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Tools Free calculators that show their working

Health & Fitness Calculators

Calculators for calories, macros, body fat, pregnancy dates and cycle tracking, built on the formulas used by dietitians, clinicians and public health bodies such as the NHS and CDC. Each page names its formula, cites its sources and explains the limits of an estimate.

These tools are for information and planning. They do not replace advice from a doctor, midwife or registered dietitian.

Body Fat Calculator

A body fat calculator estimates what percentage of your weight is fat. Using the US Navy tape method,…

Calorie Calculator

A calorie calculator estimates how many calories you burn in a day and how many to eat to…

Due Date Calculator

A due date calculator estimates when your baby is due by adding 280 days (40 weeks) to the…

Macro Calculator

A macro calculator turns a calorie target into grams of protein, carbohydrate and fat. A moderately active 35-year-old…

Ovulation Calculator

An ovulation calculator predicts your fertile days from your cycle. Ovulation usually happens about 14 days before your…