Health & Fitness Calculators
Track body composition, calorie needs, and the numbers behind your goals. All 97 are free and run in your browser. Each one shows the formula behind the result.
BMI Calculator
Body mass index with category and healthy weight range.
OpenCalorie & BMR Calculator
Daily calorie needs for losing, holding, or gaining weight.
OpenBody Fat Calculator
Body fat percentage from tape measurements.
OpenIdeal Weight Calculator
Target weight from four clinical formulas plus BMI range.
OpenPregnancy Due Date Calculator
Due date, current week, and trimester milestones.
OpenWater Intake Calculator
Daily hydration target adjusted for exercise and climate.
OpenLean Body Mass Calculator
Everything you weigh that is not fat.
OpenFFMI Calculator
Fat-free mass index, muscularity adjusted for height.
OpenWaist-to-Hip Ratio Calculator
Where you carry fat, and what the WHO says about it.
OpenWaist-to-Height Ratio Calculator
Keep your waist under half your height.
OpenBody Surface Area Calculator
BSA by Du Bois, Mosteller, Haycock and Boyd.
OpenBMI Prime Calculator
Your BMI as a simple ratio to the upper healthy limit.
OpenPonderal Index Calculator
A leanness index that handles very tall and short people better.
OpenAdjusted Body Weight Calculator
Ideal, actual and adjusted weight for dosing.
OpenBody Adiposity Index Calculator
Body fat estimated from hip size and height, no weight needed.
OpenSkinfold Body Fat Calculator
Jackson-Pollock 3-site caliper method.
OpenBMR Calculator
Basal metabolic rate by three formulas, side by side.
OpenTDEE Calculator
Total daily energy expenditure and what each part contributes.
OpenMacro Calculator
Protein, fat and carbs in grams for your goal.
OpenProtein Intake Calculator
Daily protein target for your body weight and goal.
OpenCalorie Deficit Calculator
How big a deficit gives the rate of loss you want.
OpenGoal Weight Date Calculator
When you will reach your target weight at your current rate.
OpenCalories Burned Calculator
Energy cost of an activity from its MET value.
OpenCarb Calculator
Daily carbohydrate target, including a low-carb option.
OpenFiber Intake Calculator
Daily fibre target and how far typical diets fall short.
OpenSugar Intake Calculator
Your added-sugar limit in grams and teaspoons.
OpenMax Heart Rate Calculator
Four formulas, because 220 minus age is the worst of them.
OpenTarget Heart Rate Calculator
Karvonen zones using your resting heart rate.
OpenHeart Rate Zone Calculator
All five training zones, with what each is for.
OpenVO2 Max Calculator
Aerobic capacity estimated from resting heart rate or a race time.
OpenOne Rep Max Calculator
Estimated 1RM plus a full percentage table.
OpenRunning Pace Calculator
Pace, speed and splits for any distance and time.
OpenRace Time Predictor
Predict a race time from a result at another distance.
OpenSteps to Calories Calculator
What your daily step count actually burns.
OpenWilks Score Calculator
Compare powerlifting totals across body weights.
OpenPower-to-Weight Ratio Calculator
Watts per kilogram, and what it means on a climb.
OpenMean Arterial Pressure Calculator
MAP from systolic and diastolic, with perfusion thresholds.
OpenBlood Pressure Category Calculator
Where a reading falls on the ACC/AHA scale.
OpenCholesterol Ratio Calculator
Total:HDL, LDL:HDL and triglyceride ratios.
OpenCreatinine Clearance Calculator
Cockcroft-Gault, the standard for renal drug dosing.
OpeneGFR Calculator
CKD-EPI 2021, without the race coefficient.
OpenCorrected Calcium Calculator
Adjusting total calcium for a low albumin.
OpenAnion Gap Calculator
Anion gap with albumin correction and delta ratio.
OpenQTc Calculator
Bazett, Fridericia, Framingham and Hodges corrections.
OpenAPGAR Score Calculator
Newborn assessment at one and five minutes.
OpenPediatric Fluid Calculator
Holliday-Segar maintenance fluids for children.
OpenOvulation Calculator
Fertile window and likely ovulation day.
OpenPeriod Calculator
Next several periods from your cycle length.
OpenConception Date Calculator
Estimated conception date from a due date or last period.
OpenPregnancy Weight Gain Calculator
Recommended gain by pre-pregnancy BMI and week.
OpenSleep Calculator
Bedtimes and wake times aligned to sleep cycles.
OpenSleep Debt Calculator
How much sleep you have accumulated a deficit of.
OpenChild Height Predictor
Adult height from parents, by the mid-parental method.
OpenSmoking Cost Calculator
What smoking costs in money and in time.
OpenAlcohol Units Calculator
Units and standard drinks against weekly guidelines.
OpenSweat Rate Calculator
Fluid lost per hour, from weight before and after.
OpenVDOT Running Calculator
One race result, every training pace.
OpenRace Time Predictor
Doubling the distance costs more than double the time.
