BMI Calculator
Calculate your Body Mass Index and weight category — underweight, healthy, overweight, or obese — in metric or imperial units.
Last reviewed
Body Mass Index (BMI) screens whether your weight falls in a healthy range for your height. It's calculated as BMI = weight(kg) / height(m)², with under 18.5 classified as underweight, 18.5–24.9 as healthy, 25–29.9 as overweight, and 30+ as obese.
Current BMI
22.9
Target Weight Range
125lbs - 168lbs
Height Context
5'9"
Metrics
Strategy Note
BMI is a screening tool, not a diagnostic. A high BMI should be paired with a waist-to-hip ratio measurement for a full metabolic profile.
Start Macro AuditMetabolic Status
WHO Classification Gauge
Healthy
You are in the optimal range.
The Mathematics of Body Mass Index
The BMI formula was developed in the 19th century by Adolphe Quetelet as a way to describe how weight scales with height across a population. It's still the global standard for a quick health screen because it's cheap to measure and correlates reasonably well with body fat at a population level. As the limitation below explains, though, it can't see body composition directly.
How to measure the inputs. Weigh yourself in the morning, before eating and with minimal clothing, for the most consistent reading. Measure height without shoes, standing straight against a wall with your heels, back, and head touching it.
Worked example. Someone 175 cm tall (5'9") weighing 70 kg (155 lbs) has a BMI of 70 ÷ 1.75² ≈ 22.9 (inside the 18.5–24.9 healthy range), which is exactly what this calculator's default values show above.
For the official classification ranges and guidance on using BMI as a screening tool, see the CDC's Adult BMI Calculator and guidance.
The Quetelet Formula
Limitations. BMI doesn't distinguish muscle from fat, so very muscular people can be classified as overweight despite low body fat, and it doesn't account for age, sex, or where fat is distributed on the body. It's a screening estimate, not a diagnosis. Talk to a clinician about what your BMI means for you.
Clinical Inquiries
?Is BMI accurate for athletes?
Not always. BMI doesn't distinguish between muscle and fat. Athletes with high muscle mass may be classified as overweight despite low body fat.
?How can I lower my BMI?
Focus on a consistent caloric deficit and strength training to preserve muscle while losing fat.
About this calculator. Results are estimates for education and planning, based on the inputs you enter and the published formula described above. Everything runs in your browser; nothing you type is sent to us or stored. It is not financial, tax, legal or medical advice. Read the disclaimer and our methodology.
Spotted an error or an out-of-date figure? Tell us and we will correct it and note the change in the update log.