Fitness and Health Calculators
Free health calculators for BMI, calories, body fat, BMR, ideal weight, and pregnancy. Understand your numbers with clear explanations.
26 tools in 4 groups
Most popular
- BMI CalculatorCalculate your body mass index from your height and weight, see the WHO category it falls into, and get the healthy weight range for your height — plus BMI Prime, the Ponderal Index, and how the number is read for children and teenagers.
- Calorie CalculatorEstimate how many calories you burn each day and what to eat to maintain, lose, or gain weight — choose from three BMR equations, six activity levels, and results in calories or kilojoules, with reference tables for common foods, exercise, and food energy.
- Body Fat CalculatorEstimate your body fat percentage with the US Navy circumference method — just a tape measure — and see your fat mass, lean mass, the ideal body fat for your age, how far you are from it, and how a BMI-only estimate compares.
- Body Surface Area CalculatorCalculate body surface area from height and weight. BSA is the size measure medicine uses for chemotherapy doses, cardiac index and kidney function, because it tracks metabolic rate better than weight alone. The calculator gives four standard formulas in square metres and square feet, with the ratio to the 1.73 m² reference adult.
Fitness & Body
- BMI CalculatorCalculate your body mass index from your height and weight, see the WHO category it falls into, and get the healthy weight range for your height — plus BMI Prime, the Ponderal Index, and how the number is read for children and teenagers.
- Body Fat CalculatorEstimate your body fat percentage with the US Navy circumference method — just a tape measure — and see your fat mass, lean mass, the ideal body fat for your age, how far you are from it, and how a BMI-only estimate compares.
- Ideal Weight CalculatorCompare the four standard ideal body weight formulas for your height and sex, alongside the healthy weight range implied by BMI.
- One Rep Max CalculatorEstimate the most you could lift once from a set you have actually done. Enter the weight and the reps, and six standard formulas give your one-rep max, averaged into one figure, along with the training weights for every rep range from 1 to 12 — so you can program percentages without testing a true max.
- Lean Body Mass CalculatorEstimate how much of your weight is not fat. Lean body mass — muscle, bone, organs, water — is what your metabolism and protein needs actually depend on. Enter height, weight and sex for three formula estimates, or add a measured body fat percentage for the exact figure.
- Healthy Weight CalculatorSee the weight range considered healthy for your height. The calculator converts the BMI healthy band (18.5–24.9) into pounds or kilograms for you, shows where your current weight falls and how much change would reach the range, and lists every BMI category as a weight so the whole scale is in familiar units.
- Target Heart Rate CalculatorFind the heart rate to train at. Enter your age for an estimated maximum heart rate and the five standard training zones, or add your resting heart rate to use the Karvonen method, which fits fit people better. The result includes moderate and vigorous ranges: the American Heart Association's percentages of maximum heart rate, or, with a resting heart rate, the American College of Sports Medicine's percentages of heart-rate reserve.
- Height Prediction CalculatorEstimate adult height from parents’ heights using the rough mid-parental method, with metric and inch inputs.
- Army Body Composition CalculatorCalculate the Army’s current waist-to-height ratio from recorded measurements, with three-decimal truncation and the 0.550 threshold.
Nutrition & Energy
- Calorie CalculatorEstimate how many calories you burn each day and what to eat to maintain, lose, or gain weight — choose from three BMR equations, six activity levels, and results in calories or kilojoules, with reference tables for common foods, exercise, and food energy.
- BMR CalculatorCalculate your basal metabolic rate — the calories your body uses at complete rest — with the Mifflin-St Jeor, revised Harris-Benedict, and Katch-McArdle equations, then see your daily need at every activity level in calories or kilojoules.
- TDEE CalculatorFind how many calories you burn in a day. TDEE — total daily energy expenditure — is your basal metabolic rate scaled up for how active you are, and it is the number every diet or bulk is planned around. Enter your details and activity to get your maintenance calories and a ladder of targets for losing or gaining at different rates.
- Macro CalculatorTurn a calorie target into grams of carbohydrate, protein and fat. Start from your body and activity — the calculator works out your calories for losing, maintaining or gaining — or from a calorie number you already have, pick a split or set your own percentages, and get daily and per-meal grams.
- Protein CalculatorWork out how much protein to eat each day. Recommendations range from the 0.8 g per kilogram minimum for healthy adults to over 2 g per kilogram for people cutting fat while training hard. Enter your weight and goal for a daily target in grams, split across your meals and shown as real food.
- Calories Burned CalculatorEstimate total and above-resting calories from activity intensity, body weight and duration, using MET values.
- Carbohydrate CalculatorConvert a daily calorie budget and carbohydrate percentage to grams, with the adult reference range alongside your chosen allocation.
- Fat Intake CalculatorConvert a calorie budget into daily fat grams and compare the selected allocation with the adult reference range.
Pregnancy & Fertility
- Due Date CalculatorEstimate your due date from the first day of your last period, a conception date, an IVF transfer date, or a dated ultrasound — with today's gestational age, the trimester boundaries, and the early-, full- and post-term dates.
- Pregnancy CalculatorFind out exactly how far along you are and what is coming next. Enter the first day of your last period — or a conception date, IVF transfer date, dated ultrasound or known due date — to see your gestational age today, the trimester boundaries, the term window and a dated week-by-week calendar with the checks and milestones clinicians watch for.
- Conception CalculatorWork backwards to the date conception most likely happened. Enter your due date, the first day of your last period, an ultrasound dating or — for a baby already born — the birth date, and the calculator returns the probable conception day, the range around it, the window in which intercourse could have led to it, and when implantation and a positive test would have followed.
- Ovulation CalculatorEstimate when you ovulate and the days you are most likely to conceive. Enter the first day of your last period and your average cycle length (and your luteal phase, if you know it) to see the ovulation date, the six-day fertile window and peak days for this cycle and the next six, with the earliest test date and the due date each cycle would give.
- Period CalculatorPredict when your next period will start — and the twelve after it. Enter the first day of your last period, your average cycle length and how long your period lasts to get a twelve-cycle calendar with period dates, fertile windows and ovulation days, plus where you are in your cycle today.
- Pregnancy Weight Gain CalculatorSee a general total pregnancy weight-gain range by pre-pregnancy BMI for one baby or twins, plus a week-by-week reference range and progress check for one baby.
Medical
- Body Surface Area CalculatorCalculate body surface area from height and weight. BSA is the size measure medicine uses for chemotherapy doses, cardiac index and kidney function, because it tracks metabolic rate better than weight alone. The calculator gives four standard formulas in square metres and square feet, with the ratio to the 1.73 m² reference adult.
- GFR CalculatorEstimate adult kidney filtration with the race-free 2021 CKD-EPI creatinine equation using age, sex coefficient and serum creatinine.
- BAC CalculatorExplore a simplified Widmark blood-alcohol estimate using ethanol grams, body mass, distribution coefficient and elapsed time.