Health calculators
Run the numbers — and understand them.
Free calculators that don't just give you a number. Each one shows where your result falls on a clear visual scale and explains, in plain language, what it means and what to consider next. Nothing is saved.
- Body composition BMI calculator Estimate your body mass index from your weight and height, and see what the number means in plain language — with the usual caveats about what BMI can and cannot tell you. Open calculator
- Calories and energy TDEE calculator Your total daily energy expenditure (TDEE) is the number of calories you burn in a day, and eating that many keeps your weight about where it is. Enter your sex, age, height, weight and how active you are: the calculator estimates your resting burn with the Mifflin-St Jeor equation, multiplies it by an activity factor from the FAO/WHO/UNU energy report, and shows the result with its margin of error. Open calculator
- Weight and height Ideal weight calculator Enter your height to see the weight range the World Health Organization counts as healthy for it, a BMI of 18.5 to 24.9. Below it you will find the four classic "ideal body weight" formulas (Devine, Robinson, Miller and Hamwi) for comparison, with an explanation of where they come from and why a range is the more useful answer. Open calculator
- Body composition Body fat calculator Estimate your body fat percentage from a tape measure: neck and waist for men, neck, waist and hips for women, plus your height. The calculator uses the US Navy circumference equations and compares the result with healthy body fat ranges for your sex and age from a peer-reviewed study that linked body fat to the BMI cut-offs. Open calculator
- Heart & circulation Blood pressure category Enter a systolic and diastolic reading to see where it falls on the ACC/AHA blood pressure chart, with a plain-language explanation of what that category means. Open calculator
- Blood sugar HbA1c to average glucose Convert your HbA1c percentage into an estimated average glucose (eAG) in mg/dL and mmol/L, and see how the value maps onto the normal, prediabetes, and diabetes ranges. Open calculator
- Heart & metabolic risk Cholesterol ratio Work out your total-cholesterol-to-HDL ratio and your non-HDL cholesterol from your lipid panel, and see how the ratio fits into cardiovascular risk — with the caveat that it is only one piece. Open calculator
- Kidney function eGFR calculator Estimate your glomerular filtration rate from your creatinine, age, and sex using the race-free CKD-EPI 2021 equation, and see the corresponding kidney-function stage explained. Open calculator
- Kidney function Creatinine clearance calculator Estimate creatinine clearance from age, sex, body weight, and serum creatinine using the Cockcroft-Gault equation, the formula much drug-dosing guidance is still written against. Open calculator
- Metabolism Corrected calcium calculator Adjust a total serum calcium for a low or high albumin using the Payne formula, and see how the corrected figure compares with the standard reference range. Open calculator
- Metabolism Anion gap calculator Calculate the serum anion gap from sodium, chloride, and bicarbonate, with an optional albumin correction, and see how the result is used to work up a metabolic acidosis. Open calculator
- Liver FIB-4 calculator Estimate the FIB-4 index from age, AST, ALT, and platelet count, with the age-adjusted lower cutoff applied automatically, and see how the score is used to triage advanced liver fibrosis. Open calculator
- Kidney function BUN/creatinine ratio calculator Enter the BUN (blood urea nitrogen) and creatinine from your blood test to get the BUN to creatinine ratio, see where it sits against the usual 10 to 20 range, and read what a high or low ratio can and cannot tell you. The ratio carries most meaning when one or both values are abnormal; when both are normal, it says little. Open calculator
- Metabolism HOMA-IR calculator Enter fasting glucose and fasting insulin from the same blood draw to calculate your HOMA-IR score, then see where it sits against the cutoffs published in research studies. Open calculator
- Heart & circulation QTc calculator Enter the QT interval and heart rate printed on an ECG report to get the corrected QT interval (QTc) by four formulas: Fridericia, Bazett, Framingham and Hodges. The result is compared with the normal QTc limits for men and women. This tool works from a number someone has already measured; it cannot measure QT from a tracing. Open calculator
- Body composition Waist-to-hip ratio calculator Divide your waist measurement by your hip measurement to get your waist-to-hip ratio, then compare it with the World Health Organization thresholds of 0.90 for men and 0.85 for women. The guide below shows exactly where to put the tape, because the measurement decides how useful the number is. Open calculator
- Heart & metabolic risk LDL cholesterol calculator Estimate your LDL cholesterol from total cholesterol, HDL and triglycerides with the NIH (Sampson) equation, compare it with the older Friedewald formula, and see where the result sits in the standard LDL categories. Open calculator
