Free calculator
BMI & maintenance calorie calculator
Your BMI from your height and weight. Then, if you want it, an estimate of the calories your body uses in a day.
Your BMI
BMI compares your weight with your height. It is a starting guide, not an assessment of your overall health.
BMI categories are for adults aged 18 and over. More about BMI
Estimated maintenance calories
kcal a day
Resting estimate (BMR): kcal a day
An estimate of what your body uses in a day, from the Mifflin–St Jeor equation and your activity level. It is not a target or a prescription.
About BMI
What your result means
BMI is your weight in kilograms divided by the square of your height in metres. The calculator rounds it to one decimal place and reads that figure against the standard adult ranges.
| BMI | Range |
|---|---|
| Below 18.5 | Underweight range |
| 18.5 to below 25 | Healthy BMI range |
| 25 to below 30 | Overweight range |
| 30 or above | Obesity range |
Its limits
What BMI cannot tell you
It is an adult screening estimate
BMI is a quick screening measure for adults aged 18 and over. It is not a diagnosis. Children and teenagers are still growing, so their BMI is read against growth charts for their age and sex instead.
It does not tell muscle from fat
The same height and weight give the same BMI whether that weight is mostly muscle or mostly fat. Very muscular people can read high, and people who have lost muscle can read lower than their body fat suggests.
It does not apply in pregnancy
Weight changes during pregnancy for good reasons, so the adult BMI ranges do not apply. Your doctor or midwife is the right person to talk to about weight while you are pregnant.
Maintenance calories are estimates
The daily estimate comes from the Mifflin–St Jeor equation and an activity multiplier. Real needs vary from person to person, so treat it as a starting estimate, not an exact figure.
A programme is not built from BMI alone
A Slim Diet programme is never generated from your BMI. Your plan is shaped by what you tell us about your goals, food preferences, routine and training setup.
Your measurements stay on this page
Your height, weight and answers are worked out in your browser. We do not send them to our server, save them, or add them to the page address.
Want a plan that fits your life?
Explore the personalised nutrition and training programme. You do not need to calculate anything first.