Basal Metabolic Rate (BMR) Calculator
Estimate your Basal Metabolic Rate (BMR) using science-backed formulas. For a full daily-calorie plan, use our TDEE calculator.
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 Maintenance Comparison
🧾 Calculation Steps
📋 Detailed Breakdown
| Parameter | Value |
|---|---|
| Enter your details to see the breakdown. | |
🔧 Embed this calculator
Add this free standards-based calculator to your site — no signup required.
The embed code you copy includes an iframe (height 1020px) and visible attribution to this page: https://calctypes.com/bmr-calculator/
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: Weight and (depending on formula) age, sex, height, or body fat %.
- (Optional) select activity level: This estimates activity-adjusted daily maintenance calories.
- Review results: Use BMR as your “at-rest” estimate; use the activity-adjusted estimate for day-to-day planning.
Want a full plan? Use our TDEE calculator. For a quick weight status check, try our BMI calculator.
Understanding BMR and Daily Calorie Needs
BMR (Basal Metabolic Rate) estimates how many calories your body needs each day to maintain vital functions at complete rest (breathing, circulation, temperature regulation).
Maintenance calories (activity-adjusted) estimate daily needs by adjusting your BMR for activity. Many people use a full TDEE calculator for day-to-day planning.
For children and teens, use our Child & Teen BMI Calculator instead of adult BMI categories.
About the Formulas (Why results differ)
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.
How accurate is this?
A BMR calculator is a starting-point estimate. These formulas are based on averages from research populations, so an individual result can be meaningfully higher or lower than your true resting energy use.
- Expect individual variation: genetics, hormones, sleep, stress, medications, and health conditions can shift real-world needs.
- Input accuracy matters: small errors in height/weight (and especially body fat % for Katch–McArdle) can change the estimate.
- Formula choice matters: Mifflin–St Jeor is a strong default for most adults; Katch–McArdle may be helpful if body fat % is reasonably accurate.
- Maintenance ≠ BMR: the activity-adjusted number is a simplified model (BMR × multiplier), not a guarantee of weight change.
For higher-confidence measurement, ask a qualified clinician about indirect calorimetry (lab testing). For practical planning, use your BMR/TDEE as a baseline, then adjust gradually based on multi-week trends and wellbeing.
This is not medical advice. Full policy: CalcTypes Disclaimer.
Limitations (Important)
- Estimate only: predictive equations can differ from lab testing (indirect calorimetry).
- Population fit varies: accuracy may be lower for teens, pregnancy/lactation, elite athletes, and some medical conditions.
- Body fat % uncertainty: Katch–McArdle is sensitive to body fat % measurement error.
- Not medical advice: not for diagnosis, treatment, or individualized nutrition prescriptions.
- Not for compliance decisions: don’t use this alone for any clearance/compliance requirement.
Full policy: CalcTypes Disclaimer.
Methodology (How We Calculate BMR)
This calculator estimates BMR using published predictive equations and optionally estimates activity-adjusted daily calories by multiplying BMR by an activity factor.
BMR equations used
- Mifflin–St Jeor: uses weight, height, age, and sex.
- Harris–Benedict (Revised): classic alternative equation.
- Katch–McArdle: uses lean body mass (from body fat %).
Important notes
- BMR vs RMR: terms are often used interchangeably; predictive equations may not match either measurement perfectly.
- kJ conversion: we convert using 1 kcal = 4.184 kJ.
- Rounding: results are rounded to the nearest whole kcal/day for readability.
For full daily energy planning, use our TDEE calculator.
Frequently Asked Questions
General guidance. Consult a qualified professional for personalized advice.
2) How do I calculate my BMR?
Most BMR calculators use predictive equations based on your weight, height, age, and sex (or lean body mass if using body fat %). This calculator includes Mifflin–St Jeor, Harris–Benedict (revised), and Katch–McArdle.
3) What is the formula of BMR?
There isn’t a single universal BMR formula. Common options include Mifflin–St Jeor, Harris–Benedict (revised), and Katch–McArdle (uses lean body mass from body fat %).
