Free Health & Fitness
Everyday measurements like BMI and calorie needs. These are for information only, nothing here is medical advice.
Tools in this category
1 toolNumbers with their limits attached
Every figure on these pages comes from a formula somebody published, fitted to a population, with a known amount of error. None of them can see you. BMI cannot tell muscle from fat. A calorie equation does not know your thyroid or how much you fidget. A tape measure estimate of body fat is only as good as where you put the tape.
That is not a reason to avoid the numbers. It is a reason to publish what they cannot do next to what they can, which is what these pages try to do rather than printing a figure and moving on.
Where the number sits, not just what it is
A BMI of 26 means nothing on its own. What people want to know is whether that is a little over or a lot, and how far away the healthy range is. So the number gets placed on a banded scale with the boundaries drawn, and the weight range for your height is worked out in the units you were already using.
The same idea drives the calorie tool. Instead of asking you to pick an activity level from a dropdown you cannot verify and printing one number, it charts all five side by side, because the gap between a desk job and moderate activity is larger than most people's intended deficit.
The cut points are conventions
18.5, 25 and 30 are round numbers standing in for a smooth curve. Nothing changes about a body when it crosses one, and somebody at 24.9 and somebody at 25.1 are in the same situation and in different categories. The scales here are drawn to make that obvious rather than to hide it behind a colour change.
Several health bodies also use lower BMI thresholds for people of South Asian, Chinese and some other backgrounds, because risk appears at a lower figure. The numbers shown are the general WHO ones, and the pages say so.
Both unit systems, everywhere
Half the people who look up a BMI think in stones and feet, and the other half in kilograms and centimetres. A calculator that accepts only one loses the rest at the very first field, which is a strange way to build something meant to be quick. Every tool here that takes a measurement takes both, converted through exact factors so the two agree rather than drifting apart in the third decimal place.
Feet and inches are separate fields rather than a decimal, because nobody thinks of their height as 5.75 feet. Small thing, and it is the difference between a form you can fill in without stopping to convert and one you abandon.
What none of these will do
They will not diagnose anything, build you a diet, or set you a target. They do not adjust for medical conditions or medication, both of which can move these numbers substantially. And they stop short of very low calorie figures, because that is a clinical decision rather than a calculator's.
Questions people ask
Is any of this medical advice?
No, and every page here says so. These are published formulas that describe populations, and they cannot see your health, your history or your build. They are useful as a prompt and as a way to track change over time. Anything that actually matters is a conversation with a doctor or a dietitian.
Which formulas do you use?
Named, published ones, and each page says which. BMI is the Quetelet index with the WHO cut points. Calories use Mifflin St Jeor, which replaced Harris Benedict in most clinical practice. Body fat uses the US Navy circumference method. Ideal weight shows Hamwi, Devine, Robinson and Miller together, because they disagree and hiding that would be dishonest.
Why show four ideal weight formulas instead of one?
Because there are at least four in common use and they differ by several kilograms at the same height. Most calculators pick one silently. Showing them scattered against the healthy BMI range gives you the true shape of the answer, which is a range rather than a target.
Do the numbers differ for men and women?
For some tools, substantially. Body fat categories differ because essential fat differs by roughly a factor of three, and applying a male scale to a woman makes a healthy figure look alarming. BMI uses the same adult cut points for both. Each page says which case it is in.
Do these work for children?
No. Children are assessed on age and sex specific percentile charts, because normal body composition changes a great deal through growth. Everything here is for adults.
Metric or imperial?
Both, everywhere it applies, converted through exact factors so the two agree rather than drifting apart. A calculator that only accepts centimetres loses half its audience at the first field.