Health & Fitness calculators

Serum anion gap with and without potassium, plus the albumin-corrected value, and an honest account of why the reference range differs between laboratories.

The five Apgar signs scored 0 to 2, using the AAP and ACOG descriptors, with what each total does and does not mean for a newborn.

The current Army body composition standard — waist-to-height ratio under 0.55 (AD 2026-13) — plus the rescinded AR 600-9 tape test, with the exact rules cited.

Estimate blood alcohol concentration with the Widmark formula from drinks, body weight, sex and hours elapsed, plus time until zero. Never a reason to drive.

Calculate your body mass index from height and weight, see your category, and find the weight range that counts as healthy for your height.

Child and teen BMI percentile for ages 2 to 19 from the official CDC LMS growth-chart parameters, with the CDC weight-status category and the curves for that age.

BMI Prime is your BMI divided by 25, so 1.00 sits exactly on the WHO overweight line. Shows the ratio, the BMI behind it and the WHO category.

Calculate your basal metabolic rate with Mifflin-St Jeor, Harris-Benedict or Katch-McArdle, compare all three, and see the math behind the number.

Estimate body fat percentage with the US Navy tape method, cross-check it against the BMI formula, and see your fat mass, lean mass and ACE category.

Calculate body surface area in m² by the Du Bois, Mosteller, Haycock and Gehan formulas at once, with the drug dose that BSA implies.

Which of the three classic body types your measurements resemble, from Heath-Carter ectomorphy, fat-free mass index and body fat — with the weak science labelled.

Band and cup from your bust and underbust measurements, with US, UK and EU equivalents, sister sizes, and what the fitting research says about the old +4 method.

Find how many calories a day to eat to maintain, lose or gain weight, with BMR and TDEE shown, Mifflin-St Jeor by default, and warnings if the target is too low.

Calories burned for 30+ activities using 2011 Compendium of Physical Activities MET values, scaled to your weight and duration, gross and net of resting.

Daily carbohydrate target in grams from your calories and diet split, with grams per meal, the IOM fibre target and the athlete g/kg bands for your training load.

CHA2DS2-VASc stroke risk in atrial fibrillation, with the annual event rate per score from a 73,538-patient untreated cohort and the sex-free CHA2DS2-VA variant.

Work backwards to the estimated conception date from a due date, a last period or a birth date, with the fertile window that produced it and an honest error range.

Albumin-corrected serum calcium by the standard 0.8 formula or Payne's original, in mg/dL and mmol/L, with the evidence on why it fails in critical illness.

Cockcroft-Gault creatinine clearance on actual, ideal and adjusted body weight, with why drug labels still use it rather than the CKD-EPI eGFR.

CURB-65 pneumonia severity scored from real observations, with the mortality band and the place of care NICE recommends considering at each score.

Work out the watts needed to hold a speed on any gradient, split into rolling resistance, air drag, gravity and drivetrain loss, from the Martin et al. model.

Daily fat target in grams from your calories, with the saturated-fat ceiling, the omega-6 and omega-3 essential fatty acid minimums, and the IOM 20–35% range.

Holliday-Segar routine maintenance fluid for children, in mL per day and per hour, with the daily ceilings and neonatal rates NICE sets alongside it.

Estimated GFR from serum creatinine using the race-free 2021 CKD-EPI equation, with the KDIGO stage — an estimate to discuss with a clinician, never a diagnosis.

Max heart rate by the Tanaka, 220−age or Gellish formula and five training zones in bpm — by percent of max or the Karvonen heart-rate-reserve method.

Predict a child's adult height from the parents' heights with the Tanner mid-parental formula, including the ±8.5 cm target range and what it cannot tell you.

Devine ideal body weight and adjusted body weight as used for drug dosing, with the 25%-over rule that FDA labelling uses to decide between them.

Compare your ideal body weight by the Devine, Robinson, Miller and Hamwi formulas and the healthy BMI range — with an honest note on where these numbers came from.

Estimate lean body mass with the Boer, James and Hume formulas, or directly from a measured body fat percentage, and see what share of your weight is lean tissue.

Turn daily calories into grams of protein, carbs and fat — balanced, low-carb, high-protein, keto or custom — with per-meal grams and a g/kg protein check.

Mean arterial pressure from a cuff reading, by the traditional one-third rule and the more accurate 0.412 multiplier, against the 65 mmHg perfusion target.

Estimate your one-rep max from any set using the Epley, Brzycki, Lombardi and O'Conner formulas, and get a percentage table for programming 1–12 rep sets.

Estimate ovulation and the six-day fertile window from your last period and cycle length, with the next three cycles mapped and an honest note on accuracy.

Find your running pace, finish time or distance from any two, in min/mile or min/km, with speed and projected times for 5K, 10K, half marathon and marathon.

Weight-based mg/kg dosing arithmetic with per-dose and daily ceilings. It supplies the arithmetic only — every number in it must come from approved labelling.

Predict your next several periods and fertile windows from your last period and cycle length, with the day of your cycle today and what counts as normal variation.

Due date from your last period, conception date, IVF transfer or a scan date, with how many weeks pregnant you are today, trimester and key milestone dates.

Recommended pregnancy weight gain by pre-pregnancy BMI and week, using the Institute of Medicine 2009 ranges, with twins handled and a week-by-week target table.

Daily protein in grams from body weight and goal, with cited g/kg ranges for sedentary, endurance, strength and fat-loss goals, plus a per-meal split.

Corrected QT interval by Bazett, Fridericia, Framingham and Hodges at once, with the reason Bazett over-corrects at fast heart rates and what to use instead.

Predict your time at any race distance from a recent result using Riegel's formula, with the pace you'd need and a full table of equivalent times.

Find the best time to go to bed or wake up by counting 90-minute sleep cycles plus the time it takes you to fall asleep — with alternatives at 4, 5 and 6 cycles.

Turn a step count into calories, distance and active minutes using Compendium MET values, with gross and net figures and an honest note on the 10,000-step target.

Convert a swim distance and time into pace per 100 m and per 100 yd, speed, length count, stroke count and SWOLF — with exact yard-metre conversion.

Estimate your total daily energy expenditure from BMR and activity level, see the number at every activity multiplier, and learn what each multiplier really means.

Estimate VO2 max from the Cooper 12-minute run, a 1.5-mile time trial, your resting heart rate or the Rockport walk test, with fitness norms by age and sex.

Check your waist-to-height ratio against the NICE and Ashwell cut-offs, see the waist size that keeps you under 0.5, and learn why it predicts risk better than BMI.

Estimate how much water to drink a day from body weight, exercise and climate, compared with the NASEM adequate intake — and an honest take on the '8 glasses' rule.

When you'll actually hit your goal weight at a given calorie deficit — the naive 3,500 kcal date plus a slower, realistic one that accounts for the plateau.

The two-level Wells score for deep vein thrombosis, scored exactly as NICE tabulates it, with the DVT likely and unlikely pathways each result leads to.