This free BMI calculator lets you check your Body Mass Index using either metric (kg/cm) or imperial (lb/ft+in). It works for adults and gives you a simple category: underweight, healthy weight, overweight, or obese. This style of BMI lookup is similar to what a typical NHS BMI calculator shows in practice, where BMI is used as a quick screening number for genaperal health.
Instead of asking “What’s my BMI?”, this part flips it around. This reverse BMI calculator (sometimes called a backwards BMI calculator) lets you enter a target BMI and your height, and it will estimate what body weight lines up with that BMI. People use this when they’re aiming for a certain range like “healthy weight” and want a rough idea of the target.
BMI (Body Mass Index) is a simple ratio of weight and height. It’s widely used by clinics and public health guides, including NHS-style healthy weight ranges, to flag possible underweight, overweight, or obesity in adults. It’s the same basic calculation for men and women.
But BMI is only one signal. It does not directly measure body fat, muscle, bone density, hormones, age, or overall health. For example, a very strong athlete can get labeled “overweight” even if they’re lean. And in teens, BMI is compared differently (by age and sex percentile), so a question like “what is the average weight for a 13 year old?” can’t be answered with one number for everyone — growth and puberty timing matter a lot.
BMI also breaks down for some groups, including people with limb difference or amputation. In those cases, “body weight” on the scale is lower because part of the body mass is missing, so classic BMI underestimates or overestimates health risk unless you adjust the weight first. A common approach in bmi calculator amputation / bmi calculator amputee tools is to estimate what your weight would be with all limbs attached, then run the normal BMI formula using that adjusted weight. This is because typical BMI charts were built for people without amputations.
You might also see other body shape indexes online, like “BRI calculator” (Body Roundness Index) or body fat estimators. Those tools try to factor in waist, hips, or body shape instead of just height and weight. BMI is still the most common first check because it’s fast and easy to calculate.
Bottom line: use BMI as a quick snapshot, not a final judgment. If your result worries you — especially if it’s in the obese or underweight range — talk to a health professional who can look at the bigger picture.
| Category | BMI Range |
|---|---|
| Underweight | < 18.5 |
| Healthy weight | 18.5 – 24.9 |
| Overweight | 25 – 29.9 |
| Obese | 30+ |