SamCalculator

BMR Calculator

Find your Basal Metabolic Rate and see exactly how many calories you need at every activity level.

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What is BMR?

Basal Metabolic Rate (BMR) is the number of calories your body burns per day at complete rest — no movement, no digestion, just the energy needed to keep your heart beating, your lungs breathing, and your cells functioning. It represents 60–75% of total daily calorie burn for most people.

BMR is determined primarily by your body size, muscle mass, age, and sex. Larger, more muscular individuals have higher BMRs because muscle tissue burns more calories than fat even at rest. BMR naturally declines with age as muscle mass decreases — roughly 1–2% per decade after age 30.

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60–75%

of your daily burn

BMR accounts for the majority of calories burned — more than exercise for most people.

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Muscle matters

lean mass drives BMR

Every kg of muscle burns ~13 kcal/day at rest. More muscle = higher BMR.

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Age & BMR

declines 1–2%/decade

Strength training is the most effective way to counter the natural age-related BMR decline.

BMR vs TDEE — What's the Difference?

BMR is only one piece of the puzzle. Your Total Daily Energy Expenditure (TDEE) is what you actually burn each day when you account for movement, exercise, digestion, and daily activity.

MetricDefinitionTypical Share
BMRCalories burned at complete rest60–75%
NEATNon-exercise activity (walking, fidgeting)15–30%
TEFThermic effect of food (digesting meals)8–10%
EATExercise activity thermogenesis5–15%
TDEETotal of all four components100%

Formula: TDEE = BMR × Activity Multiplier. The table above shows your TDEE at five different activity levels — use it to find which matches your lifestyle.

BMR Formulas Explained

Mifflin-St Jeor (Recommended)

Published in 1990. Validated as the most accurate formula for the general population across multiple peer-reviewed studies.

Men: BMR = 10W + 6.25H − 5A + 5

Women: BMR = 10W + 6.25H − 5A − 161

W = weight (kg) · H = height (cm) · A = age (years)

Harris-Benedict (Revised 1984)

The Roza-Shizgal revision of the 1919 original. Historically popular; tends to slightly overestimate BMR compared to Mifflin.

Men: BMR = 88.362 + 13.397W + 4.799H − 5.677A

Women: BMR = 447.593 + 9.247W + 3.098H − 4.330A

Katch-McArdle

Uses lean body mass instead of total weight — the most accurate formula for lean or athletic individuals. Requires body fat % measurement.

BMR = 370 + 21.6 × LBM

LBM (kg) = weight × (1 − body fat % / 100)

Activity Level Descriptions

Choosing the right activity multiplier is the most common source of error in calorie calculations. Most people overestimate their activity level. Be honest — even "light exercise" 3 days a week doesn't qualify as moderate if your job is sedentary.

🪑 Sedentary (×1.2)

You have a desk job or spend most of the day sitting. You do little to no formal exercise. This applies to most office workers who don't exercise regularly.

🚶 Light Exercise (×1.375)

You exercise lightly 1–3 days per week (walking, yoga, light gym). Most of your day is still sedentary. This is the most commonly chosen level.

🏃 Moderate Exercise (×1.55)

You exercise moderately 3–5 days per week with consistent effort — running, cycling, lifting. This is appropriate if you genuinely work out 4–5 times per week at medium intensity.

🏋️ Heavy Exercise (×1.725)

You train hard 6–7 days per week. This applies to competitive athletes, bodybuilders in a prep phase, or people with physically demanding hobbies combined with daily training.

⚡ Athlete Level (×1.9)

You train twice a day or have an extremely physically demanding job (construction, military training). Very few people actually fall in this category.

How to Increase Your BMR

BMR is largely determined by genetics, body size, and age — but it's not fixed. Here are evidence-based strategies to raise your metabolic rate:

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Build muscle mass

Resistance training is the single most effective way to increase BMR long-term. Every kg of muscle adds ~13 kcal/day to your resting burn.

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Eat enough protein

Protein has the highest thermic effect of food (25–30% of calories burned in digestion). High protein intake also preserves muscle during fat loss.

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Stay hydrated

Mild dehydration can suppress resting metabolic rate. Controlled studies report a modest 4–24% short-term increase in resting energy expenditure after drinking ~500 ml of cold water (effects vary by individual).

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Prioritize sleep

Sleep deprivation reduces metabolic rate and dramatically increases hunger hormones (ghrelin up, leptin down). 7–9 hours of quality sleep is essential for metabolic health.

