Health and fitness calculators

Body composition, energy expenditure and training zones. Every one of these is an estimate, and each page says how big its margin of error is, because a health number without its uncertainty is worse than no number at all.

• BMI Calculator At 70 kg and 175 cm your BMI is 22.9, inside the healthy range the WHO puts at 18.5 to 25
• Ideal Weight Calculator Six formulas, six different answers: for a 175 cm man they run from about 68 to 75 kg
• BMR Calculator A 30-year-old man of 70 kg and 175 cm burns about 1,649 kcal a day doing absolutely nothing
• TDEE Calculator Take your resting burn and multiply it by how much you move: a moderately active 30-year-old man of 70 kg lands around 2,556 kcal a day
• Body Fat Calculator Measure your neck, waist and hip and the US Navy formula estimates your body fat: about 17 % for a 175 cm man with an 85 cm waist
• Lean Body Mass Calculator Of 70 kg at 175 cm, roughly 58 kg is lean mass and 12 kg is fat
• Calorie Deficit Calculator Losing half a kilo a week needs a deficit of about 550 kcal a day
• Macro Calculator On 2,556 kcal a day a 70 kg adult gets about 112 g of protein, 70 g of fat and 369 g of carbohydrate
• Waist to Hip Ratio Calculator An 85 cm waist and 98 cm hip give a ratio of 0.87, below the 0.90 threshold for men
• Body Surface Area Calculator At 70 kg and 175 cm your body surface area is about 1.84 m² by Mosteller
• Water Intake Calculator At 70 kg with 30 minutes of exercise, about 2.8 litres a day: 2,450 ml for your weight plus 350 for the training
• Max Heart Rate Calculator At 30 your maximum heart rate is about 187 bpm by the Tanaka formula, not the 190 the old 220-minus-age rule gives
• Swim Pace Calculator Swimming pace is measured per 100 metres, not per kilometre
• Apgar Score Calculator The Apgar score sums up a newborn’s condition in the first minutes of life as a number from 0 to 10
• Daily Protein Calculator How much protein you need a day given your weight and what you do, in grams and in calories
• Healthy Weight for Height Calculator The weight range that matches a healthy BMI for your height, and where yours sits inside it
• VO2 Max Calculator Your estimated maximum oxygen uptake from a field test: the twelve-minute Cooper run, the mile and a half, your resting pulse, or the Rockport one-mile walk
• Steps to Kilometres Calculator The steps your phone counts, turned into kilometres and calories
• Blood Glucose Converter Converts blood glucose between milligrams per decilitre and millimoles per litre, the two units the same thing is measured in depending on the country, and gives the matching A1c
• IV Drip Rate Calculator The drip rate of an infusion: how many drops per minute to set for a given volume over a given time, using the drop factor of whichever set you have
• Blood Alcohol Calculator An estimate of blood alcohol using the Widmark equation, from what you drank, your weight and the time since
• Alcohol Elimination Time Calculator How long until alcohol leaves your blood, and how long until it drops below a given limit
• Caffeine Half-Life Calculator How much caffeine is still in your body after a few hours
• Cholesterol Ratio Calculator The atherogenic ratios from your blood test, with LDL calculated by Friedewald when it is not measured
• Mean Arterial Pressure Calculator Mean arterial pressure and pulse pressure from the two numbers on your monitor
• Child Adult Height Predictor A child's estimated adult height from their parents', using the mid-parental method
• Rule of Nines Burn Calculator Total body surface area burned by the rule of nines, and fluid resuscitation by the Parkland formula
• Serum Osmolality Calculator Calculated serum osmolality from sodium, glucose and blood urea nitrogen, plus the osmolal gap if you also have the laboratory's measured value
• Calories Burned Calculator Half an hour of running burns about 360 kcal if you weigh 70 kilos, and the same half hour of walking burns 129
• FTP Calculator If you held 280 watts for twenty minutes, your FTP is 266
• Drug Dosage by Weight A child of 18 kilos on 15 mg/kg a day split into four doses needs 67.5 mg each time, which with a syrup of 100 mg per 5 ml is 3.4 ml
• Pediatric Dose Calculator The three classic rules give 143, 167 and 240 milligrams for the same child and the same adult dose
• Quit Smoking Calculator A pack a day at 5.50 is 165 a month and more than 2,000 a year
• Sleep Cycle Calculator To wake at seven, go to bed at 23:15 or at 21:45, not somewhere in between: those are the times that close a complete cycle
• GFR Calculator A creatinine of 1.1 mg/dl in a 55-year-old man is about 79 ml/min/1.73 m²
• Oral Rehydration Calculator A 12-kilo child at 5% dehydration has lost 600 ml, and over four hours needs about 783 counting maintenance

Not medical advice. These calculators are for information. For anything that affects treatment, diet in a medical context or training under supervision, talk to a qualified professional.