BMR Calculator (Basal Metabolic Rate)

Use the BMR Calculator

Enter age, sex, height, and weight to estimate your basal metabolic rate (BMR). The BMR calculator supports Mifflin–St Jeor and revised Harris–Benedict formulas and can show TDEE with an activity level.

How to Use BMR Calculator (Basal Metabolic Rate)

1. Step 1: Enter age and sex

   Provide your age in years and select male or female.

2. Step 2: Pick units

   Choose Metric (cm, kg) or US (ft/in, lb) and enter height and weight.

3. Step 3: Select formula

   Use Mifflin–St Jeor (default) or switch to revised Harris–Benedict.

4. Step 4: Add activity level

   Optional: pick your daily activity to see estimated TDEE.

5. Step 5: View BMR and targets

   Read your BMR, TDEE, and suggested calorie targets for goals.

Key Features

• Mifflin–St Jeor & Harris–Benedict
• TDEE with activity levels
• Metric and US units
• Age and sex adjustments

Understanding Results

BMR calculator tips for accurate entries

Measure height without shoes, use a recent morning body weight, and choose the activity level that best matches most days, not your best or worst day. Small input errors can shift a basal metabolic rate calculator result by a noticeable amount.

Formula

Your basal metabolic rate (BMR) is estimated using your age, sex, height, and weight. We provide two well-validated options: Mifflin–St Jeor (1990) and the revised Harris–Benedict (1984). Both formulas return calories per day that your body would use at rest. In plain terms: bigger bodies and younger ages usually mean higher BMR, while smaller bodies and older ages lower BMR.

• Mifflin–St Jeor (male): BMR = 10×kg + 6.25×cm − 5×age + 5
• Mifflin–St Jeor (female): BMR = 10×kg + 6.25×cm − 5×age − 161
• Harris–Benedict (revised, male): BMR = 88.362 + 13.397×kg + 4.799×cm − 5.677×age
• Harris–Benedict (revised, female): BMR = 447.593 + 9.247×kg + 3.098×cm − 4.330×age

If you select an activity level, we multiply your BMR by a standard activity factor to estimate total daily energy expenditure (TDEE). That number approximates your daily calorie needs on a typical day.

Prefer a different phrasing? You can think of the Mifflin–St Jeor calculator and the Harris–Benedict calculator as two lenses on the same thing. Both are basal metabolic rate calculator methods; results usually land within a few percent of each other for the same inputs.

Worked example and sanity checks

Example: a 30‑year‑old female at 165 cm and 65 kg using Mifflin–St Jeor has BMR ≈ 10×65 + 6.25×165 − 5×30 − 161 ≈ 1,383 kcal/day. If she selects a light activity level (×1.375), TDEE ≈ 1,900 kcal/day. A modest calorie deficit of ~300–400 kcal/day would target gradual weight loss; a small surplus of ~200–300 kcal/day supports slow weight gain. These are planning numbers — track progress, hunger, and training to adjust.

If your output seems off, re‑check units (centimeters vs inches, kilograms vs pounds) and ensure height and weight are up to date. Remember that long‑term dieting can temporarily lower energy needs via adaptation. Use the BMR calculator as a starting point, then course‑correct with real‑world measurements like scale trends, waist, and performance.

Reference Ranges & Interpretation

BMR values vary widely. For example, a 30-year-old person at 170 cm and 70 kg typically falls around 1,500–1,700 kcal/day depending on sex and formula. Differences of a few percent between Mifflin–St Jeor and revised Harris–Benedict are normal. Focus on trends: as your weight or activity changes, your energy needs change. If you plan weight loss, a modest deficit from TDEE (e.g., 300–500 kcal/day) is a common starting range. For weight gain, a small surplus (e.g., 200–300 kcal/day) is typical.

Our calorie calculator and maintenance calorie calculator can help translate BMR and TDEE into daily targets. For nutrition planning, explore the macro calculator or check your ideal body weight and lean body mass for context.

Assumptions & Limitations

Equations are population averages. They do not capture illness, extreme body composition, or metabolic adaptations from long‑term dieting. Performance athletes and people with high muscle mass may prefer formulas that factor body fat or measured resting energy expenditure. Use results as a starting point for planning, track progress, and adjust gradually. This tool provides information only and is not medical advice.

Complete Guide: BMR Calculator (Basal Metabolic Rate)

Your body burns energy even when you are doing nothing at all. That baseline cost is called your basal metabolic rate (BMR), and it reflects the calories your cells need to keep you alive: breathing, circulation, temperature regulation, and constant repair. Our calculator estimates BMR using the two most cited, modern equations and then extends it to TDEE (total daily energy expenditure) with practical activity factors. It is designed to be fast on mobile, easy to read, and clear about assumptions so you can make informed choices.

What is basal metabolic rate (BMR)?

BMR is the energy your body requires to operate at rest in a thermoneutral environment, typically measured after an overnight fast. It is not a guess about how active you are—it’s the foundational burn rate your body maintains even if you stayed in bed all day. BMR is influenced by your body size, body composition, age, sex, and genetics, with higher lean mass generally increasing energy requirements.

Because measuring true BMR in a lab is time‑consuming, nutrition and fitness planning often rely on predictive equations. These equations use age, sex, height, and weight to estimate BMR with reasonable accuracy for most people. You can then multiply by an activity factor to estimate how many calories you burn in a typical day.

Which BMR formula is most accurate?

Two equations dominate modern use. The Mifflin–St Jeor equation (1990) tends to perform well in contemporary populations and is widely recommended in dietetics. The revised Harris–Benedict equation (1984) updates the classic 1918–1919 Harris–Benedict formula and still provides similar results in practice. Differences between these formulas are usually modest; try both and focus on trends in your weight and how you feel.

