Health, fitness & clinical calculators
Every tool here runs a published equation, shows the working, and explains what the result actually means — including where the formula breaks down. No sign-up, no email wall, nothing stored: the math happens in your browser.
Educational estimates, not medical advice. Population equations cannot account for your individual physiology, medications, or history. Discuss any health decision with a licensed clinician, and seek immediate care for urgent symptoms.
Body composition
The four numbers that describe your body better than the scale does — and how they relate to each other.
Calculate body mass index from height and weight, see your WHO category, and get the weight range that maps to a healthy BMI.
Run itEstimate body fat percentage with the US Navy tape method from height, neck, waist, and hip measurements — plus lean mass and category.
Run itCalculate lean body mass and fat-free mass index from height, weight, and body fat — the numbers that actually track muscle.
Run itCompare ideal body weight across the Devine, Robinson, Miller, and Hamwi formulas plus the healthy BMI range for your height.
Run itCalculate waist-to-hip and waist-to-height ratios and see which WHO risk band you fall into — often a better risk signal than BMI.
Run itCalories & nutrition
Maintenance calories, deficit size, macro split, protein floor and hydration — the full intake stack in one place.
Calculate basal metabolic rate with the Mifflin-St Jeor equation — the calories your body burns at complete rest before any activity.
Run itFind your total daily energy expenditure — maintenance calories from BMR plus activity — with cut, maintain, and bulk targets.
Run itSee how big your calorie deficit needs to be for a target weekly fat loss rate — and whether that rate is sustainable for your body size.
Run itSplit your daily calories into protein, carbohydrate, and fat grams based on your goal, body weight, and preferred macro ratio.
Run itFind your daily protein target in grams based on body weight, training volume, age, and whether you are cutting, maintaining, or building.
Run itCalculate how much water to drink per day based on body weight, exercise duration, climate, and caffeine or alcohol intake.
Run itSee how many weeks it takes to reach a goal weight at your chosen deficit, with metabolic adaptation factored into the curve.
Run itTraining & cardio
Strength percentages, heart-rate zones, aerobic fitness and race-pace prediction from a single reference effort.
Estimate your one rep max from a set of reps using Epley, Brzycki, and Lombardi — plus a full training percentage chart.
Run itCalculate maximum heart rate and all five training zones using the Karvonen heart-rate-reserve method with your resting heart rate.
Run itEstimate VO₂ max from resting heart rate or a 1.5-mile run time and compare it against age and sex fitness norms.
Run itConvert pace to finish time across 5K, 10K, half marathon, and marathon — with equivalent race times and training pace ranges.
Run itConvert daily step count into calories burned and miles walked, adjusted for body weight, pace, and terrain.
Run itEstimate calories burned walking or hiking from duration, pace, incline, and body weight — including net versus gross burn.
Run itClinical reference
The equations clinicians use daily — kidney function, glucose conversion, ECG correction, lipid ratios and dosing surface area. Educational reference only.
Estimate glomerular filtration rate using the race-free CKD-EPI 2021 creatinine equation and see the corresponding CKD stage.
Run itEstimate creatinine clearance with the Cockcroft-Gault equation — still the standard for many renal medication dose adjustments.
Run itConvert A1C to estimated average glucose in mg/dL and mmol/L, in both directions, with diagnostic category bands.
Run itCalculate corrected QT interval across the Bazett, Fridericia, Framingham, and Hodges formulas and compare against prolongation thresholds.
Run itCalculate body surface area with the Mosteller, Du Bois, Haycock, and Boyd formulas — the basis for chemotherapy and cardiac index dosing.
Run itClassify a blood pressure reading into the ACC/AHA categories, with pulse pressure and mean arterial pressure calculated alongside.
Run itCalculate total-to-HDL ratio, LDL by the Friedewald equation, non-HDL cholesterol, and triglyceride-to-HDL ratio from a standard lipid panel.
Run itPregnancy, cycles & sleep
Dating, fertile windows and cycle-aligned bedtimes — the timing tools people search for most.
Estimate your due date and current gestational age from the first day of your last period, adjusted for cycle length.
Run itEstimate your ovulation day and six-day fertile window from cycle length and luteal phase length.
Run itWork out the bedtimes that let you wake at the end of a 90-minute sleep cycle, including time to fall asleep and your sleep debt.
Run itHow to read any health number on this site
Trend beats snapshot
A single BMI, body-fat reading, or lab value carries measurement noise. Four readings across a month tell you the direction, which is the part you can actually act on.
Every equation has a domain
Friedewald LDL breaks above 400 mg/dL triglycerides. Bazett QTc distorts away from 60 bpm. BMI misreads muscular athletes. Each page names the limitation rather than hiding it.
Estimates are hypotheses
Calculated TDEE is a starting point; two weeks of tracked intake and weight tells you the real number. Adjust from measured reality, not from the formula.
Clinical values need clinical context
eGFR, QTc, and lipid ratios mean different things depending on medications, hydration, and history. Bring the number to a clinician; do not act on it alone.
Frequently asked questions
Are these health calculators accurate?
They use the same published equations clinicians and exercise physiologists use — Mifflin-St Jeor for metabolism, CKD-EPI 2021 for kidney function, ACSM for walking energy cost, Friedewald for LDL. Population equations carry real error bars for any individual, which is why each tool states its typical accuracy and none of them replace a measurement or a clinician.
Is any of my data stored?
No. Every result is computed in your browser. Nothing you enter is transmitted, saved, or attached to you, and there is no sign-up or email wall.
Which calculator should I start with?
For body composition and weight goals, start with TDEE — almost every other nutrition number depends on it. For general health screening, waist-to-height ratio and blood pressure category tell you more in thirty seconds than BMI alone.
Can these tools diagnose a medical condition?
No. Clinical calculators here reproduce reference equations for education. Diagnosis requires laboratory confirmation, clinical context, and a qualified clinician interpreting the full picture.
Why do different sites give me different numbers?
Different base equations and different activity tiers. A 200 kcal spread between TDEE calculators is normal, as is a few percent between BSA formulas. Pick one and track the trend rather than switching tools.
How often should I recalculate?
Recalculate TDEE and BMR every 10–15 lb of weight change, body composition every 2–4 weeks, and clinical values whenever new labs come back.