4) What is the best BMR formula?
For most adults, Mifflin–St Jeor is a strong default. Harris–Benedict (revised) is a common classic alternative for comparison. Katch–McArdle can be useful if your body fat % estimate is reasonably accurate.
5) What is the Mifflin–St Jeor equation (BMR formula)?
Men: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5
Women: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161
6) What is the Harris–Benedict equation (revised)?
Men: BMR = 88.362 + 13.397×weight(kg) + 4.799×height(cm) − 5.677×age
Women: BMR = 447.593 + 9.247×weight(kg) + 3.098×height(cm) − 4.330×age
7) What is the Katch–McArdle BMR formula (body fat % option)?
Katch–McArdle uses lean body mass (LBM):
LBM = weight(kg) × (1 − bodyFat%/100)
BMR = 370 + 21.6 × LBM(kg)
If body fat % is inaccurate, the BMR estimate will be inaccurate.
8) Why does the calculator ask for sex?
Mifflin–St Jeor and Harris–Benedict include sex because average body composition differs between males and females, which affects predicted energy needs. Katch–McArdle doesn’t require sex because it’s based on lean body mass.
9) What’s the difference between BMR and TDEE?
BMR is calories burned at rest. TDEE (Total Daily Energy Expenditure) adjusts BMR for your activity level to estimate daily maintenance calories. Most people use TDEE for meal planning.
10) What’s the difference between BMR and RMR (resting metabolic rate)?
BMR is measured under stricter “basal” conditions (fully rested, fasted, neutral temperature). RMR is measured under less strict conditions, so it’s often slightly higher. Many “BMR calculators” estimate resting energy needs and may be labeled BMR or RMR.
11) How accurate is a BMR calculator?
BMR formulas provide estimates and can differ from your true energy expenditure due to genetics, hormones, body composition, sleep, stress, medications, and health conditions. For a more direct measurement, labs may use indirect calorimetry.
12) What is the correct BMR for my age?
There isn’t one “correct” BMR for an age group. BMR depends on body size, lean mass, sex, and other factors—age is only one input in predictive equations.
13) What is a good BMR for a man?
BMR isn’t a “good vs bad” score. It’s an estimate of baseline energy needs and varies with height, weight, and lean mass. For practical planning, many people focus more on TDEE (maintenance calories) and long-term trends.
14) How do you calculate a man’s BMR (or a woman’s BMR)?
Use the same formula family (e.g., Mifflin–St Jeor or Harris–Benedict), but the equation uses a different constant for men vs women. This calculator applies the correct version automatically when the selected formula uses sex.
15) How much should I eat to lose weight if my BMR is 1400?
BMR is an at-rest estimate and usually isn’t a recommended intake target. For weight planning, people typically start from TDEE (maintenance calories) and adjust by a moderate deficit while monitoring progress and wellbeing. If you’re unsure what’s appropriate for you, consult a qualified clinician or registered dietitian.
16) How do I estimate body fat % for Katch–McArdle?
Common methods include BIA smart scales, skinfold calipers, DEXA scans, and professional assessments. Home estimates can vary significantly, so treat results as approximate.
17) Does this BMR calculator work in kg (metric) and show kJ/day? (BMR calculator kg / India)
Yes. You can switch between Metric (kg, cm) and US (lb, ft/in). Results display in kcal/day and also convert to kJ/day.
18) Can I use this BMR calculator during pregnancy or breastfeeding?
Use caution. Standard BMR equations aren’t designed to fully account for pregnancy or lactation energy needs. For personalized guidance, consult a qualified healthcare professional.
19) Is this BMR calculator for kids or teens?
These formulas are primarily designed for adults. For children and teens, energy needs differ due to growth and development; consider pediatric-appropriate guidance and professional advice if needed.
20) Does this calculator also calculate BMI or ideal body weight (IBW)?
No. This page focuses on BMR (and an optional activity adjustment). For weight status, use a BMI calculator. For IBW, use a dedicated ideal body weight tool if available.
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