BMR Calculator
Estimate your Basal Metabolic Rate (BMR) with science-backed formulas and optionally view your TDEE based on activity level.
This tool is part of our broader health calculator collection. You may also find our adult BMI calculator and child & teen BMI calculator useful, or explore all tools in our Health Calculators hub.
- Mifflin–St Jeor (recommended): best default for most adults.
- Harris–Benedict (revised): classic option; may slightly overestimate.
- Katch–McArdle: best if you know your body fat % (uses lean body mass).
Your Details
Your Results
Assumptions & Warnings
📊 BMR vs TDEE Comparison
📋 Detailed Breakdown
| Parameter | Value |
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| Enter your details to see the breakdown. | |
How to Use This BMR Calculator
- Select your formula: If you’re unsure, choose Mifflin–St Jeor (recommended for most adults).
- Choose your unit system: Metric (kg, cm) or US (lb, ft/in).
- Enter your details: Age, sex, weight, and height (or body fat % for Katch–McArdle).
- Pick an activity level (optional): This calculates your TDEE (maintenance calories).
- Review results: Use BMR as your “at-rest” estimate; use TDEE for day-to-day calorie planning.
If you want a quick weight status check, try our BMI calculator.
Understanding BMR and TDEE
BMR (Basal Metabolic Rate) estimates how many calories your body needs each day to maintain vital functions at complete rest (breathing, circulation, temperature regulation).
TDEE (Total Daily Energy Expenditure) estimates your daily maintenance calories by adjusting your BMR for activity level. In practice, most people use TDEE (not BMR) to plan calories.
- Maintain weight: Eat roughly your TDEE
- Lose weight: Often a 300–500 kcal/day deficit is used
- Gain weight: Often a 300–500 kcal/day surplus is used
For children and teens, use our Child & Teen BMI Calculator instead of adult BMI categories.
About the Formulas
This BMR calculator includes three widely used equations. No formula is perfect for everyone, but these are common in nutrition and fitness tools.
Mifflin–St Jeor (Recommended)
Often considered the best general-purpose option for adults. Uses sex, age, weight, and height.
Harris–Benedict (Revised)
A classic equation (revised version). It can slightly overestimate BMR for some people, but it’s still widely referenced.
Katch–McArdle
Uses lean body mass (derived from your body fat %) and can be useful for athletic or muscular individuals—if body fat % is reasonably accurate.
Frequently Asked Questions
General guidance. Consult a qualified professional for personalized advice.
Q1: What is BMR?
Answer: BMR (Basal Metabolic Rate) is an estimate of how many calories your body burns each day at complete rest to support vital functions like breathing, circulation, and temperature regulation.
Q2: What is the difference between BMR and TDEE?
Answer: BMR is calories burned at rest. TDEE (Total Daily Energy Expenditure) adjusts BMR for your activity level to estimate your daily maintenance calories. Most people use TDEE for meal planning.
Q3: Which BMR formula should I use?
Answer: For most adults, Mifflin–St Jeor is a good default. Use Harris–Benedict (Revised) if you want a classic comparison. Use Katch–McArdle if you have a reasonably accurate body fat % estimate.
Q4: How accurate is a BMR calculator?
Answer: These formulas provide estimates and can be off due to genetics, hormones, body composition, medications, and health conditions. For a precise measurement, labs may use indirect calorimetry.
Q5: Why does the calculator ask for sex?
Answer: Mifflin–St Jeor and Harris–Benedict include sex because average body composition differs between males and females, which affects estimated energy needs. Katch–McArdle doesn’t require sex because it uses lean body mass instead.
Q6: How do I estimate body fat % for Katch–McArdle?
Answer: Common methods include BIA smart scales, skinfold calipers, DEXA scans, or professional body composition testing. Home estimates can vary, so treat results as approximate.
Q7: Should I use BMR or TDEE to lose weight?
Answer: Use TDEE for planning daily intake. BMR is an “at-rest” estimate, while TDEE accounts for activity. Many people start with a moderate deficit (such as 300–500 kcal/day), then adjust based on progress.
Sources & Further Reading
These references support the formulas and concepts used in this calculator.
Mifflin MD, et al. (1990) — A new predictive equation for resting energy expenditure in healthy individuals Roza AM, Shizgal HM (1984) — The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass Basal metabolic rate (BMR): Definition, importance, and how to calculate it NCBI Bookshelf — Energy Requirements: Assessment Using Predictive Equations MedlinePlus — Understanding calorie needs and energy balance CDC — Healthy weight, calorie balance, and daily energy needs