How to Calculate BMR: A Step-by-Step Guide

Updated 5 Oct 2026 in Health & Fitness

Estimates calories your body burns at rest.

Health numbers are most useful when you track them consistently. A quick calculation turns everyday measurements into something you can act on, whether that is planning meals, training for a run or preparing for a clinic visit.

What you need

• Sex
• Weight (kg)
• Height (cm)
• Age

Step by step

1. Enter the sex.
2. Enter the weight (kg).
3. Enter the height (cm).
4. Enter the age.
5. The results update as you type, or press Calculate.
6. Read the bmr (mifflin-st jeor) first, then the supporting figures below it.

The formula

BMR = 10W + 6.25H − 5A + 5 (men) or − 161 (women).

Worked example

For example, with these inputs:

• Sex: Male
• Weight (kg): 65
• Height (cm): 168
• Age: 35

the calculator returns:

• BMR (Mifflin-St Jeor): 1,530 kcal/day

A second example

Now change the inputs to:

• Sex: Male
• Weight (kg): 81.25
• Height (cm): 168
• Age: 35

the calculator returns:

• BMR (Mifflin-St Jeor): 1,693 kcal/day

Practical tips

• Singapore's heat and humidity raise fluid needs, especially when exercising outdoors.
• Formulas give estimates for the average person; your doctor can account for your history and body composition.
• Healthy 365 and wearables give useful data, but treat their calorie figures as approximate.
• Asian BMI cut-offs are lower than WHO's, so a 'normal' international BMI can still mean moderate risk.

Background

Energy needs depend on age, sex, size and activity. Formulas such as Mifflin-St Jeor estimate resting needs, and an activity multiplier turns that into daily needs. Real requirements vary by a few hundred calories, so adjust based on how your weight changes over several weeks.

Any health calculator gives a general estimate. If a result worries you, or you are pregnant, managing a chronic condition or planning a big change in diet or exercise, speak to a doctor, polyclinic or dietitian.

Simple measurements such as weight, height and waist circumference are widely used to screen for health risks because they are cheap and easy to repeat. They are not diagnoses, but tracked over time they show whether lifestyle changes are working.

Related calculations

• Pregnancy Due Date Calculator: Estimates your due date using Naegele's rule.
• Ovulation Calculator: Estimates ovulation and the fertile window.
• Heart Rate Zone Calculator: Shows heart-rate training zones from your age.
• Waist-to-Height Ratio Calculator: A ratio above 0.5 suggests increased health risk.

Want to skip the arithmetic? The free BMR Calculator does all of this instantly and updates as you type.

Run your own numbers: BMR Calculator