For athletes or people with unusually high muscle mass, formulas that use lean body mass (for example, Katch–McArdle) may track your needs more closely. If that’s you, estimate body fat with our body fat percentage calculator and then consider tools built around lean mass.

Peer‑reviewed references: Mifflin MD et al., 1990; Roza AM & Shizgal HM, 1984 (revised Harris–Benedict). Abstracts are available on PubMed for transparency and further reading. Mifflin–St Jeor (1990) • Roza & Shizgal (1984)

How to use the calculator (step‑by‑step)

This tool is mobile‑first. Start by entering your age and choosing male or female. Select Metric or US units and enter your height and weight. Pick a formula (Mifflin–St Jeor is a reliable default) and optionally choose an activity level to see TDEE. The results area shows your BMR (kcal/day), estimated TDEE, and suggested starting calorie targets for weight loss or gain.

For planning, try our companion tools: the calorie calculator translates your goal into daily targets; the macro calculator turns calories into protein, carbs, and fat; and the maintenance calorie calculator estimates your steady‑weight intake from another angle.

• Update inputs as your body changes—energy needs are dynamic.
• Pick the activity level that reflects your actual week, not your aspirations.
• Re‑estimate every few months or after a 5–10% weight change.

TDEE and activity levels

TDEE multiplies your BMR by an activity factor to approximate a typical day’s burn. “Sedentary” reflects mostly seated work and little structured exercise. “Light” covers a few sessions per week or a job with regular walking. “Moderate” fits most people who exercise 3–5 days per week. “Active,” “Very,” and “Extra” correspond to demanding training or physically intensive jobs.

These factors are averages, not laws. If your weight trend suggests your estimate is off—steady gain when you expected maintenance, for example—nudge your intake up or down by 100–200 kcal and reassess after two weeks. Tools like our adult BMI calculator and ideal body weight calculator can provide helpful context.

Example calculations

Consider two examples using Mifflin–St Jeor. Example 1: male, age 30, 178 cm, 75 kg. BMR ≈ 10×75 + 6.25×178 − 5×30 + 5 = 750 + 1112.5 − 150 + 5 ≈ 1717 kcal/day. If he is moderately active (×1.55), TDEE ≈ 2660 kcal/day.

Example 2: female, age 35, 165 cm, 62 kg. BMR ≈ 10×62 + 6.25×165 − 5×35 − 161 = 620 + 1031.25 − 175 − 161 ≈ 1315 kcal/day. With a light activity factor (×1.375), TDEE ≈ 1808 kcal/day. Small day‑to‑day fluctuations in weight are normal—look for weekly trends.

From BMR to calorie targets

Once you have TDEE, create a small gap to drive progress while preserving energy and recovery. For weight loss, many people start 300–500 kcal below TDEE; for weight gain, 200–300 kcal above is common. Track your averages for two weeks, then adjust in 100–200 kcal steps based on trend and how you feel. For a fully guided setup, use our macro calculator to turn that target into macros you can track.

Protein anchors the plan. A common range is 1.6–2.2 g/kg of target body weight, scaled to goals and preference. Carbs and fats can flex based on training and satiety. If you prefer a higher‑fat approach, check the keto macro calculator; if you want a balanced approach, try the calorie intake calculator.

BMR vs. RMR vs. RDEE: what’s the difference?

You may see several abbreviations:

• BMR (Basal Metabolic Rate): theoretical minimum at complete rest and strict conditions.
• RMR (Resting Metabolic Rate): measured under relaxed conditions—slightly higher than BMR.
• RDEE (Resting Daily Energy Expenditure): 24‑hour expansion of RMR; often similar numerically to BMR estimates.

In everyday planning, BMR and RMR are used interchangeably—both are “at rest.” Differences matter for research methods, less so for your tracking notebook. What matters most is that your intake and observed weight trend align.

Common mistakes and how to avoid them

• Overstating activity: choose the level you actually sustain week‑to‑week.
• Never updating: energy needs change with weight, muscle, and training volume.
• Chasing extremes: very large deficits or surpluses make adherence and recovery harder.
• Ignoring protein: adequate protein supports muscle during weight change.
• No feedback loop: track averages for body weight and adjust gradually.

Adjusting when progress stalls

Use a two‑week test. If your average weekly weight change is less than half of the target for two straight weeks, adjust calories by 100–200 per day and keep protein steady. For fat loss, favor a small additional deficit rather than big swings; for gaining, add modestly and prioritize training quality and sleep. Re‑evaluate after another two weeks.

Track simple behavioral anchors too: daily steps, training sessions completed, and bedtime consistency. These often shift outcomes more than micromanaging macros once fundamentals are in place.

Quality‑of‑life guardrails

Choose a plan you can live with. Extreme deficits feel productive in week one but rarely survive real schedules. Keep social meals, plan defaults you enjoy, and aim for a stable routine most days. The calculator provides transparent numbers; your habits turn them into outcomes.

If tracking becomes stressful, scale back to weekly averages and a few anchors that matter to you. Precision is useful, not mandatory — progress comes from consistent, good‑enough decisions.

References and further reading

Predictive equations are a practical middle ground between lab testing and guesswork. If you are undergoing medical treatment, have a complex metabolic condition, or are preparing for competition, consider speaking with a registered dietitian or sports dietitian for individualized guidance.

• Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. PubMed
• Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. PubMed

Keep exploring: estimate your body composition with the lean body mass calculator, sanity‑check height‑adjusted goals with the adult BMI calculator, or plan a balanced intake in minutes with the calorie calculator.

Frequently Asked Questions