Yes, for most adults BMI is still a useful screening tool because it gives a fast rough check of whether body weight is low, moderate or high relative to height. It is not a diagnosis and it works best when used with other measures like waist circumference, body fat estimate, fitness, blood pressure and blood test results.

What should you use alongside BMI?

Waist circumference is one of the most practical extra checks because abdominal fat is strongly linked with health risk. A body fat estimate, your BMR or TDEE for planning nutrition, and clinical markers like blood pressure, cholesterol and glucose can also give a clearer picture than BMI alone.

Why can BMI be misleading?

BMI does not show the difference between fat mass and muscle mass, and it does not show where body fat is stored. That means very muscular people can look heavier on BMI than their health picture suggests, while some people can have a BMI in the usual range but still carry higher-risk abdominal fat.

BMI Is Flawed, But Here's Why It's Still Useful (and What to Use Alongside It)

August 21, 2026 • 6 min read

Person exercising in a gym, representing health measurements beyond BMI

BMI gets mocked a lot online. Fair enough too. It is a blunt tool. It cannot tell the difference between muscle and fat, it says nothing about fitness, and it definitely cannot see that you can deadlift a small hatchback.

But people go too far the other way and act like BMI is completely useless. It is not. For most adults, it is still a decent first-pass screening tool. The problem is not BMI existing. The problem is pretending it should do a job it was never built to do.

This guide explains where BMI helps, where it falls over, and what to use alongside it if you want a more realistic view of your health. If you want to run your own numbers, start with our BMI Calculator, then check your Body Fat Calculator and BMR Calculator.

Quick takeaway
BMI is useful for screening, not diagnosing. For most adults, the smartest move is to use BMI together with waist circumference, a body fat estimate, and practical markers like fitness, blood pressure, cholesterol and blood sugar.

What BMI actually is

BMI stands for body mass index. It is calculated as weight in kilograms divided by height in metres squared.

That is it. No secret sauce. No complicated physiology hiding behind the curtain. Just a ratio.

For adults, the usual cut-offs are:

Underweight: below 18.5
Healthy range: 18.5 to 24.9
Overweight: 25 to 29.9
Obesity: 30 and above

These categories are widely used in Australia and internationally as a population-level screening tool. That word matters: screening. BMI helps identify whether someone might have higher health risk and might benefit from a closer look. It does not diagnose health, fitness, or how you look in bathers.

Why BMI is still useful

The biggest strength of BMI is that it is quick, cheap, and reasonably useful at scale. A GP, public health service, or research study can use it fast across large numbers of people. For the average adult, higher BMI often does track with higher risk of conditions like type 2 diabetes, heart disease, sleep apnoea and high blood pressure.

That does not mean every individual with a high BMI is unhealthy, or every individual with a lower BMI is healthy. It just means BMI is often directionally useful.

Think of it like a smoke alarm. A smoke alarm is helpful even though it cannot tell you whether the smoke came from a house fire or somebody murdering toast. BMI works in a similar way. It flags something worth checking, not the full story.

Where BMI falls short

1. It cannot separate muscle from fat

If two people are the same height and weight, they get the same BMI even if one has much more muscle and the other has much more body fat. That is the classic complaint, and it is valid.

This matters most for people who carry above-average muscle mass, like some athletes, lifters, and very active workers. BMI can make them look worse on paper than they really are.

2. It says nothing about fat distribution

Where fat is stored matters. Carrying more fat around the abdomen is generally linked with higher cardiometabolic risk than carrying more around the hips and thighs. BMI does not know the difference.

That is why waist circumference is so useful alongside BMI. In Australian health guidance (sourced from Healthdirect and the Victorian Better Health Channel), waist measurements above roughly 94 cm for men and 80 cm for women suggest increased health risk, while above 102 cm for men and 88 cm for women suggest substantially increased risk. These are broad adult guideposts, not moral verdicts, and they do not apply universally to children, pregnant people, or some non-European backgrounds. Check with a GP if you are unsure how to interpret your number.

