The equations
Devine (1974) is still used in some medicine-dose calculations: men 50 kg plus 2.3 kg per inch over 5 feet; women 45.5 kg plus 2.3 kg per inch over 5 feet. Robinson (1983) uses slightly different constants. Miller (1983) starts higher and adds less per inch: men 56.2 kg plus 1.41 kg per inch over 5 feet; women 53.1 kg plus 1.36 kg per inch over 5 feet. None of the three watched your walking minutes or your waist.
Compare the output with the healthy BMI band on the BMI calculator. Those two numbers will not match exactly. That mismatch is the lesson. Read what BMI is and where it fails before you treat either figure as a shopping list.
Worked example
A woman 168 cm tall is about 66.1 inches, 6.1 inches over 60. Devine: 45.5 + 2.3 × 6.1 ≈ 59.5 kg. Robinson: 49 + 1.7 × 6.1 ≈ 59.4 kg. Miller: 53.1 + 1.36 × 6.1 ≈ 61.4 kg. The three answers already disagree. Her BMI-healthy band on this site will be a range, not a single kilogram. If she lifts and has a quiet waist, any of these “ideal” figures can sit below the weight she actually functions at.
What to do instead of chasing the number
Walk. Eat from the foods list. If energy is under discussion with a clinician, use the calorie calculator. If the issue is a joint, skip the ideal-weight page and open knees or hips.
Frequently asked
Does the ideal-weight calculator store what I type?
No. The arithmetic runs in your browser. See the privacy page.
Is this medical advice?
No. Read the medical disclaimer. Take unusual results to a clinician.
Should children use this?
No. These tools are written for adults.
How does this sit next to BMI?
Use the BMI calculator as a size snapshot, then return here for the question this page actually answers.
What should I read after the number?
Food: meal framework. Joints: knees or back. Metrics: adult indicators.
Formulas are named on the page. They are planning maths, not clinic devices.
Using the result in a normal week
Write the figure once. Do not recalculate after every meal. Recalculate when weight has changed by several kilograms, when a clinician has changed a medicine that affects weight or heart rate, or when your job has become much more or much less physical. Daily recalculation is how a useful tool becomes noise.
Food still comes from the meal framework, the foods list, and the dinner templates in the journal. Movement still comes from walking and from the mobility articles when a joint is the limit. Metrics still come from waist, blood pressure, and sleep on the adult-indicator pages.
If the result looks extreme, assume the inputs or the equation limits before you assume your body is extreme. Heights typed in the wrong unit are the usual villains. Then talk to a person who can examine you.
Keep the same units you used last time. Measure height once against a wall and write it in the notebook you already keep for waist, morning weight, and walks. Consistency beats precision theatre.
Using the result in a normal week
Write the figure once. Do not recalculate after every meal. Recalculate when weight has changed by several kilograms, when a clinician has changed a medicine that affects weight or heart rate, or when your job has become much more or much less physical. Daily recalculation is how a useful tool becomes noise.
Food still comes from the meal framework, the foods list, and the dinner templates. Movement still comes from walking and from the mobility articles when a joint is the limit. Metrics still come from waist, blood pressure, and sleep — see adult indicators and home blood pressure.
Shortcuts that promise to replace this work are collected in why crash diets fail and teas, wraps, and shortcuts. Read those if the reason you opened a calculator was a product promise rather than a planning question.
If the result looks extreme, assume the inputs or the equation limits before you assume your body is extreme. Heights under 140 cm or weights typed in the wrong unit are the usual villains. Then talk to a person who can examine you. A second calculator tab is not that person.
Keep the same units you used last time. Mixing pounds and kilograms, or inches and centimetres, is the most common way to get a theatrical result. When in doubt, measure height once against a wall and write it in the notebook you already keep for waist, morning weight, and walks. Consistency beats precision theatre.