Health Calculators

Everyday body and date maths

These tools cover the personal numbers that come up in ordinary life — body measurements, calorie estimates, ages, and running paces. Each one shows the formula it uses and explains what the result does and doesn't tell you, so you can judge it rather than just accept it.

The BMI calculator andideal weight calculator place height and weight against standard population ranges, while thecalorie and BMR calculator estimates daily energy needs. For dates, the age calculator anddate difference calculator handle leap years and varying month lengths exactly, and therunning pace calculator converts a distance and time into pace and speed.

These are general-information estimates, not medical advice.Formulas like BMI and BMR are based on population averages and can't account for individual body composition, health conditions, or circumstances. Speak to a doctor or qualified professional before making decisions about your health.

Population formulas describe populations

Every formula in this category was derived by fitting a curve to measurements of a large group of people. That makes them useful for orientation and unreliable for individuals, and the distinction is not pedantic. BMI was devised in the nineteenth century as a population-level statistic and cannot distinguish muscle from fat, which is why it misclassifies athletes routinely. Basal metabolic rate equations such as Mifflin-St Jeor carry a meaningful spread even among people who match the study group closely.

So treat a result here as a reference point, not a verdict. If a number surprises you, the useful response is to ask a professional who can take your actual circumstances into account, rather than to change anything on the strength of a web page.

Which formula, and why it is named

Where several competing equations exist, the page names the one it uses and usually offers the alternatives — the ideal weight calculator reports Devine, Robinson and Miller side by side precisely because they disagree, and seeing the spread is more informative than any single figure. Naming the formula also lets you check it against whatever source your clinician or coach is working from.

The tools that are simply arithmetic

Not everything here is a population estimate. The age and date difference calculators are exact calendar arithmetic, including leap years. The running pace calculator is a straightforward conversion between distance, time and speed. TheIV drip rate calculator converts between volume, time and drops using the giving set's drop factor — it makes no clinical judgement and is not a substitute for a prescription or local protocol.

Nothing in this category is medical advice. These are general-information tools, and decisions about health, medication or treatment belong with a qualified professional.