Free Health Tools & Calculators

Privacy-first calculators and reference guides — nothing you enter is stored. Work in metric or imperial. Educational only; for advice, talk to a verified doctor.

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Body & weight

BMI Calculator

Body Mass Index (BMI) is a simple screening number calculated from your height and weight. This free calculator works in metric and imperial units and shows where your BMI falls on the WHO reference chart.

Ideal Weight

Estimate a healthy weight range for your height using the WHO BMI range plus classic clinical reference formulas (Devine, Robinson, Miller, Hamwi). Works in kg and lb.

Body Fat %

Estimate your body-fat percentage using the U.S. Navy circumference method from a few tape measurements. An estimate for tracking trends — not a clinical body-composition scan.

Waist-to-Height

Waist-to-height ratio (WHtR) is a simple measure of central body fat. Keeping your waist under half your height is a widely used general guideline. Works in cm and inches.

Nutrition & fitness

BMR / Calorie Needs

Your Basal Metabolic Rate (BMR) is the energy your body uses at rest; your Total Daily Energy Expenditure (TDEE) adds your activity. This calculator uses the Mifflin-St Jeor equation to estimate daily calorie needs.

Water Intake

Estimate a general daily water target based on your body weight and activity. A practical rule-of-thumb to support healthy hydration — your needs change with climate, health, and pregnancy.

Heart Rate Zones

Estimate your maximum heart rate and the five training zones (from recovery to maximum effort) based on your age, to guide cardio exercise intensity.

Heart & metabolic

Blood Pressure

Enter a blood-pressure reading to see where it falls on the ACC/AHA reference chart (normal, elevated, hypertension stages). This explains the categories — it does not diagnose high blood pressure.

A1C ↔ Glucose

Convert between HbA1c (%) and estimated average glucose (eAG) using the ADAG formula, and between mg/dL and mmol/L. A reference converter for understanding your own lab results.

Glucose Units

Convert blood glucose readings between mg/dL (used in the US) and mmol/L (used in the UK, EU and most of the world). A simple reference converter.

Pregnancy & fertility

Due Date

Estimate your pregnancy due date and current week from the first day of your last menstrual period (LMP), using Naegele’s rule. An estimate — your clinician’s dating scan is the authoritative date.

Ovulation

Estimate your most fertile days and likely ovulation date from your last period and average cycle length. An estimate based on cycle averages — fertility varies cycle to cycle.

Children

Child & Teen BMI

For children and teenagers (ages 2–19), BMI is interpreted by age- and sex-specific percentiles rather than the adult cut-offs. This calculator shows the BMI value and explains how a clinician reads it against growth charts.

When to see a doctor

Fever — see a doctor?

General guidance on the fever situations that usually warrant medical attention — for adults, children and infants. Educational only; if you are worried, speak to a doctor.

Chest pain — see a doctor?

Chest pain can have many causes, some of them emergencies. This page explains the warning signs that mean you should seek urgent or emergency care, and when to book a consultation.

Headache — see a doctor?

Most headaches are not dangerous, but some patterns are red flags. This page explains the headache warning signs that warrant urgent assessment and when to book a consultation.

Medication reference

Medication Classes

A neutral, educational reference explaining common medication classes — what they are, the general types of conditions they are used for, and common forms. It does not provide dosing or personal medication advice.

Medical disclaimer: These tools provide general health information only and are not a substitute for professional medical advice, diagnosis or treatment. Always consult a qualified doctor about your individual health.