This BMR calculator estimates basal metabolic rate in kilocalories per day using the Mifflin-St Jeor equation from sex, age, weight, and height. BMR is a resting metabolism estimate for education and personal tracking. It is not a diagnosis, meal plan, or medical advice.
BMR is a resting metabolism estimate. It is not a meal plan, not a diagnosis, and not medical advice. People use it as a starting reference before thinking about total daily needs with activity. If you need activity adjusted targets, use a calorie style calculator after you understand BMR.
Explore related tools in health calculators, nutrition, and fitness. Everyday helpers sit in everyday math. The calculators archive lists all options.
What this BMR calculator estimates
Inputs are gender, age, weight (kg), and height (cm). Output is BMR in kcal/day, rounded in the interface. The estimate reflects the Mifflin St Jeor model for adults in typical calculator ranges.
Searchers often type Harris Benedict because that older equation is widely taught. MultiCalify implements Mifflin St Jeor instead, which is a common modern default in many online tools. Knowing which equation a page uses prevents false comparisons between sites.
Who it helps
- People learning what basal metabolic rate means
- Users comparing resting burn estimates before activity adjustments
- Students checking Mifflin St Jeor examples
- Anyone who wants a free online bmr calculator without registration
How to enter height, weight, age, and sex for BMR
- Select male or female for the equation constant.
- Enter age in years.
- Enter body weight in kilograms.
- Enter height in centimeters.
- Read BMR as kcal per day.
Convert pounds to kilograms and feet or inches to centimeters before entry if your measurements are imperial. A unit converter can help with those steps. Wrong units are the most common source of large BMR errors.
Mifflin St Jeor formula used here
Male: BMR = 10 × weight(kg) + 6.25 × height(cm) – 5 × age + 5
Female: BMR = 10 × weight(kg) + 6.25 × height(cm) – 5 × age – 161
Where:
- weight is in kilograms
- height is in centimeters
- age is in years
- BMR is kilocalories per day in this model
The live script returns the raw equation value, then the UI rounds to a whole number for display.
BMR Calculator Formula and Daily Calorie Needs
Basal metabolic rate (BMR) is the number of calories your body burns at complete rest. This calculator uses the Mifflin-St Jeor equation (1990), which research reviews have found to be the most accurate common formula for most adults:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Example: a 30-year-old man weighing 70 kg at 175 cm tall: 700 + 1,093.75 − 150 + 5 = 1,649 kcal/day. A 30-year-old woman weighing 60 kg at 165 cm tall: 600 + 1,031.25 − 150 − 161 = 1,320 kcal/day.
From BMR to daily calories (TDEE)
| Activity level | Multiply BMR by |
|---|---|
| Sedentary (little exercise) | 1.2 |
| Light (1–3 days/week) | 1.375 |
| Moderate (3–5 days/week) | 1.55 |
| Very active (6–7 days/week) | 1.725 |
| Extra active (physical job + training) | 1.9 |
For the man in the example, moderate activity gives 1,649 × 1.55 ≈ 2,556 kcal/day to maintain his weight. Any result is an estimate, typically within about 10% for most people, and is less accurate for very muscular people or people with obesity. Don’t eat below your BMR without medical advice.
Worked example
Male, age 30, weight 70 kg, height 170 cm.
- BMR = 10×70 + 6.25×170 – 5×30 + 5
- BMR = 700 + 1062.5 – 150 + 5
- BMR = 1617.5 kcal/day (about 1618 when rounded)
| Input | Value |
|---|---|
| Gender | Male |
| Age | 30 |
| Weight | 70 kg |
| Height | 170 cm |
| BMR | About 1618 kcal/day |
Female example with the same age, weight, and height: BMR = 700 + 1062.5 – 150 – 161 = 1451.5 kcal/day (about 1452 rounded). The constant difference between equations is large enough to matter for planning discussions.
BMR by Age: Mifflin-St Jeor Examples
Estimated BMR in kcal/day for the same height and weight at different ages. Each decade lowers the estimate by 50 kcal, because the equation subtracts 5 kcal per year of age.
| Profile | Age 20 | Age 30 | Age 40 | Age 50 | Age 60 |
|---|---|---|---|---|---|
| Man, 70 kg, 175 cm | 1,699 | 1,649 | 1,599 | 1,549 | 1,499 |
| Man, 85 kg, 180 cm | 1,880 | 1,830 | 1,780 | 1,730 | 1,680 |
| Woman, 60 kg, 165 cm | 1,370 | 1,320 | 1,270 | 1,220 | 1,170 |
| Woman, 70 kg, 165 cm | 1,470 | 1,420 | 1,370 | 1,320 | 1,270 |
How Accurate Is a BMR Calculator?
