BMI Calculator
Check your Body Mass Index in seconds. See where you fall on the scale and what your healthy weight range looks like.
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What is BMI and why does it matter?
Body Mass Index is a 200-year-old formula invented by Belgian mathematician Adolphe Quetelet. It divides your weight by your height squared to produce a single number. Doctors, insurers, and public health researchers use it because it's fast, free, and correlates with health outcomes at the population level.
A BMI between 18.5 and 24.9 is associated with the lowest risk of cardiovascular disease, type 2 diabetes, and all-cause mortality in most large-scale studies. Outside that range, risks increase — though the relationship isn't perfectly linear.
The limits of BMI (and what to use instead)
BMI can't distinguish between muscle and fat. A bodybuilder and an obese person can have the same BMI with completely different health profiles. It also doesn't account for where fat is stored — visceral belly fat is far more dangerous than subcutaneous fat on your thighs.
Better alternatives include waist-to-height ratio (keep your waist under half your height), body fat percentage (via DEXA or calipers), and waist circumference (<40 inches for men, <35 for women). Use BMI as a quick check, not a diagnosis.
How to reach a healthy BMI
If your BMI is above 25, the math is straightforward: create a calorie deficit. A deficit of 500 cal/day leads to roughly 0.5 kg (1 lb) per week of weight loss. Use our calorie deficit calculator to plan your timeline, and our TDEE calculator to know your baseline.
The hard part isn't knowing the number — it's sticking to it. That's where CalShot helps. Snap a photo of your meal and see instantly whether you're on track. No food diary, no barcode scanning, no guessing portion sizes.
BMI is a screening tool, not a diagnosis. Consult a healthcare provider for personalized advice.