How to read your BMI
BMI takes your weight and height and boils them down to a single number. It is meant as a quick screen — a way to see roughly where you sit and whether a closer look might be worth it. Here is how the standard categories break down for adults.
| BMI | Category | What it suggests |
|---|---|---|
| Below 18.5 | Underweight | May point to under-nutrition or an underlying issue worth checking. |
| 18.5 – 24.9 | Normal weight | The range generally linked with the lowest health risk. |
| 25 – 29.9 | Overweight | Slightly raised risk for some conditions; context matters a lot. |
| 30 and above | Obese | Higher risk; a good prompt for a conversation with a doctor. |
Two people with the same BMI can be in very different health. The number is a starting point for a conversation, not the conversation itself.
What a healthy weight looks like for your height
Because BMI depends on height, the "healthy" weight range shifts as you get taller. The calculator above does this automatically — enter your height and it shows the weight range that lands you in the 18.5–24.9 band. As a feel for it, someone 1.70 m tall has a healthy range of roughly 53–72 kg; at 1.85 m that rises to about 63–85 kg.
Why waist-to-height ratio is worth a look
One of BMI's blind spots is that it cannot see where you carry weight, and fat around the middle carries more risk than fat elsewhere. That is why the Body Metrics tab also gives your waist-to-height ratio. The rule of thumb could not be simpler: keep your waist under half your height. A ratio below 0.5 is the goal, and for a lot of people it is a better everyday signal than BMI alone.
Where BMI gets it wrong
It is worth being honest about the limits, because they are real:
It can't tell muscle from fat
Muscle is dense, so very fit, muscular people can read as "overweight" while carrying little fat. The number is missing that context.
It ignores fat distribution
Two people at the same BMI can have very different risk depending on where the weight sits. Waist measurement fills that gap.
It was built on a narrow group
BMI was modelled mostly on European adults, so it can misjudge older people, athletes, and different ethnic backgrounds.
Frequently asked questions
Is BMI accurate?
For populations, it is a reasonable screen. For any single person it is a rough guide — useful alongside other signals like waist size, fitness and how you feel, not a verdict on its own.
What is a healthy BMI?
For most adults, 18.5 to 24.9 is the range associated with the lowest health risk. Below or above that is a prompt to look a little closer, not a reason to panic.
Does BMI work for athletes?
Often not well. A muscular athlete can have a high BMI with low body fat. For very active or muscular people, body-fat measures and waist ratio give a truer picture.
Does BMI differ for men and women?
The BMI calculation and adult categories are the same for both. Body composition does differ between sexes, which is one more reason to read the number with context.
Is this BMI calculator free?
Yes — free, no signup, and your measurements are never stored. Use it as often as you like.