Free online BMI Calculator (Body Mass Index) for quick, accurate bmi(body mass index) results. No downloads, no account, just instant answers.
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Is this BMI calculator free to use?
Yes — this is a free BMI calculator online with no sign-up required. Enter your height and weight and calculate BMI instantly, as many times as you like.
How accurate is this BMI calculator?
This is an accurate BMI calculator based on the standard Body Mass Index formula (weight ÷ height²), the same method used by health organizations worldwide. It also shows BMI Prime and Ponderal Index for extra context.
Does this BMI calculator work with age?
Yes, this BMI calculator with age support is built for adults. BMI is interpreted differently for children and teens, so young people should check with a pediatrician instead.
How do I calculate BMI by height and weight?
Enter your height and weight above and press Calculate. This BMI calculator by height and weight instantly returns your Body Mass Index, category (e.g. Normal, Overweight), and healthy BMI range.
Can I use this BMI calculator in kg and cm, or lb and inches?
Yes — switch between Metric Units (kg and cm) and US Units (lb and inches) at any time as a BMI checker online; results recalculate instantly either way.
What counts as a healthy BMI?
For most adults, a healthy BMI generally falls between 18.5 and 25 kg/m². Use this healthy BMI calculator to see exactly where your result falls against that range.
BMI-for-age percentile (CDC growth charts), not a fixed number
Underweight <5th percentile · Healthy 5th–84th · Overweight 85th–94th · Obese ≥95th percentile
A growing child’s healthy weight shifts constantly with age and sex, so pediatric BMI is plotted on a growth chart rather than compared to the flat adult thresholds. A pediatrician is the right person to interpret it.
Standard fixed BMI categories
Underweight <18.5 · Normal 18.5–24.9 · Overweight 25–29.9 · Obese ≥30
This is the age range the standard WHO/CDC adult categories were built around, so the fixed cutoffs are most directly applicable here.
Standard fixed BMI categories
Underweight <18.5 · Normal 18.5–24.9 · Overweight 25–29.9 · Obese ≥30
The same adult categories still apply, though natural muscle loss (sarcopenia) can begin in this range — two people with an identical BMI can have very different body composition, so pairing BMI with a body-fat or waist-circumference check adds useful context.
Standard formula, wider healthy band commonly recommended
Research-supported healthy band roughly 23–30, vs. 18.5–25 for younger adults
Several geriatric studies associate a slightly higher BMI with lower mortality risk in this age group (sometimes called the "obesity paradox") — a bit of extra reserve can help buffer illness, while a low BMI is more often linked to frailty and muscle loss. Guidance varies by individual; a doctor should weigh in before treating a result as a health concern.
BMI is calculated with the standard Body Mass Index formula — weight in kilograms divided by height in meters squared (kg/m²) — the same method used by the WHO and CDC.
Your result is then placed into the standard adult categories: Underweight (below 18.5), Normal (18.5–24.9), Overweight (25–29.9), or Obese (30 and above).
Free online BMI Calculator (Body Mass Index) for quick, accurate bmi(body mass index) results. No downloads, no account, just instant answers.
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