BMI calculator
Calculate your Body Mass Index (BMI) from height and weight, and see which weight category you fall into.
What is BMI?
Body Mass Index (BMI) is a screening measure that relates your weight to your height, giving a quick, standardized way to flag whether your weight falls in a range associated with lower or higher health risk. It's the same formula used by doctors, insurers, and public health bodies worldwide precisely because it only needs two easy-to-measure inputs — no lab equipment required.
Does BMI differ for men and women?
The formula and the four category cutoffs are identical for adult men and women — there is no separate "male" or "female" BMI scale. What does differ is body composition: at the same BMI, women typically carry a higher percentage of body fat than men, because BMI can't tell fat mass from muscle mass. That's why we ask for sex on this calculator — not to change the number, but to give you a result note that reflects how that number tends to play out for your body composition.
BMI's main limitation: it can't see muscle
Because BMI is just weight divided by height squared, it treats a kilogram of muscle the same as a kilogram of fat. That makes it a poor fit for very muscular athletes (who can read as "overweight" despite low body fat) and for older adults who have lost muscle mass (who can read as "healthy" despite a high body fat percentage). Use it as a first-pass screening tool, not a precise body-composition measurement — our Body Fat % calculator gets closer to that.
Tips for maintaining a healthy BMI
- Favor consistency over crash diets. Slow, sustained changes in weight are far more likely to stick than aggressive short-term cuts.
- Strength train, not just cardio. Preserving or building muscle improves body composition even when the number on the scale barely moves.
- Track trends, not single readings. Weight fluctuates day to day with water and food — a weekly average tells you far more than any one measurement.
- Prioritize sleep and stress. Both directly affect appetite hormones and can undermine an otherwise solid nutrition plan.
BMI categories
| Category | BMI range |
|---|---|
| Underweight | < 18.5 |
| Healthy weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese | ≥ 30.0 |
Frequently asked questions
What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight range. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is classified as obese. These ranges are the same for adult men and women.
Does the BMI formula or category ranges differ between men and women?
No. The World Health Organization and CDC use the same formula and the same four category cutoffs (18.5, 25, 30) for adult men and women. Selecting your sex on this calculator doesn’t change the number — it only tailors the context in the result, since men and women with an identical BMI tend to carry that weight differently.
What is a healthy BMI for women?
The healthy range is the same as for men — 18.5 to 24.9. In practice, women typically carry a higher body fat percentage than men at the same BMI, because BMI can’t distinguish fat mass from lean mass. That’s worth keeping in mind when interpreting the number, especially around pregnancy, menopause, or significant muscle gain.
What is a healthy BMI for men?
The healthy range is 18.5 to 24.9, same as for women. Men generally carry more muscle mass on average, so a man near the top of the "healthy" range or just into "overweight" may still have a low body fat percentage — particularly if he trains regularly.
Is BMI accurate for everyone?
BMI is a useful screening tool but does not directly measure body fat. It can overestimate body fat in muscular athletes of either sex and underestimate it in older adults who have lost muscle mass, regardless of gender.
How is BMI calculated?
BMI = weight (kg) / height (m)². When using pounds and inches, the formula is BMI = 703 × weight (lb) / height (in)². Sex is not a variable in the formula itself.
Why might BMI be misleading for athletes or very muscular people?
Because BMI only looks at total weight relative to height, it can’t tell muscle from fat. A muscular man or woman can land in the "overweight" category despite having a low, healthy body fat percentage. If that sounds like you, our Body Fat % calculator gives a more direct read on body composition.