Ideal Weight Calculator

What ideal weight can and cannot tell you

There is no single ideal body weight. Height sets a range within which most people have the lowest health risk at a population level, and your own healthy weight inside that range depends on muscle mass, frame size, age, illness history and what you can sustain without effort. The useful output is therefore a band, plus a set of historical formulas that show how much the estimates disagree.

The formulas here date from the 1970s and 1980s and were built for insurance tables and drug dosing, not for aesthetics. They still appear on medical calculators because drug dosing and ventilation settings sometimes still reference them, which is why they are worth showing - and worth not treating as a target.

How the formulas differ

Each formula adds a fixed number of kilograms or pounds per inch above five feet. Devine adds 2.3 kg per inch for men and the same for women from a lower base; Robinson adds 1.9 kg for men and 1.7 for women; Miller adds 1.41 and 1.36; Hamwi adds 2.7 and 2.2. Base weights differ too, from 48 to 56.2 kg for men and 45.5 to 53.1 for women.

The consequence is visible in the output: for the same height, the four formulas can spread across 8 to 12 kg. That spread is not an error in the arithmetic; it is a faithful picture of how little agreement exists about a single ideal number.

Reading your result

The first row is the healthy BMI range converted into kilograms and pounds for your height. This is the most defensible output on the page, because it comes from a population-level threshold rather than from any individual formula. The remaining rows are the four historical formulas, listed from highest to lowest, so you can see the spread for yourself.

A practical reading: if your weight sits inside the healthy range and your waist is under half your height, there is usually nothing to chase. If it sits above the range, the amount to lose is the difference between your weight and the top of the range, and a loss of 5% to 10% of body weight already improves blood pressure, blood sugar and cholesterol markers even if the range is not reached.

Why the healthy range is wide

The 18.5 to 25 BMI band spans about 20 kg for someone 178 cm tall. That width is deliberate: risk rises gradually outside it rather than at a cliff edge, and people at the same BMI can have very different amounts of muscle and visceral fat. Two people at BMI 24, one a trained athlete and one sedentary, are not in the same metabolic situation.

Waist measurement fills that gap. A waist under half your height is associated with lower cardiometabolic risk at any BMI, and a large waist at a normal BMI is a warning sign worth taking seriously. If you track one number beyond weight, make it the waist.

Frame size, muscle and age

A heavy skeleton and a broad frame shift the healthy range upwards by a few kilograms; a small frame shifts it down. Muscle mass moves it further, which is why trained people often sit above the BMI range while carrying little fat. Age moves it in the other direction: after about 65, a slightly higher BMI is associated with better outcomes than the bottom of the range, largely because low weight often reflects lost muscle.

None of these adjustments are precise enough to compute. They are reasons to read the range as a guide with a tolerance of a few kilograms in either direction rather than a pass or fail line.

What to do with the number

If you want a target, use the top of the healthy range as an upper bound and the bottom as a floor you do not need to reach. Then set the plan from your maintenance calories rather than from the target weight: a deficit of 15% to 20% with adequate protein will move you toward the range without the crash dieting that a fixed number tends to encourage.

• Use the healthy range as a band, not a goal weight.
• Track waist alongside weight; it changes faster and matters more.
• Set intake from maintenance calories, not from the target weight.
• Recheck after every 5 to 7 kg of change.

Frequently asked questions