Free Ideal Body Weight Calculator Online

How to use the ideal weight calculator

1. Select your unit system: metric (cm, kg) or imperial (ft/in, lbs).
2. Enter your height in the input fields.
3. Select your sex (male or female).
4. The online ideal weight calculator displays results from all four formulas instantly.
5. Optionally enter your current weight to see your percent ideal body weight (%IBW).

Ideal body weight calculation formula: how each method works

All four ideal body weight formulas share the same structure: a base weight at exactly 5 feet (60 inches) plus a fixed increment for every inch above that. They differ only in the base weight and the per-inch increment. Here are all four with the actual numbers:

• Devine (1974): Men: 50 kg + 2.3 kg per inch above 60 in. Women: 45.5 kg + 2.3 kg per inch above 60 in.
• Robinson (1983): Men: 52 kg + 1.9 kg per inch above 60 in. Women: 49 kg + 1.7 kg per inch above 60 in.
• Miller (1983): Men: 56.2 kg + 1.41 kg per inch above 60 in. Women: 53.1 kg + 1.36 kg per inch above 60 in.
• Hamwi (1964): Men: 48 kg + 2.7 kg per inch above 60 in. Women: 45.4 kg + 2.2 kg per inch above 60 in.

Worked example: a man who is 5 ft 10 in (70 inches) is 10 inches above 5 feet. Using the Devine formula: IBW = 50 + (2.3 x 10) = 73 kg. Using Robinson: IBW = 52 + (1.9 x 10) = 71 kg. The four results together define a range of roughly 68 to 76 kg for this individual. That range is your healthy weight zone, not a single fixed number.

For metric input the calculator converts centimeters to inches automatically (divide by 2.54), applies the formula, then converts the result back to kilograms or pounds depending on your selected unit. The ideal weight in kg is the native output of all four formulas since they were developed using metric units.

Ideal weight calculator for women vs men: why the numbers differ

The ideal body weight calculator for women produces results that are consistently 4 to 6 kg lower than for men at the same height. This is because all four formulas use lower base weights and smaller per-inch increments for women. The gap reflects established physiological differences: men have greater average bone density and a higher proportion of skeletal muscle mass per unit of height, both of which add to body weight without adding health risk.

For example, at 5 feet 6 inches (168 cm), the Devine formula gives 63.8 kg for men and 59.3 kg for women. At 5 feet 8 inches the gap widens slightly. The ideal body weight calculator female result is therefore lower, but both outputs are calibrated to the same clinical reference standard. Women naturally carry a higher percentage of essential body fat (10 to 13 percent vs. 2 to 5 percent for men), which contributes to total body weight even in lean individuals. Pairing your ideal weight result with a body fat percentage calculator gives a more complete picture of body composition than weight alone.

Adjusted ideal body weight: what it is and when it matters

Adjusted ideal body weight (AiBW) is a clinical calculation used when a person's actual body weight exceeds their IBW by more than 20 to 30 percent. Standard IBW under-estimates lean body mass in this situation, while actual body weight over-estimates it. The adjusted ideal body weight formula corrects for this:

AiBW = IBW + 0.4 x (Actual Body Weight - IBW)

The 0.4 correction factor reflects that adipose tissue is not metabolically inert: it contributes to the distribution volume of certain drugs. AiBW is used primarily in clinical pharmacokinetics for medications including aminoglycosides (gentamicin, tobramycin), vancomycin, and heparin. Outside of clinical drug dosing, AiBW is not a weight-loss target. It is a pharmacological tool, not a fitness goal. If you are working toward a weight goal for health or performance, your ideal body weight range from the four formulas combined with your total daily energy expenditure (TDEE) is the more relevant starting point.

Percent ideal body weight (%IBW): interpreting where you stand

Percent ideal body weight expresses your current weight as a proportion of your ideal body weight:

%IBW = (Actual Body Weight / Ideal Body Weight) x 100

A %IBW of 100% means you are exactly at your ideal weight according to the formula used. Clinical interpretation ranges: 90 to 110% is considered normal; 80 to 89% is mildly underweight; below 70% indicates significant underweight or potential malnutrition. Above 110% is overweight; above 130% is used as an obesity threshold in some clinical dosing protocols. In practice, %IBW is most useful for clinical nutrition screening rather than as a day-to-day fitness metric. For a more actionable measure of body composition, compare your ideal weight result alongside your BMI score.

Limitations of ideal body weight formulas

The ideal body weight formulas were designed for clinical drug dosing in the 1960s to 1980s, not as consumer fitness targets. Their key limitations:

• No body composition data: A 175 cm man at 85 kg with 12% body fat will far exceed his IBW range despite being extremely lean. The formulas have no way to distinguish muscle from fat.
• No frame size adjustment: Large-framed individuals with wider skeletal structure will naturally weigh more than the formulas suggest without any health risk.
• Binary sex input: The formulas only account for binary male/female physiological differences and do not accommodate non-binary individuals or those undergoing hormonal changes.
• Not validated below 5 feet: All four formulas use increments above 60 inches (5 feet). For individuals below 5 feet tall, the formulas can produce inaccurate or negative results and should not be relied upon.

For a more complete health picture, use your ideal weight result alongside your BMI, body fat percentage, and daily calorie needs to understand where you stand and what adjustments, if any, are appropriate for your goals.