How to calculate BMI
To calculate your BMI, open the ToolCrix BMI Calculator, choose metric or imperial, and enter your height and weight. BMI is your weight in kilograms divided by your height in metres squared (kg/m²). A reading of 18.5–24.9 is considered the healthy range. The calculator also estimates body-fat, BMR and your ideal weight range.
Want to calculate your BMI and understand what it means? This free BMI calculator works in metric and imperial, shows your category on a clear scale, and also estimates body-fat, BMR and ideal weight — all privately in your browser.
What BMI is and why it's useful
Body Mass Index (BMI) is a quick screen that relates your weight to your height (kg ÷ m²). It's a useful starting point for understanding whether you're in a healthy weight range for your height.
BMI is a screening tool, not a diagnosis — it doesn't distinguish muscle from fat. That's why this tool also estimates body-fat percentage and your daily calorie needs for a fuller picture.
How to use it (step by step)
- Open the BMI Calculator.
- Choose metric or imperial units.
- Enter your height and weight (and age/sex for extra metrics).
- Read your BMI and category on the colour-coded scale.
- Review the body-fat, BMR and ideal-weight estimates.
What you can use it for
- Checking if your weight is in a healthy range for your height.
- Setting a weight goal with an ideal-weight range.
- Estimating daily calorie needs (BMR/TDEE).
- Tracking progress over time.
- A quick health screen before seeing a professional.
BMI categories
- Under 18.5 — underweight
- 18.5–24.9 — normal weight
- 25–29.9 — overweight
- 30+ — obese
Tips
- BMI doesn't account for muscle — athletes may read ‘overweight’ while lean.
- Use it as a trend over time, not a single verdict.
- Pair BMI with the body-fat estimate for context.
- Always consult a professional for medical decisions.
Frequently Asked Questions
How is BMI calculated?
BMI = weight in kilograms divided by height in metres squared (kg/m²). The tool does it for you in metric or imperial.
What is a healthy BMI?
A BMI between 18.5 and 24.9 is generally considered the normal/healthy range.
Is the BMI calculator free?
Yes — free, instant and private, with no sign-up.
Is BMI accurate for everyone?
It's a screening tool and doesn't separate muscle from fat, so very muscular people may read high. Use it alongside other measures.
Does it estimate body fat and calories?
Yes — it also estimates body-fat percentage, BMR and daily calorie needs.
What is a healthy BMI for adults?
18.5 to 24.9 is generally considered the healthy range for adults. Under 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese — but BMI doesn't separate muscle from fat, so very muscular people may read high.
How is BMI different from body-fat percentage?
BMI is a quick screen based only on height and weight. Body-fat percentage is more accurate but harder to measure. The ToolCrix calculator estimates both so you get a fuller picture.
Try it now: open the free BMI Calculator or the Percentage Calculator, or browse more guides.