BMR Calculator
Use our BMR calculator to estimate your Basal Metabolic Rate, which is the number of calories your body needs each day at rest. This tool allows you to choose between metric or imperial measurements and select a calculation method such as Mifflin–St Jeor or the revised Harris–Benedict formula.
Enter your age, gender, height and weight below to see your estimated BMR and an approximate daily calorie intake based on different activity levels.
Enter your age, gender, height and weight below to see your estimated BMR and an approximate daily calorie intake based on different activity levels.
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Disclaimer: This calculator provides general estimates only and is not a substitute for medical or nutritional advice. Last checked/updated February 2026.
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How the BMR Calculator Works
This calculator estimates your Basal Metabolic Rate using standard metabolic formulas. BMR is the amount of energy your body uses to maintain basic functions at rest, such as breathing and circulation.
The calculator uses:
The calculator uses:
It then calculates your estimated BMR and applies activity multipliers to show an estimated daily calorie intake for different activity levels.
Mifflin–St Jeor vs Revised Harris–Benedict
Both formulas are widely used to estimate BMR, but they can produce slightly different results.
This calculator allows you to choose the method you prefer.
Daily Calorie Intake by Activity Level
After calculating your BMR, the calculator estimates your daily calorie needs based on activity level:
These figures provide an estimate of maintenance calories, meaning the approximate intake needed to maintain your current weight.
Common BMR Scenarios
Example 1: The Impact of Activity Levels
Consider a 35-year-old female who is 165cm tall and weighs 65kg.
– Her resting BMR (using the Mifflin-St Jeor formula) is approximately 1,365 calories. This is the energy her body needs just to function if she stayed in bed all day.
– If she works a desk job (Sedentary), her maintenance calories rise to around 1,638 per day.
– If she exercises 4 days a week (Moderately Active), her maintenance calories jump to 2,115 per day.
Example 2: How Age Affects BMR
Metabolism naturally slows down as we age due to muscle loss and changes in cellular function.
– A 25-year-old male who is 180cm tall and weighs 80kg has an estimated BMR of 1,822 calories.
– Using the exact same height and weight, a 65-year-old male’s BMR drops to roughly 1,622 calories.
Takeaway: This is why diet and portion sizes often need to be adjusted as we get older, even if our physical activity remains the same.
Consider a 35-year-old female who is 165cm tall and weighs 65kg.
– Her resting BMR (using the Mifflin-St Jeor formula) is approximately 1,365 calories. This is the energy her body needs just to function if she stayed in bed all day.
– If she works a desk job (Sedentary), her maintenance calories rise to around 1,638 per day.
– If she exercises 4 days a week (Moderately Active), her maintenance calories jump to 2,115 per day.
Example 2: How Age Affects BMR
Metabolism naturally slows down as we age due to muscle loss and changes in cellular function.
– A 25-year-old male who is 180cm tall and weighs 80kg has an estimated BMR of 1,822 calories.
– Using the exact same height and weight, a 65-year-old male’s BMR drops to roughly 1,622 calories.
Takeaway: This is why diet and portion sizes often need to be adjusted as we get older, even if our physical activity remains the same.
When Should You Use a BMR Calculator?
This calculator is useful when you want to:
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About This BMR Calculator
This BMR calculator uses widely recognised formulas to estimate basal metabolic rate and daily calorie requirements. It is designed to provide clear, accessible results using simple inputs.
Calorie needs vary significantly based on health, lifestyle and individual metabolism, so results should be treated as general guidance only.
If you are making significant changes to your diet or exercise routine, always consult a registered dietitian, GP, or refer to official NHS guidelines on healthy eating.
Calorie needs vary significantly based on health, lifestyle and individual metabolism, so results should be treated as general guidance only.
If you are making significant changes to your diet or exercise routine, always consult a registered dietitian, GP, or refer to official NHS guidelines on healthy eating.
Frequently Asked Questions
What is BMR?
BMR stands for Basal Metabolic Rate. It is the number of calories your body needs each day at rest.
Which formula should I choose?
Both methods are widely used. Mifflin–St Jeor is commonly used in modern settings, while revised Harris–Benedict is also widely referenced.
Does this calculator show TDEE?
It provides estimated calorie needs for different activity levels, which is similar to total daily energy expenditure.
What is the difference between BMR and TDEE?
Basal Metabolic Rate (BMR) is the absolute minimum number of calories your body needs to survive at rest. Total Daily Energy Expenditure (TDEE) is your BMR plus the calories you burn through daily movement and exercise. Your BMR stays relatively static, but your TDEE changes depending on how active you are on any given day.
Can I use imperial measurements?
Yes. You can enter your height and weight using either metric or imperial units.
Disclaimer
This calculator provides general estimates only and should not be used as medical or dietary advice.