Why this ratio exists
BMI treats all kilograms the same. Waist-to-height asks whether mass sits around the trunk. Public-health writers often use 0.5 as a conversation threshold — “keep your waist to less than half your height” — and 0.6 as a higher-risk band. Those cut-offs are rules of thumb from research groups such as Ashwell’s, not a WHO law printed on this page as a diagnosis.
Measure after a normal breath, tape level, midway between the lowest rib and the top of the hip bone. Do not suck in. Do not measure over a thick belt. Height should be current, the same height you use on the BMI calculator.
Worked example
Height 170 cm, waist 84 cm: ratio 0.49. Height 170 cm, waist 102 cm: ratio 0.60. Same height, different story. Pair both with walking minutes from the daily metrics note.
What a high ratio is not asking you to do
It is not asking for a wrap, a tea, or a 1,200-calorie printout. See shortcuts that do not last and crash diets. Change, if a clinician agrees, still looks like plates and walking.
Frequently asked
Does the waist-to-height 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.