BMI Calculator — Free Body Mass Index Calculator for Men, Women & Kids
Free BMI calculator for men, women & kids. Metric, imperial, NHS standard — gender & age aware.
How to Use BMI Calculator
Select your gender (Male, Female, or Kids) and choose your preferred unit system
Enter your age, weight, and height in the input fields
Instantly see your BMI score, health category, and personalised advice
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No upload wait time. Results in seconds
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BMI Calculator for Women — Female Body Mass Index
The BMI calculator for women uses the standard WHO formula — weight (kg) ÷ height² (m) — but a healthy result means something slightly different for females. Women naturally carry 6–11% more body fat than men at the same BMI due to hormonal differences, which is entirely healthy. A BMI of 18.5–24.9 is the healthy BMI range for women of all ages according to NHS guidelines.
For women over 50, a BMI slightly above 25 may actually be protective against osteoporosis. Pregnant women should not use standard BMI — use your pre-pregnancy weight and consult your midwife. Our female BMI calculator shows gender-aware advice with your result.
| Women's BMI | Category | Health Note |
|---|---|---|
| Below 18.5 | Underweight | Nutrient deficiency risk — see a GP |
| 18.5 – 24.9 | Healthy weight | Normal — maintain with balanced diet |
| 25.0 – 29.9 | Overweight | Slight elevated cardiovascular risk |
| ≥ 30.0 | Obese | Consider medical advice for management |
BMI Calculator for Men — Male Body Mass Index
The BMI calculator for men applies the same formula but men typically carry less body fat at the same BMI value. In the tool above, selecting the Male mode adjusts the advice text to account for muscle mass considerations — important for gym-goers and athletes who may read "Overweight" on the BMI scale despite having excellent body composition.
A healthy BMI for men is 18.5–24.9. Men with significant muscle development (e.g., bodybuilders) should complement BMI with a DEXA scan or waist circumference measurement for accurate health assessment.
BMI Calculator by Age — Kids, Adults & Seniors
BMI for kids (2–19 years) works very differently from adult BMI. Children's body fat changes as they grow, so the NHS and CDC use BMI percentile charts rather than fixed thresholds. A child's BMI is healthy if it falls between the 5th and 84th percentile for their age and gender. Our child BMI calculator (select "Kids" mode) shows percentile guidance automatically.
For adult BMI calculator use (18–65), standard NHS thresholds apply. For seniors (65+), research suggests that a BMI of 22–27 may be optimal — slightly higher than the standard range — because lower body weight in older adults is associated with frailty and bone loss.
BMI Calculator UK — NHS Standard BMI
The NHS BMI calculator uses the WHO-standard formula and classifies adults into four categories. Zendrove follows the exact same NHS BMI chart classification shown in the expandable reference table inside the calculator above.
The BMI calculator UK (via NHS.uk) is the most used health tool in Britain. If your NHS GP or health check references your BMI, it is calculated and categorised identically to the tool on this page. For UK residents with a BMI above 30, the NHS recommends speaking to a GP about a referral to a weight management programme.
BMI Calculator India — kg & cm Units
For users in India, the BMI calculator in kg and cm (Metric kg/cm mode) is the most accurate input. However, research from the WHO and Indian Council of Medical Research (ICMR) shows that South Asians — including Indians — face higher cardiovascular and metabolic risk at lower BMI values than Western populations.
The recommended thresholds for Indian adults: Overweight ≥ 23.0 BMI (vs 25.0 standard) and Obese ≥ 27.5 BMI (vs 30.0 standard). Note: If you are checking your BMI for HDFC Life or ICICI Lombard insurance purposes, they use the standard WHO chart (cutoff 25/30), not the South Asian revised thresholds.
BMI Formula — How It Works & Its Limitations
The BMI formula is: BMI = weight (kg) ÷ height² (m). To calculate manually: convert your height to metres (e.g. 170 cm → 1.70 m), square it (1.70 × 1.70 = 2.89), then divide your weight by that number (70 kg ÷ 2.89 = 24.2 BMI).
Is the BMI calculator accurate? For population-level screening, yes. For individuals, BMI has known limitations: it cannot distinguish between muscle and fat, it may brand muscular athletes as "overweight," and it can underestimate body fat in sedentary adults with low muscle mass ("normal weight obesity"). For a more complete picture, combine BMI with waist circumference (healthy: <94 cm men / <80 cm women) or a body fat percentage reading.
Frequently Asked Questions
What is a healthy BMI for women?
For adult women, a healthy BMI is between 18.5 and 24.9, per NHS guidelines. Women naturally carry more body fat than men at the same BMI, which is normal and healthy. Pregnant women should not use standard BMI — consult a midwife instead.
What is a healthy BMI for men?
For adult men, a healthy BMI is between 18.5 and 24.9. Men with high muscle mass — such as athletes or bodybuilders — may have a BMI above 25 despite having a low body fat percentage. In these cases, body composition testing is more accurate.
What is the NHS BMI calculator?
The NHS BMI calculator uses the same WHO formula (weight in kg ÷ height in metres²) and classifies adults as Underweight (<18.5), Healthy weight (18.5–24.9), Overweight (25–29.9), or Obese (≥30). Zendrove's BMI calculator uses the same NHS classification standard.
Is the BMI calculator accurate for kids?
For children aged 2–19, standard adult BMI thresholds do not apply. Instead, BMI is interpreted using age- and gender-specific percentile charts. A result above the 95th percentile is classified as obese. Zendrove's Kids mode provides percentile guidance, but always confirm with a paediatrician.
How do I calculate BMI in kg and cm?
The BMI formula is: BMI = weight (kg) ÷ height² (m). First convert height to metres (e.g., 170 cm = 1.70 m). Then divide your weight by height squared. Example: 70 kg ÷ (1.70 × 1.70) = 70 ÷ 2.89 = 24.2 BMI.
What is the South Asian BMI threshold for India?
For South Asian populations, including Indians, the WHO recommends lower BMI thresholds — overweight is classified at 23.0 (vs 25.0) and obese at 27.5 (vs 30.0). This accounts for higher cardiovascular risk at lower BMI values seen in South Asian individuals.
Is BMI calculator accurate?
BMI is a useful screening tool but has limitations. It does not distinguish between muscle and fat, may overestimate obesity in athletes, and may underestimate it in older adults with low muscle mass. For precision, complement BMI with waist circumference measurement or a body composition scan.