OpenSwim Pace & CSS Calculator
Pace per 100, plus critical swim speed from two trials.
OpenCycling Power Calculator
Where your watts actually go — mostly into the air.
OpenWatts Per Kilogram Calculator
Predicts climbing. Predicts almost nothing on the flat.
OpenSleep Cycle Calculator
Wake at the end of a cycle, not the middle of one.
OpenJet Lag Calculator
Eastward is harder, and there is a reason.
OpenMacro Split Calculator
Percentages of energy, not of weight.
OpenGlycemic Load Calculator
Watermelon has a high index and a low load.
OpenBlood Alcohol Calculator
Predicts an average. Never predicts you.
OpenCaffeine Half-Life Calculator
Half-life ranges from two hours to twelve.
OpenWaist to Hip Ratio Calculator
Where fat sits, not how much there is.
OpenMeal Prep Calculator
Four days chilled. Beyond that, freeze it.
OpenPlate Loading Calculator
Tells you when a weight cannot be loaded.
OpenTraining Volume Calculator
Tonnage is the easy number and the wrong one.
OpenRest Between Sets Calculator
Short rests are not more efficient for strength.
OpenGrip Strength Calculator
Outperforms blood pressure as a mortality predictor.
OpenFlexibility Score Calculator
Long arms flatter the score. Proportions confound it.
OpenStep Count Calculator
The 10,000 target came from a 1960s advert.
OpenJet Lag Recovery Calculator
Eastward is harder, and the reason is physiological.
OpenHiking Time Calculator
Naismith is a minimum, not an estimate.
OpenElevation Gain Calculator
A loop has zero net change and all the climbing.
OpenBackpack Weight Calculator
Base weight is the only part you carry every day.
OpenRunning Pace Calculator
Pace is a reciprocal. It cannot be averaged like speed.
OpenRace Split Calculator
Nearly every record has been set on a negative split.
OpenMarathon Time Predictor
Doubling a half marathon time is not the answer.
OpenRowing Split Calculator
Halving the split takes eight times the power.
OpenTriathlon Time Calculator
Transitions are free time almost nobody trains.
OpenSwimming Pace Calculator
Stroke count is the metric that shows real improvement.
OpenCamping Water Calculator
A litre weighs a kilogram, which is the whole problem.
OpenPet Medication Dose Calculator
Arithmetic on a prescription, not a prescription.
OpenFlight Carbon Footprint Calculator
One long return flight is most of an annual budget.
OpenSourdough Starter Calculator
Your starter smuggles flour and water into the dough.
OpenBaker's Percentage Calculator
Flour is always 100%. Everything else is a ratio to it.
OpenPizza Dough Calculator
Dough scales with area. Double the diameter, quadruple the dough.
OpenYeast Conversion Calculator
Fresh to instant divides by three. Not by two.
OpenBrine Calculator
Equilibrium brining cannot over-salt. Traditional very much can.
OpenSous Vide Calculator
Thickness sets the time. Weight is irrelevant.
OpenMeat Roasting Time Calculator
Pull it below the target. Carryover does the rest.
OpenCoffee Ratio Calculator
Weak and under-extracted need opposite fixes.
OpenPan Size Conversion Calculator
Depth sets the bake time, not area.
OpenAbout health & fitness calculations
Health numbers are population estimates applied to an individual, and that gap is where most of the confusion lives. A formula derived from thousands of people describes the average of those people; it does not know your muscle mass, your medical history or your genetics. That does not make the numbers useless; it makes them a starting point rather than a verdict.
The calculators here name the formula they use and state where it breaks down. BMI cannot distinguish muscle from fat. The US Navy body fat method carries a standard error of three to four percentage points. Due dates are accurate to within two weeks for about 90% of pregnancies. Knowing the error bar is part of using the number properly.
Several of the tools in this category: eGFR, QTc, anion gap, corrected calcium, APGAR, paediatric fluids, implement equations written for clinicians. They inform a clinical decision; they do not make one.
Which one do you need?
I want to know if my weight is healthy
BMI is the standard screening number and the fastest place to start, but waist-to-height ratio predicts metabolic risk better and needs only a tape measure, keep your waist under half your height. If you train seriously, body fat percentage or FFMI will describe you far more accurately than either.
I want to know how much to eat
Work out BMR first, then TDEE, which multiplies it by an activity factor to give your maintenance calories. From there the calorie deficit calculator sets a target for a chosen rate of loss, and the macro calculator splits it into protein, fat and carbohydrate.
I want to train more effectively
Max heart rate sets the scale everything else is measured against, use the Tanaka formula rather than 220 minus age, which was never derived from a proper study. From there, heart rate zones and target heart rate use your resting pulse to personalise the ranges.
I am tracking a pregnancy
The due date calculator works from your last period or a conception date and shows the current week alongside the milestone timeline. Ovulation and period calculators cover the cycle itself, and pregnancy weight gain uses the Institute of Medicine ranges by pre-pregnancy BMI.