Mifflin-St Jeor was developed in 1990 from 498 healthy adults aged 19–78 whose resting energy use was measured. A 2005 systematic review found it the most reliable of the common equations: it lands within 10% of measured resting metabolic rate for more people than Harris-Benedict, Owen or WHO. A later study of 337 adults found 82% of estimates within 10% (87% in non-obese and 75% in obese adults). In adults with severe obesity it tended to underestimate. So treat your result as a starting point that may be off by 10% or more, not as a measurement. Only indirect calorimetry measures BMR directly. To estimate your non-fat mass, use the lean body mass calculator, then plan a target with the calorie deficit calculator.
This is an educational estimate, not medical advice. Talk to a GP, doctor or registered dietitian before changing how you eat, especially if you are pregnant, under 18 or have a health condition.
BMR versus calorie needs and TDEE
BMR alone assumes rest. Daily life includes walking, work, and exercise. Total daily energy expenditure estimates apply activity factors or other models on top of BMR. Multicalify’s calorie calculator multiplies BMR by an activity factor for that style of estimate.
Keep pages distinct in your reading: BMR for resting baseline, calorie tools for intake targets with activity. Using BMR as if it were a full day budget can understate needs for active people.
Harris Benedict versus Mifflin St Jeor
Harris Benedict is an older resting energy equation set that still appears in textbooks and search queries. Mifflin St Jeor uses different coefficients and constants. Results will not match across equations even with identical inputs. This page stays aligned with the live Mifflin St Jeor implementation.
Body composition and equation limits
Two people can share the same sex, age, weight, and height yet differ in muscle and fat. Equation based BMR does not see composition directly. That is one reason lab measured resting metabolic rate can disagree with calculator output. Treat the number as a structured estimate for learning and rough planning, then adjust with professional guidance when stakes are high.
Age enters with a negative coefficient, so older ages reduce estimated BMR when other inputs stay fixed. Weight and height scale the estimate upward as they increase. Those directional effects are features of the formula, not personalized clinical findings.
How to interpret the result
Treat BMR as an educational estimate of resting burn, not a lab measurement. Individual thyroid status, body composition, and health conditions can shift true needs. Do not use the number to diagnose illness or to justify extreme intake restriction.
If you are changing diet or training hard, consult a qualified professional. Online calculators cannot examine you and cannot replace clinical judgment.
BMR mistakes that inflate or understate calorie needs
- Entering pounds in a kilograms field
- Entering height in inches when centimeters are required
- Comparing this BMR with a Harris Benedict result as if formulas matched
- Using BMR as a full day calorie target without activity
- Assuming the estimate is a medical measurement
- Ignoring that rounding can change the displayed whole number by 1 kcal
- Selecting the wrong gender option for the equation constant
- Expecting wearable devices to match Mifflin St Jeor exactly
Practical scenarios
Learning: verify a textbook Mifflin St Jeor example with the same inputs.
Baseline: estimate resting burn before opening an activity adjusted calorie tool.
Unit prep: convert imperial measurements, then calculate once in metric.
Sensitivity: change weight or age slightly to see how the equation responds.
Compare and contrast: compute BMR, then open a calorie tool to see activity multiplied estimates.
Limitations and disclaimer
This free online bmr calculator uses Mifflin St Jeor with the fields above. It is not medical advice, not a clinical RMR test, and not a promise of personal calorie needs. Pregnant people, adolescents outside the intended adult use patterns, and people with medical conditions need personalized care from licensed professionals.
Related tools
Continue with nutrition and body tools under nutrition, health, and fitness. Everyday converters that help with units are in everyday calculators. See the archive for the complete list.
How to read your BMR result responsibly
Treat the number as a baseline resting estimate. Recheck inputs if units were mixed, then use related health calculators for activity-adjusted planning. Speak with a clinician for medical nutrition decisions.
How to get better results from this calculator
Start with realistic inputs you can verify from a quote, statement, or plan. Then change one variable at a time so you can see which assumption moves the result the most. Save or write down the scenarios you care about before you talk to a lender, advisor, or service provider.
Treat the output as a planning estimate for the bmr tool on this page. Confirm fees, rounding, eligibility rules, and any product specific terms with the official source before you make a decision. If two options look close, compare total cost or total benefit, not only the headline result.
BMR versus TDEE and daily calorie targets
BMR estimates energy use at rest. Total daily energy expenditure also includes activity. If you need a daily intake target, start from BMR then adjust for activity with a calorie tool rather than treating BMR as a diet prescription.
Related: Calorie Calculator · BMI Calculator · what is BMR.