four formulas assume a medium frame, which means average bone width and bone density for your height. A large-framed person with broad shoulders and heavy bones can healthily weigh about 10 percent more than the formula says. A small-framed person can healthily weigh about 10 percent less.
The quick test is the wrist wrap: wrap the thumb and middle finger of one hand around the wrist of the other. If the fingertips overlap comfortably, your frame is likely small. If they just touch, it is medium. If a gap remains, it is large.
Take the 5 feet 10 inch man with a Devine result of 73.0 kg. A small frame would put his reference near 65.7 kg, and a large frame near 80.3 kg. That 15 kg swing is bigger than the spread between all four formulas, which is why frame size deserves more attention than most ideal weight pages give it. Frame size is the biggest variable that learning how to calculate ideal weight will not show you.
What Are the Limits of Ideal Weight Formulas?
Four limits matter most when you learn how to calculate ideal weight and interpret the result.
Muscle is invisible to the formulas. A lifter with a lot of muscle can weigh well above every formula result and still be lean and healthy. The formulas only see height and sex, so they cannot tell muscle from fat.
Age is missing. The formulas do not adjust for age. Older adults naturally lose some muscle and bone density, so a weight that was right at 30 may not be the right reference at 65. Use the numbers as a starting point and weigh them against how you feel, move, and test.
Ethnicity and build are missing. The formulas were fitted to specific populations decades ago. People with different average builds can sit healthily outside the formula band, which is another reason the BMI range is a better everyday target than any single formula number.
Below 5 feet, the formulas break. The equations assume height above 5 feet. For someone shorter than 5 feet, the classic formulas just return the 5-foot base weight, which is not a real answer. Children and teenagers should never use these formulas at all, since they are still growing and need age-based growth charts.
Does Ideal Weight Change With Age?
When you learn how to calculate ideal weight, remember the formulas themselves do not include age, so the calculated number stays the same as you age. Your healthy weight can still shift, because muscle mass and bone density change over time and activity levels change with them. An older adult who has lost muscle may be healthy at a lower weight than the formula suggests, while an active older adult may sit higher. Use the formula number as a reference and judge the full picture with your doctor.
What to Do With Your Number
Once you know how to calculate ideal weight, the number is only useful if it turns into a plan.
If you are inside your healthy BMI range: your weight is already in a healthy band. Shift your attention from the scale to habits: strength, sleep, and steady activity. Chasing a lower formula number inside an already healthy range buys little and can cost a lot.
If you are above the range: a realistic first goal is 5 to 10 percent below your current weight, not a jump straight to the formula number. A 5 to 10 percent loss already improves blood pressure, blood sugar, and joint load. From there, reassess. Our guide to how many calories a day shows how to size your intake, and our guide to how to calculate BMR covers your resting burn. If the scale is stuck despite steady effort, our guide to why am i not losing weight covers the common reasons.
If you are below the range: talk to a doctor before trying to gain or lose further, especially if the gap is large or the weight loss was unintentional. A low weight with fatigue, missed periods, or frequent illness deserves a medical check, not a DIY plan.
Do not chase the lowest number. The formulas disagree by 4 to 5 kg for a reason: no single number is the truth. Picking the lowest formula result as a goal is a common path to under-eating, and it has nothing to do with health. If thoughts about weight are becoming hard to control, reach out to a doctor or an eating-disorder support service. The number on the scale is never worth your health.
Frequently Asked Questions
1. How to calculate ideal weight for my height?
To learn how to calculate ideal weight for your height, count the inches you are over 5 feet, then use the Devine formula: men start at 50 kg and add 2.3 kg per inch, women start at 45.5 kg and add 2.3 kg per inch. For example, a man who is 5 feet 10 inches tall is 10 inches over 5 feet, so his Devine ideal weight is 50 plus 23, which is 73 kg. For a fuller picture, run all four formulas and use the range, then check where it sits inside your healthy BMI range.
2. What should a woman of 5 feet 3 inches weigh?
A woman who is 5 feet 3 inches tall has a Devine ideal weight of 45.5 plus (2.3 x 3), which is 52.4 kg, about 116 lb. The other formulas give 52.1 to 57.2 kg, so the four-formula range is roughly 52 to 57 kg. Her healthy BMI range is wider: 47.4 to 63.8 kg. Any weight inside that BMI band can be healthy depending on frame and muscle, so use the Devine number as a reference, not a rule.
3. What is the average weight for a 6 feet 3 inch male?
For a man who is 6 feet 3 inches tall, the Devine formula gives 50 plus (2.3 x 15), which is 84.5 kg, about 186 lb. Note that ideal weight and average weight are different things: ideal weight is a formula reference, while average weight is what men that height actually weigh, which is higher in most modern populations. His healthy BMI range is 67.1 to 90.4 kg, so the Devine number sits comfortably inside it.
4. What is the correct weight for a 5 feet 5 inch female?
There is no single correct weight, but the Devine formula gives a woman who is 5 feet 5 inches tall 45.5 plus (2.3 x 5), which is 57.0 kg, about 126 lb. The four-formula range is 56.5 to 59.9 kg. Her healthy BMI range, which is the more useful target, is 50.4 to 67.9 kg. Frame size moves the reference by about 10 percent either way, so a large-framed woman can healthily sit above 57 kg.
5. What is the ideal weight for a 5 feet 9 inch male?
A man who is 5 feet 9 inches tall has a Devine ideal weight of 50 plus (2.3 x 9), which is 70.7 kg, about 156 lb. The other formulas give 68.9 to 72.3 kg, so the four-formula range is roughly 69 to 72 kg. His healthy BMI range is 56.8 to 76.5 kg. If he lifts weights, he can healthily sit above the formula range, because the formulas cannot see muscle.
