Health Calculators
Free health calculators and tests: BMI, calories and macros, biological age, heart risk, blood pressure, sleep and more. Built on published formulas rather than invented scales, and they run right in your browser — nothing is sent to a server.
22 tools, grouped by topic. Each has a short answer above the calculation, a transparent formula with its source, and an honest note on what it can't tell you.
Nutrition
Fitness & Movement
One-Rep Max (1RM) Calculator
Estimate your 1RM from a working set — the average of the Epley, Brzycki and Lombardi formulas plus a table of working weights for every rep goal
Open⏱️Running Pace Calculator
Pace and speed from your distance and time, plus predicted finish times for 5K, 10K, half and full marathon via Riegel's formula
Open💓Heart Rate Zones Calculator
Five zones from your heart rate reserve (Karvonen), adjusted for resting pulse — plus how to split the week
OpenSleep & Recovery
Mental Health
Supplements
Weight & Metabolism
Calorie & Macro Calculator
Your calorie target from Mifflin-St Jeor, split into protein, fat and carbs for your goal and pace
Open⚖️BMI & Body Composition Calculator
BMI, waist, waist-to-height ratio and body fat from a tape measure — four numbers instead of one
Open🎯Ideal Weight Calculator
Your healthy weight range by height and sex — honestly, no single 'ideal' number: the BMI range plus the classic Devine, Robinson, Miller and Hamwi formulas
OpenLongevity
Heart Health
Heart Attack & Stroke Risk Calculator
Your 10-year cardiovascular risk from SCORE2 (2021), calibrated to your region — the current European standard
Open🩺Blood Pressure Category Checker
Which ESC/ESH category your reading falls into — from optimal to hypertension, with the reminder that one reading is not a diagnosis
Open🩸Blood Test Unit Converter
Cholesterol, glucose, triglycerides, HbA1c and more — mmol/L ↔ mg/dL both ways, with reference ranges
OpenGut Health
Women's Health
Period Calculator
Your next period date, current cycle day and upcoming cycles from your last period
Open🤰Pregnancy Weight Gain Calculator
Recommended pregnancy weight gain by the IOM ranges based on your pre-pregnancy BMI, with a weekly pace
Open🌸Ovulation & Cycle Calculator
Your fertile window, ovulation date and the cycles ahead — with the real margin of error instead of one confident date
Open🤰Due Date & Pregnancy Calculator
Your due date from the last period (Naegele's rule), how many weeks along you are today, trimester and key dates — adjusted for cycle length
OpenImmunity
🔒 Your data never leaves your browser
Frequently asked questions
- Are online health calculators accurate?
- Ours use published scientific formulas (Mifflin-St Jeor for calories, Levine PhenoAge for biological age, SCORE2 for cardiovascular risk, and so on), with the source stated under each tool. They're a guide, not a diagnosis: a calculator can't see your full history or replace a doctor.
- Is it free and without sign-up?
- Yes. Every calculator and test is free, no registration is needed, and ads never get in the way of the result.
- Is my data stored?
- No. The maths runs right in your browser — the numbers you enter (weight, height, lab results) are never sent to a server or stored anywhere.
- Do calculators replace a doctor?
- No. They help you understand your numbers and ask better questions, but they don't diagnose or prescribe. See a professional for worrying symptoms.