- Heart & cardiovascular risk SCORE2 calculator Estimate your 10-year risk of a heart attack or stroke (fatal or non-fatal) with the European Society of Cardiology (ESC) models for people without cardiovascular disease: SCORE2 for ages 40-69 and SCORE2-OP for ages 70-89. Choose the risk region of the country you live in, then see which ESC 2021 risk category the result falls into for your age. The figure is a population estimate to discuss with a clinician. It does not decide treatment. Open calculator
- Heart & circulation PREVENT calculator Estimate your 10-year risk of cardiovascular disease with the American Heart Association PREVENT equations (2023). Enter your age, cholesterol, blood pressure and kidney function (eGFR), and answer four yes-or-no questions. The headline is total cardiovascular disease, which combines heart attack, stroke and heart failure; your 10-year ASCVD risk (heart attack and stroke) is shown with it. PREVENT is for adults aged 30 to 79 who have never had a heart attack, stroke or heart failure. Open calculator
- Heart & circulation ASCVD risk calculator Estimate your 10-year risk of a first heart attack or stroke with the 2013 ACC/AHA Pooled Cohort Equations, the equations behind the ACC ASCVD Risk Estimator. Enter your age, cholesterol and blood pressure and answer a few yes-or-no questions; the result is placed in the low, borderline, intermediate or high risk category used by US guidelines. It is for adults aged 40 to 79 who have never had a heart attack or stroke. The newer AHA PREVENT equations are available too, in the PREVENT calculator on this site. Open calculator
- Children and teens Child BMI calculator Enter a child or teen’s age, sex, height and weight to get their BMI, their BMI-for-age percentile on the CDC growth charts, and the weight category it falls in. Open calculator
- Sleep Sleep calculator Pick the time you need to wake up, or the time you are going to bed, and get bedtimes or wake-up times that fit 4, 5 or 6 full sleep cycles of about 90 minutes, plus the minutes it takes you to fall asleep. Adults are advised to sleep 7 hours or more, which means 5 or 6 cycles for most people. Open calculator
- Heart & circulation Mean arterial pressure (MAP) calculator Enter a systolic and diastolic blood pressure reading to calculate the mean arterial pressure (MAP), the average pressure in your arteries over one heartbeat, along with the pulse pressure. A MAP of 70 to 100 mmHg is the range generally considered normal. Open calculator
- Metabolism Serum osmolality calculator Calculate serum osmolality from sodium, glucose and BUN (or urea), in US or SI units. Add a measured osmolality from your lab report to get the osmolal gap. The usual reference range for serum osmolality is 275 to 295 mOsm/kg. Open calculator
- Lung health Pack-year calculator Enter how many cigarettes (or packs) you smoked per day and for how many years to get your smoking history in pack-years. One pack-year is 20 cigarettes a day for one year. Doctors use the number to decide who should be offered lung cancer screening: in the US, 20 pack-years is the threshold. Open calculator
- Nutrition Protein intake calculator Enter your weight, age and how active you are to see how many grams of protein a day the published recommendations point to for you. The figures come from the US Recommended Dietary Allowance, the sports nutrition position statements and the PROT-AGE recommendations for people over 65, all set in grams per kilogram of body weight. Open calculator
- Body measurements BSA calculator Enter height and weight to get body surface area (BSA) in square metres by the Mosteller formula, with the Du Bois and Haycock results beside it. The page also shows each formula, a worked example and a table comparing the three, so you can check a number by hand. Open calculator
- Pregnancy Pregnancy weight gain calculator Enter your weight before pregnancy, your height and how many weeks pregnant you are. The calculator works out your pre-pregnancy BMI and shows the total weight gain the Institute of Medicine (IOM) recommends for it, plus the range that is typical by your current week. These are ranges to discuss with your midwife or doctor, who know how your pregnancy is going. Open calculator
- Pregnancy Due date calculator Enter the first day of your last period and your usual cycle length to estimate your due date, how far along you are today and when each trimester begins. The calculator uses the same last-period method obstetricians use, and an early ultrasound takes over whenever the two dates disagree. Open calculator
- Cycle and fertility Ovulation calculator Enter the first day of your last period and your usual cycle length to see your estimated ovulation day, your fertile window and when your next period is due, with the same dates for the next two cycles. It is a calendar estimate built on averages, useful for planning and unreliable as birth control. Open calculator
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This is general health information, not a diagnosis. Reference ranges vary by laboratory and by person — use the values on your own report and talk to a clinician about what they mean for you.