Health & Fitness Calculators

What these numbers can and cannot tell you

BMI is a population-level screening tool, not an individual diagnosis. It uses only height and weight, so it cannot distinguish muscle from fat. A well-trained athlete frequently registers as overweight or obese by BMI while carrying very low body fat. Treat it as one rough input among several, not a verdict.

BMR estimates the energy your body uses at complete rest. Multiplying it by an activity factor gives approximate daily calorie needs. The formulas here (Mifflin-St Jeor and Harris-Benedict) are the standard clinical equations, but individual metabolic rates vary meaningfully around the estimate, so use the output as a starting point and adjust based on what actually happens over several weeks.

Pregnancy due date calculation uses Naegele's rule, counting 280 days from the first day of the last menstrual period. It assumes a regular 28-day cycle, and only a small minority of births occur precisely on the estimated date — most arrive within a two-week window either side. An ultrasound dating scan is considerably more accurate.

These tools are for general information only. They are not a medical device and do not replace advice from a qualified healthcare professional, particularly for any decision involving pregnancy, a medical condition, or a significant change in diet or exercise.