Health tools & calculators

20 free calculators and converters for the measurements that matter most on a lab report or at a check-up. Each tool shows the clinical equation it uses, the guideline its categories come from, and the limitations that apply — and every calculation runs privately in your browser.

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Showing 20 of 20 tools

Waist-to-Height
General Wellness
Divide your waist by your height and read the result against the bands NICE publishes.
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Waist-to-Hip
General Wellness
Compare your waist and hip measurements against the cut-points in the WHO expert consultation.
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Body Fat %
Fitness
Estimate body fat from tape measurements with the Hodgdon–Beckett circumference equations.
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Body Surface Area
General Wellness
Calculate body surface area with four published equations, and see how far apart they land.
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Ideal Body Weight
General Wellness
Compare the Devine, Robinson, Miller and Hamwi equations — and see how much they disagree.
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Creatinine Clearance
Kidney Health
Estimate creatinine clearance with Cockcroft-Gault, and see why it differs from eGFR.
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Cholesterol Converter
Blood Tests
Convert a whole lipid panel between mg/dL and mmol/L, with the correct factor for each value.
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Water Intake
Nutrition
See the US and European reference values for water side by side, rather than one invented number.
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Protein Intake
Nutrition
See the protein RDA and the published ranges for older adults and regular training.
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Macros
Nutrition
Turn a daily calorie figure into grams of carbohydrate, protein and fat inside the published ranges.
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HbA1c to eAG
Diabetes & Metabolic Health
Convert an HbA1c percentage into an estimated average blood glucose.
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Glucose Converter
Diabetes & Metabolic Health
Convert blood glucose between mg/dL and mmol/L in either direction.
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BMI
General Wellness
Calculate body mass index in feet and pounds or metric units, with its real limits explained.
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BMR / TDEE
Nutrition
Estimate basal metabolic rate and total daily energy expenditure.
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Blood Pressure
Heart Health
See which guideline category a blood pressure reading falls into.
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Pulse Pressure & MAP
Heart Health
Calculate pulse pressure and estimated mean arterial pressure from a blood pressure reading.
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Cholesterol Ratio
Heart Health
Calculate your total-cholesterol-to-HDL ratio and non-HDL cholesterol.
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LDL
Heart Health
Calculate LDL cholesterol with the NIH Equation 2 or Friedewald method.
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Heart Rate Zones
Fitness
Estimate training heart rate zones from your age and optional resting heart rate.
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eGFR
Kidney Health
Estimate kidney filtration rate with the race-free CKD-EPI 2021 equation.
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Medical disclaimer. Gravis Labs provides general educational information and calculation tools. Results may be estimates and are not a medical diagnosis or a substitute for professional medical advice, clinical examination, clinical judgment, or treatment.

In an emergency. Do not use Gravis Labs for medical emergencies. If you believe you are experiencing a medical emergency, contact your local emergency services or seek urgent medical care.

Scope. Gravis Labs is an information and calculation service. It is not a medical device, and it is not registered, approved, certified or cleared by any medical regulator or health authority. Nothing here carries clinical authority: every result is an estimate produced by a published equation, and anything that matters for your health needs the opinion of a qualified clinician who can examine you and see your full history.

Read the full medical disclaimer.