3. It misses some people with normal-weight risk

A person can land in the usual BMI range and still have low muscle mass, high abdominal fat, poor fitness, raised blood pressure, or concerning blood test results. This is one reason health professionals do not stop at BMI alone.

4. It is not equally informative in every context

BMI has limits for children, teenagers, pregnant people, older adults, and some ethnic groups. Kids use age- and sex-specific growth references rather than the plain adult cut-offs above. Older adults may have lower muscle mass, which changes how the number should be interpreted. Clinical context matters.

What to use alongside BMI

If you want a more useful picture, here are the extras that actually help.

Waist circumference

This is probably the most practical add-on. It is simple, cheap, and gets closer to the abdominal fat question that BMI misses. Measure around your waist consistently, ideally at the same point each time, and look at the trend rather than obsessing over one millimetre because your tape measure was feeling dramatic.

Body fat estimate

A body fat estimate gives more detail than BMI, even if home methods are not perfect. Skinfolds, BIA smart scales, calipers and formulas all have limitations, but they still tell you more about composition than height and weight alone. Our Body Fat Calculator is a good next step if BMI has left you a bit unconvinced.

BMR and TDEE

If your goal is weight change, energy planning matters more than arguing with BMI on the internet. Your BMR Calculator estimates baseline energy needs, and your TDEE Calculator helps estimate daily calorie burn once activity is included.

These are still estimates, but they are practical estimates. They help answer, "what should I do next?" which is usually a more useful question than "is BMI rude?"

Fitness and health markers

Resting blood pressure, blood glucose, cholesterol, aerobic fitness, strength, sleep, and how you actually function day to day matter a lot. If those markers are improving, that is real progress even if your BMI moves slowly or sits in a range you do not love.

When BMI is especially helpful

You want a simple starting point. It gives you a quick check without special equipment.
You are tracking a long-term trend. BMI can be more useful over time than as a one-off number.
You need a basic screening metric. That is literally what it is for.
You are pairing it with other data. This is where it shines most.

If you are a pretty average adult with no unusual edge case, BMI is often a helpful signal. Not the whole dashboard, just one gauge on it.

When BMI can be more misleading

You carry a lot of muscle.
You are older and have lost muscle mass.
You are pregnant.
You are assessing a child or teen using adult cut-offs.
You use the number as a diagnosis instead of a prompt for more context.

That last one is the biggie. People do not get into trouble because BMI exists. They get into trouble because they over-trust one number and ignore everything else.

A better way to think about it

Here is the simple version.

Use BMI as a screening tool.
Check waist circumference for abdominal fat risk.
Use a body fat estimate if composition is the real question.
Use BMR and TDEE if your goal is changing weight or performance.
Pay attention to clinical markers and how you feel, not just one ratio.

That is a much saner system than either blindly trusting BMI or throwing it in the bin because a shredded rugby player once scored as overweight.

The bottom line

BMI is flawed. Completely agree. But it is still useful because most screening tools are allowed to be simple. They just are not allowed to pretend they are the whole answer.

If your BMI is outside the usual range, treat that as a cue to look deeper, not panic. If your BMI is inside the usual range, do not assume you are automatically in the clear either. Waist measurement, body composition, activity, fitness and clinical markers matter too.

The best health number is usually not one number. Slightly annoying, I know.

FAQ

Is BMI accurate for muscular people?

Not always. BMI can overestimate risk in people with above-average muscle mass because it reads total body weight, not body composition. That is why body fat and waist measurement help.

Should I ignore BMI if my waist is healthy?

Not necessarily. A healthier waist measurement is a good sign, but BMI can still be useful as one part of the picture. Use both together rather than setting them up for a cage fight.

What is better than BMI?

Nothing replaces everything on its own. A better setup is BMI plus waist circumference, body fat estimate, and health markers like blood pressure, glucose and cholesterol.