What is a body assessment?

It's a set of measurements and calculations that describe a person's body composition and energy expenditure: weight, height, BMI, body fat percentage, lean mass percentage, basal metabolic rate (BMR), total daily energy expenditure (TDEE), and waist-to-hip ratio (WHR). It serves as a starting point for prescribing workouts and diet, and for tracking progress.

How does the generator calculate body fat percentage?

We use the U.S. Navy method, which estimates body fat percentage from neck, waist, and hip measurements (women) or neck and waist (men), plus height. It's a validated method that requires no calipers or bioimpedance scale — useful as an initial reference.

Is the fitness assessment really free?

Yes. 100% free, no sign-up required, and no usage limits. The calculation runs right in your browser, and nothing is sent to our servers. You can download the results as a PDF at the end.

Can I use it as a personal trainer with my clients?

Feel free to use it as a support tool. But to log your clients' assessments, build progress history, generate evolution charts, and use AI-powered body analysis (body fat % estimate from a photo), use the Trainer Connect app — built specifically for personal trainers.

Which measurements do I need on hand?

Weight (lbs), height (in), age, sex, and neck, waist, and hip measurements (in inches). All measured with a simple tape measure. For a more accurate body fat %, measure fasted, unclothed, and always at the same time of day.

Free Online Fitness Assessment with PDF

1 Personal data

Biological sex

Male Female

Age (years)

Activity level

Weight (lbs)

Height (cm)

2 Body measurements

Measure with a relaxed tape measure, in cm. Neck just below the Adam's apple. Waist at navel height. Hips at the widest part.

Neck (in)

Waist (cm)

Hips (cm) — required for women, optional for men (WHR)

Your assessment will appear here

Fill in the personal data e body measurements next to it, and click Generate complete assessment to see:

Body fat percentage
Lean mass vs. fat mass
BMI and WHO classification
BMR (basal metabolic rate)
TDEE (total daily energy expenditure)
WHR (waist-to-hip ratio)
Personalized interpretation

Next step

Want an assessment 100x more accurate and in photos?

Trainer Connect has AI body analysis: the trainer takes 3 photos of the client (front, back, side) and Claude's AI (Anthropic) estimates body fat %, lean mass %, somatotype (ecto/meso/endo), posture and muscle asymmetries. No skinfold calipers, no bioimpedance, in seconds.

3 photos = a complete assessment AI estimates body composition and posture.

Automatic history and charts See the progress of each measurement over time.

Professional PDF for your client Complete assessment with your brand and logo.

Share with a nutritionist The client downloads the PDF and brings it to their session.

Start for free on the app Explore the AI →

Are you a personal trainer? On personal trainer software each client's assessment stays in their history, alongside workouts, schedule, and billing. Free for 1 client.

How each metric works

Validated formulas and world-renowned references used by trainers and nutritionists.

BMI

Body Mass Index — weight ÷ height². Classification WHO. A quick indicator, but it doesn't distinguish muscle from fat.

% Body Fat

Method U.S. Navy (US Navy Body Fat). Uses neck, waist, hip (for women), and height. Validated and widely used.

BMR and TDEE

BMR by formula Mifflin-St Jeor (more accurate than Harris-Benedict). TDEE = BMR × activity factor.

WHR

Waist-to-Hip Ratio. Measures fat distribution. Cardiovascular risk indicator according to the WHO.

Body fat percentage chart

Reference ranges by sex (American Council on Exercise — ACE).

Classification	Men	Women
Essential	2 – 5%	10 – 13%
Athletic	6 – 13%	14 – 20%
Fitness	14 – 17%	21 – 24%
Acceptable	18 – 24%	25 – 31%
Obesity	25% or more	32% or more

Frequently asked questions

Is the calculation reliable?

We use validated formulas: Mifflin-St Jeor (BMR), U.S. Navy (body fat %) and classification WHO (BMI/WHR). It's a good estimate for tracking progress, but for clinical purposes always complement it with bioelectrical impedance or a DEXA scan performed by a professional.

Why do they ask for neck and waist measurements?

The US Navy method estimates body fat percentage using these circumference measurements as a proxy for fat tissue. For women, the hip measurement is also factored in because fat distribution differs.

How do you measure it correctly?

Use a simple measuring tape, parallel to the floor, without pulling tight. Neck: just below the Adam's apple. Waist: at belly button height, exhaling normally. Hips: at the widest part (hips). Do it fasting, without clothes, always at the same time.

Can I compare it with my trainer's assessment?

You can, but keep in mind that each method has its own margin of error: skinfold calipers, bioelectrical impedance, and tape measurements will all give slightly different results. What matters is using the same method every time to track progress.

Is the data saved?

No. The entire assessment runs in your browser — no data is sent to our servers. To save results and generate history and progress charts, use the Trainer Connect app (free to get started).

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This assessment is an informational tool and does not replace a medical, nutritional, or professional physical education evaluation. For workout prescriptions, diet plans, or treatment of any health condition, consult a qualified professional.

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