Health Calculators
Five screening calculators built on published, widely used equations. They give a quick, private estimate from a tape measure and a scale. They are a starting point for a conversation with a clinician, not a diagnosis.
5 calculators · Last reviewed September 26, 2026
The calculators
BMI Calculator
Body mass index with the WHO adult categories
Macro Planner
Daily calories and protein, carb and fat targets
Body Fat %
U.S. Navy tape-measure body fat estimate
Waist-Hip Ratio
Waist-to-hip ratio against WHO risk thresholds
Waist-to-Height Ratio
A quick belly-fat risk check, compared with BMI
Which calculator answers your question?
Is my weight in a healthy range for my height?
BMI CalculatorRoughly what percentage of my body is fat?
Body Fat %Does where I carry weight put me at higher risk?
Waist-Hip RatioHow many calories and grams of protein should I eat a day?
Macro PlannerKey ideas behind these calculators
BMI is a population screen
BMI is weight in kilograms divided by height in meters squared. The World Health Organization adult bands are under 18.5 (underweight), 18.5 to 24.9 (healthy), 25 to 29.9 (overweight) and 30 or more (obesity). BMI cannot tell muscle from fat, so athletes and older adults are often misclassified.
Where fat sits matters
Fat around the abdomen is more closely linked to heart disease and type 2 diabetes than total weight. The WHO flags a waist-to-hip ratio above 0.90 in men and above 0.85 in women as substantially increased risk.
Tape-measure body fat
The U.S. Navy method estimates body fat from height and neck, waist (and, for women, hip) measurements. It is practical and repeatable, which makes it good for tracking change over time, but it is less precise than a DEXA scan.
Energy needs are estimates
The Macro Planner uses the Mifflin-St Jeor equation for resting metabolism, then an activity multiplier. Real needs vary by a few hundred calories either way. Adjust based on how your weight actually changes over several weeks.
What these estimates leave out
- Children and teens. Under 20, BMI must be read against age- and sex-specific percentiles.
- Pregnancy, eating disorders, and medical conditions that affect weight or metabolism.
- Ethnicity. Some populations carry higher risk at lower BMI and waist cut-offs than the general bands shown.
- Diagnosis or treatment. See a doctor or registered dietitian before acting on a result.
See the full disclaimer and how we build and check the calculators.
Health guides
All guidesWaist-to-Height Ratio vs BMI: What Each One Tells You
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How Sleep Affects Fat Loss and Appetite
Short sleep is linked to eating more and losing less fat on a diet. What the studies found, a worked calorie example, and how much sleep adults need.
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