Online BMR Calculator
Calculate your Basal Metabolic Rate with the Mifflin St Jeor, Harris-Benedict, or Katch-McArdle formula, plus daily calorie needs by activity — free.
BASAL METABOLIC RATE (calories per day)
| ACTIVITY LEVEL | TIME | FREQUENCY | CALORIES |
|---|---|---|---|
| No Activity | 0 minutes | Little or no exercise | |
| Low Activity | 15-30 minutes | 1-3 times per week | |
| Light Activity | 15-30 minutes | 4-5 times per week | |
| Medium Activity | 15-30 minutes | 3-4 times per week | |
| High Activity | 45-120 minutes | 6-7 times per week | |
| Very High Activity | 2+ hours | Daily |
What Is This Tool?
The BMR Calculator estimates your Basal Metabolic Rate — the number of calories your body burns at complete rest to keep essential functions running. Enter your gender, age, height, and weight in metric or imperial units, and choose one of three formulas: Mifflin St Jeor, Revised Harris-Benedict, or Katch-McArdle, the last of which also uses your body fat percentage. Alongside the BMR figure, the tool shows estimated daily calorie needs across six activity levels, from no exercise to very high, and the result can be downloaded as a PDF. It is an informational estimate, not medical or nutritional advice.
How to Use This Tool?
- Select your gender and your preferred units, metric or imperial.
- Enter your age, height, and weight.
- Optionally choose a formula, and a body fat percentage if you pick Katch-McArdle.
- Click Calculate, then download the result as a PDF if needed.
Key Features
- Estimates Basal Metabolic Rate using three formulas: Mifflin St Jeor, Revised Harris-Benedict, and Katch-McArdle.
- Shows estimated daily calorie needs across six activity levels, from no exercise to very high.
- Accepts gender, age, height, and weight, with a metric and imperial toggle.
- Uses body fat percentage for a leaner estimate when the Katch-McArdle formula is selected.
- Download the BMR and activity breakdown as a PDF.
Examples
- A 30-year-old man at 182 cm and 80 kg, using Mifflin St Jeor, has a BMR of about 1,793 calories per day.
- At a light activity level, that same person needs roughly 2,626 calories per day.
- Switching to Katch-McArdle bases the estimate on lean mass using the entered body fat percentage.
- Choosing female applies a different constant in the formula, lowering the BMR estimate.
Common Use Cases
- Finding a daily calorie target for maintaining current weight.
- Planning calorie intake for gradual weight loss or gain.
- Comparing how the three formulas estimate the same person's BMR.
- Supporting fitness and nutrition tracking with a baseline number.
- Understanding how activity level changes total daily calorie needs.
Tips & Best Practices
- Use an accurate, recent weight for a more reliable estimate.
- Choose Katch-McArdle only if you have a trustworthy body fat percentage.
- Pick the activity level that honestly reflects your typical week.
- Treat the result as a starting estimate and adjust based on real-world results.
- Recalculate periodically, since BMR changes as your weight and age change.
Limitations
- It provides an estimate; actual metabolism varies between individuals.
- It accepts ages from 15 to 80, so values outside that range are not supported.
- Except for the body fat input in Katch-McArdle, it does not account for muscle mass, medical conditions, or medications.
- It is for general information only and is not medical or nutritional advice.
Frequently Asked Questions
- What is Basal Metabolic Rate?
- It is the number of calories your body uses at complete rest to maintain basic functions like breathing, circulation, and temperature.
- Which formula should I choose?
- Mifflin St Jeor is a widely used general estimate, Revised Harris-Benedict is an alternative, and Katch-McArdle is best if you know your body fat percentage.
- What does the activity table show?
- It multiplies your BMR by activity factors to estimate total daily calorie needs at six levels, from no exercise to very high.
- Can I save my result?
- Yes. Click Download Result as PDF to save your BMR and the activity breakdown as a file.
Key Terminology
- Basal Metabolic Rate (BMR)
- The calories your body burns at complete rest to keep essential functions running.
- Total Daily Energy Expenditure (TDEE)
- Your BMR multiplied by an activity factor, estimating the calories you burn in a full day.
- Mifflin St Jeor
- A widely used formula that estimates BMR from weight, height, age, and gender.
- Katch-McArdle
- A formula that estimates BMR from lean body mass using your body fat percentage.
- Body fat percentage
- The share of your total body weight that is fat, used by the Katch-McArdle formula.