Health
Health calculators for weight, lab values and training
BMI, calories and macros, eGFR from creatinine, body surface area, dosage by weight, blood pressure, pregnancy, VO2max and caffeine. Not medical advice.
The everyday half of the section: BMI, calorie and macro targets, body fat, water, heart rate zones, sleep and a rough guide to when alcohol clears — the things worth checking yourself.
The clinical half sits closer to the numbers on a chart: eGFR by CKD-EPI, body surface area, lean mass, dosing by weight, blood pressure categories, pregnancy weight gain and the corrected age of a preterm baby.
Tools in this category
When can I drive after drinking?
Estimate blood alcohol concentration from drinks, body weight and time elapsed using the Widmark formula. An estimate only — never a driving decision.
BMI Calculator
Calculate body mass index from height and weight, with the WHO categories and an honest explanation of where BMI stops being useful.
Daily Calorie Intake Calculator
Estimate daily calorie needs from the Mifflin-St Jeor equation and your activity level, with targets for losing or gaining weight.
BMR Calculator
Calculate basal metabolic rate with the Mifflin-St Jeor equation. This is the floor of your daily energy use, before any activity.
Body Fat Percentage Calculator
Estimate body fat percentage from neck, waist and hip measurements. More informative than BMI, and still only an estimate.
Ideal Weight Calculator
Compare the Devine, Robinson, Miller and Hamwi estimates for your height. The spread between them is the real lesson.
Macro Calculator
Split your calorie target into grams of protein, carbohydrate and fat, with ratios adjusted for your goal.
Water Intake Calculator
Work out roughly how much water to drink per day from body weight, activity and climate. A starting figure, not a medical rule.
Pregnancy Due Date Calculator
Estimate a due date from the first day of your last period, adjusted for cycle length, plus how many weeks along you are today.
Heart Rate Zone Calculator
Calculate maximum heart rate and five training zones using the Karvonen method, which accounts for your resting heart rate.
Sleep Calculator
Find what time to go to bed or wake up so your alarm falls between 90-minute sleep cycles rather than in the middle of deep sleep.
Ovulation Calculator
Estimate the likely day of ovulation and the fertile window around it, based on cycle length and the luteal phase.
Running Pace Calculator
Convert a run into pace per kilometre and mile, or predict a finish time from a target pace over any distance.
One Rep Max Calculator
Estimate a one-rep max from a set you have actually completed, with Epley and Brzycki shown separately, plus training percentages.
Dog Age Calculator
A dog's age in human terms adjusted for breed size, the life stage it corresponds to and typical life expectancy.
Cat Age Calculator
A cat's age in human terms, the life stage it corresponds to and life expectancy indoors versus outdoors.
GFR Calculator
Works out estimated GFR with the CKD-EPI 2021 equation and creatinine clearance with Cockcroft-Gault, gives the CKD stage, and converts creatinine between units.
Body Surface Area Calculator
Works out body surface area with four equations at once — Mosteller, Du Bois, Haycock and Gehan-George — and shows the spread between them.
Lean Body Mass Calculator
Works out lean body mass with the Boer, James and Hume equations and derives an estimated body fat percentage from it.
Waist to Hip Ratio Calculator
Works out waist-to-hip and waist-to-height ratios, compares them against WHO thresholds, and assesses waist circumference on its own.
Protein Intake Calculator
Works out a daily protein target from body weight and training load, splits it across meals, and shows the share of total calories it represents.
Calories Burned Calculator
Works out the calories a session burns using metabolic equivalents, adjusted for body weight and duration.
Caffeine Half-Life Calculator
Works out how much caffeine is left after a given number of hours and when the level falls below the point that interferes with sleep.
Blood Pressure Categories Calculator
Places a blood pressure reading into its category under both European and American guidelines, and works out pulse and mean arterial pressure.
Dosage by Weight Calculator
Works out a single and daily dose from body weight, converts it into millilitres of a liquid formulation, and checks it against a daily cap.
Pregnancy Weight Gain Calculator
Compares actual weight gain against the IOM recommendations for your gestational week and your pre-pregnancy body mass index.
Baby Age Calculator
Works out a baby's age in months, weeks and days, and gives a corrected age for babies born before term.
VO2max Calculator
Estimates maximal oxygen uptake three ways: from the Cooper test, from resting heart rate, and from a 2.4 kilometre time trial.
Menstrual Cycle Calendar
Works out the dates of the next periods, the likely day of ovulation and the fertile window from the last period and the cycle length.
Smoking Cost Calculator
Works out what smoking costs a day, a month and a year, how much has gone in total, and what the same money would have become in a savings account.
Barbell Plate Calculator
Works out which plates to load on each side of the bar for a target weight, and whether that weight loads exactly.
Wilks Coefficient Calculator
Works out Wilks points from bodyweight and total, so lifters in different weight classes can be compared.
Steps to Kilometres Calculator
Converts steps into kilometres with an adjustment for height, and works out what the walk cost in calories.
Race Time Predictor
Predicts a time over a longer distance from a result at a shorter one, using Riegel's formula.
Swim Pace Calculator
Works out pace per hundred metres, speed and time per length from a distance and a total time.
Cycling Power and Speed Calculator
Links watts to kilometres an hour, accounting for mass, gradient, rolling resistance and aerodynamics.
Weight Loss Timeline Calculator
Works out how many weeks a weight target takes at a chosen calorie deficit, and whether the rate is safe.
TDEE Calculator
Works out total daily energy expenditure with the Mifflin-St Jeor equation and an activity multiplier.
Training Max Calculator
Builds a table of working weights as percentages of a one-rep max, rounded to the plates you actually have.
Pace to Speed Converter
Converts minutes per kilometre into kilometres an hour and back, and gives the resulting 5K and marathon times.
Related categories
FAQs
What tools are in the Health category?+
BMI, BMR, calorie intake, body fat, ideal weight and macros, plus eGFR, body surface area, lean mass, waist ratios, protein targets, calories burned, caffeine, blood pressure, dosing by weight, pregnancy weight gain, baby age, VO2max, cycle dates and the cost of smoking.
Can I use the result as medical advice?+
No. These are estimate-based tools meant for orientation only.
Who is this category useful for?+
Anyone who wants a fast personal estimate without manually applying formulas.
Does each calculator have its own page?+
Yes. Every tool has a dedicated route with its own SEO block.