Ideal Weight Calculator

About the Ideal Weight Calculator

People have been trying to define an ideal weight for well over a century, and the formulas they produced are surprisingly simple. They begin with a baseline weight for someone five feet tall and add a fixed number of kilograms for every inch above that, with slightly different numbers for men and women. This calculator uses two of the best known: the Devine formula from 1974, which was developed to help estimate medication doses, and the Robinson formula from 1983. It averages the two to give a single target, then places that number beside a second reference point, the weight range that corresponds to a BMI between 18.5 and 24.9.

Showing both is deliberate. The formula average is a point estimate based only on height and sex, and it assumes an average build. The BMI range is wider and tells you what weights are considered healthy at your height in population studies. In practice, many people find that the point estimate sits comfortably inside the range, and the range is the better guide for deciding whether a particular weight is reasonable. Having the two together shows how much room there is around the single number.

None of this accounts for the things that really shape a healthy weight for an individual: muscle mass, frame size, age, fitness, medical history, and how you feel at a given weight. An athlete or a person with a large frame can be healthy well above the range, and someone with a small frame may be healthy near the bottom of it. Use the output as a way to frame a conversation with your doctor or dietitian, not as a verdict or a number you must hit.

When to Use It

How to Use It, Step by Step

1. Choose your Sex with the dropdown. The Devine and Robinson formulas use different baselines for men and women, so the estimate changes with this selection.
2. Pick U.S. or Metric with the unit toggle. In U.S. mode, you enter height in two boxes, feet and inches. In Metric mode, you enter a single number in centimeters.
3. Enter your Height in feet and inches, such as 5 and 3, or in centimeters, such as 160. Measure without shoes against a wall if you have not done so recently, since a few inches of error shifts the result noticeably.
4. Select Calculate Ideal Weight. The tool converts your height to total inches and determines how many inches are over five feet, which is what both formulas use.
5. Read the Estimated ideal weight. In U.S. mode it is shown in pounds with the kilogram value in parentheses, and in Metric mode it is shown in kilograms with pounds in parentheses.
6. Read the Healthy BMI weight range beneath it. This is the span from a BMI of 18.5 to 24.9 at your height, shown in the same unit as the first line.
7. Compare your current weight with both. If you fall inside the range, the estimate is simply a reference point. If you are outside it, consider what you want to discuss with a healthcare provider.
8. Try nearby heights if you are unsure of your own measurement, for example an inch more or less, to see how sensitive the range is. This also helps if you are comparing yourself with family members.

Understanding Your Results

The estimated ideal weight is the average of the Devine and Robinson results. Devine uses a base of 50 kg for men and 45.5 kg for women and adds 2.3 kg per inch over five feet. Robinson uses 52 kg and 49 kg as bases, adding 1.9 kg per inch for men and 1.7 kg for women. Because the two methods differ in their slopes, they disagree more as height increases, and averaging them smooths out the gap. The result is shown in both pounds and kilograms.

The healthy BMI weight range is calculated by taking your height in meters, squaring it, and multiplying by 18.5 and 24.9. It is typically about 35 to 50 pounds wide across common adult heights, which is a reminder that healthy weight is a span, not a point. Where the formula estimate lands inside that span depends on sex and height: for the 5 ft 3 in woman in the examples below it sits in the lower half, while for the 188 cm man it sits in the upper half.

To sanity-check the output, confirm that the formula estimate lies inside or very near the BMI range. A large mismatch suggests a height entry mistake. Then consider where you are relative to both. Being a little above or below the point estimate is common and usually not a concern. Bigger gaps are worth discussing with a clinician who can consider your waist measurement, blood tests, fitness level, and medical history.

More Worked Examples

Tips for Better Results

• Pay more attention to the BMI range than to the single estimate. The range reflects a wider set of healthy builds, whereas the point estimate assumes an average frame that may not fit you.
• Measure your height in bare feet against a wall rather than using a number from a driver's license. People often overstate their height by an inch, which raises the estimate by several pounds.
• Use the estimate to set a direction, not a deadline. Moving gradually toward the range over months, with changes you can keep up, is more realistic than aiming for a specific number by a specific date.
• Consider your waist measurement alongside weight. A waist that is more than half your height is a commonly used signal of excess abdominal fat, even when weight appears reasonable.
• If you train with weights or have a large frame, expect to sit above the point estimate and perhaps above the BMI range while remaining healthy. Body fat percentage can help clarify the picture.
• Recheck the estimate after any major change in life, such as pregnancy, recovery from illness, or a shift in activity, and discuss it with a professional before starting an aggressive plan.

Common Mistakes to Avoid

• Treating the estimate as a required target. It is a statistical reference from formulas created decades ago, and healthy weights vary widely among people of the same height.
• Ignoring the BMI range because the point estimate looks lower than expected. Staying within the range is usually fine, and chasing the single number can lead to unnecessary dieting.
• Entering height in the wrong unit. Check the unit toggle before typing, because 170 in the feet field or 5 in the centimeter field will produce a meaningless answer.
• Applying the result to children or teenagers. The formulas are intended for adults, and weight in growing people is judged with pediatric growth charts and percentiles.
• Assuming a result below the range means you should gain weight. Some people are naturally lean and healthy, and a clinician should assess the cause and the risks before any advice is given.

Assumptions and Limits

• Both formulas use only height and sex. They ignore age, frame size, muscle, bone density, ethnicity, and body composition, so they cannot say what is best for a specific person.
• The formulas count inches above five feet, and the tool floors that at zero. People who are five feet or shorter therefore receive the same formula estimate, although the BMI range still adjusts to their height.
• The healthy range uses BMI cutoffs of 18.5 and 24.9 for all adults. These are population screening values, and some health organizations recommend different thresholds for certain ethnic groups.
• The results are informational and not a diagnosis or treatment plan. Talk with a doctor or registered dietitian before making major changes to your diet or exercise, especially if you have a medical condition.

Key Terms

Devine formula

A 1974 equation that estimates ideal body weight from height and sex, originally created to help calculate drug dosages.

Robinson formula

A 1983 revision of the Devine approach that uses slightly different baselines and smaller increments per inch, which gives lower estimates than Devine for most taller adults.

Ideal body weight (IBW)

A formula-based estimate of a reference weight for a given height and sex, used in medicine for dosing and in general guidance as a rough target.

Healthy BMI range

The span of weights at a given height that produce a body mass index from 18.5 to just under 25, the band associated with the lowest average risk.

Frame size

The overall bone structure of your body, often judged by wrist circumference or shoulder width. People with larger frames may healthily weigh more at the same height.

Body composition

The split of your weight into fat, muscle, bone, and water. It explains why equal weights can mean different things for different people.