Free BMR Calculator (UK Units Supported)
Use this calculator to estimate your Basal Metabolic Rate (BMR) and your likely daily maintenance calories. Choose metric or imperial units (including stone and pounds), enter your details, and click calculate.
What is Basal Metabolic Rate (BMR)?
Your Basal Metabolic Rate is the number of calories your body needs every day to keep you alive at complete rest. Think breathing, circulation, cell repair, and temperature regulation. Even if you stayed in bed all day, your body would still burn energy.
For most people in the UK, BMR usually accounts for the largest share of total daily calorie burn. On top of BMR, you also burn calories through movement, exercise, digestion, and everyday tasks like walking to the station, carrying shopping, or climbing stairs.
How to use this UK BMR calculator
- Select Metric if you know your weight in kilograms and height in centimetres.
- Select Imperial if you prefer stone/pounds and feet/inches.
- Enter your age and sex.
- Choose your activity level to estimate your maintenance calories (TDEE).
- Click calculate and use the output as a starting point, then adjust based on real progress.
BMR vs TDEE: what’s the difference?
BMR
BMR is your baseline energy use at rest. It is not the number of calories you should eat if you are living a normal life.
TDEE (Total Daily Energy Expenditure)
TDEE is BMR multiplied by your activity level. This gives a more realistic estimate of calories needed to maintain your weight.
- Eat around TDEE to maintain weight.
- Eat below TDEE to lose fat.
- Eat above TDEE to gain weight.
Formulas used in this calculator
1) Mifflin-St Jeor (recommended)
Widely used in modern nutrition coaching because it tends to be reliable for many adults.
- Male:
10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 - Female:
10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
2) Revised Harris-Benedict
An updated version of a classic formula. Some users prefer to compare both equations and track which one aligns best with real results.
- Male:
88.362 + 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age - Female:
447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age
How accurate is a BMR calculator?
BMR calculators are useful, but they are still estimates. Two people with identical age, height, and weight can have different metabolic rates due to genetics, muscle mass, hormones, medications, sleep quality, stress, and medical conditions.
A practical approach is:
- Use the calculator result as your starting point.
- Track body weight and waist measurements for 2-4 weeks.
- Adjust intake by 100-250 kcal if progress is too slow or too fast.
Setting calories for your goal
Fat loss
Start around 300-500 kcal below maintenance. Aim for steady progress and preserve muscle by keeping protein high and resistance training regularly.
Maintenance
Eat around your estimated TDEE. If your weight drifts up or down over several weeks, adjust your intake slightly.
Muscle gain
Add roughly 150-300 kcal above maintenance and combine with progressive strength training.
Common UK questions
Can I use stone instead of kilograms?
Yes. This calculator supports stone and pounds directly. Internally, values are converted to kilograms for the equation.
Is BMR the same as resting metabolic rate (RMR)?
Not exactly. They’re very close, but RMR is measured under less strict conditions. In everyday use, most people treat them as near-equivalent estimates.
Why does my calorie target seem higher than expected?
People often underestimate maintenance needs, especially if they are active, taller, or have higher lean mass. Track outcomes for a few weeks before making big changes.
Final thoughts
A solid BMR estimate can remove guesswork from nutrition planning. Use your result to set a clear calorie target, track consistently, and make small data-driven adjustments over time. If you have thyroid conditions, metabolic disorders, or other health concerns, check your plan with a GP or registered dietitian.