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Caffeine (moderate)

Controlled trials report caffeine increases metabolic rate by 3–11% short-term. Green tea and coffee are the most studied sources. Effects diminish with habitual use.

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Don't crash diet

Severe calorie restriction reduces BMR through metabolic adaptation. Eat at modest deficits (−500 kcal/day max) and include diet breaks to prevent slowdown.

How Many Calories Should You Eat?

Once you know your BMR and TDEE, the right calorie intake depends entirely on your goal:

🔥 Fat Loss

  • • Eat 500 kcal below TDEE for ~0.5 kg/week loss
  • • Don't drop below your BMR
  • • Prioritise protein (35%) to retain muscle
  • • Recalculate every 4 weeks as weight drops

⚖️ Maintenance

  • • Match intake to your TDEE
  • • Best phase for building habits and strength
  • • 30% protein, 40% carbs, 30% fat is balanced
  • • Fluctuate ±100 kcal — don't be rigid

💪 Muscle Gain

  • • Eat 300–500 kcal above TDEE for lean gain
  • • Higher carbs (45%) to fuel training
  • • 0.8–1g protein per lb of bodyweight
  • • Pair with progressive resistance training

Disclaimer: BMR and TDEE values are estimates based on population-average equations. Individual metabolic rates can vary by ±10–15% due to genetics, hormones, gut microbiome, and other factors. Results are for informational purposes only and are not a substitute for advice from a registered dietitian or healthcare provider.

Typical BMR by Age & Sex

BMR declines roughly 1–2% per decade after age 30, primarily because of muscle loss (sarcopenia). The table below shows approximate Mifflin-St Jeor BMR values for an average-build adult (men: 175 cm / 75 kg; women: 162 cm / 62 kg).

Age GroupMen (kcal/day)Women (kcal/day)
19–30~1,750~1,420
31–40~1,700~1,370
41–50~1,650~1,320
51–60~1,600~1,270
61–70~1,550~1,220
71+~1,500~1,170

Values approximated using the Mifflin-St Jeor equation for average-build adults. Use the calculator above for your exact number.

Frequently Asked Questions

BMR (Basal Metabolic Rate) is the number of calories your body burns per day at complete rest — the energy needed to keep your heart beating, your lungs breathing, your brain functioning, and your cells repairing themselves. BMR accounts for roughly 60–75% of total daily calorie burn for most adults and is sometimes used interchangeably with RMR (Resting Metabolic Rate).

The most widely used formula is the Mifflin-St Jeor equation (1990). For men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5. For women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161. The Academy of Nutrition and Dietetics endorses Mifflin-St Jeor as the most accurate predictor for healthy adults.

Typical adult BMR ranges by age — for an average-build adult: 19–30 years, men ~1,700–2,000 kcal/day and women ~1,400–1,650 kcal/day; 31–50 years, men ~1,600–1,900 and women ~1,350–1,550; 51–70 years, men ~1,500–1,800 and women ~1,300–1,500. Taller, more muscular individuals will be at the high end; smaller frames at the low end. There is no universal 'good' number — context is everything.

The Mifflin-St Jeor equation estimates BMR within ±10% of indirect calorimetry (the lab gold standard) for most healthy adults, per a 2005 Academy of Nutrition and Dietetics systematic review. Individual variation from genetics, thyroid function, body composition, and gut microbiome can cause differences. Treat the result as a starting point and adjust based on real-world weight changes tracked over 2–4 weeks.

No. BMR is what you burn at complete rest. TDEE (Total Daily Energy Expenditure) is your full daily burn — BMR multiplied by an activity multiplier (1.2 sedentary to 1.9 extra active). TDEE includes physical activity, exercise, and the thermic effect of food. TDEE is always higher than BMR and is the number you should match for maintenance, eat below for fat loss, or exceed for muscle gain.

BMR and RMR (Resting Metabolic Rate) are closely related but measured slightly differently. BMR is measured after a 12-hour fast, in a completely rested and thermoneutral state, immediately upon waking — strict clinical conditions. RMR is measured under more relaxed conditions (no fasting required, after 15 minutes of rest). RMR is typically 5–10% higher than BMR. In everyday use, BMR and RMR are used interchangeably.

The most evidence-backed strategy is resistance training — each kilogram of lean muscle adds roughly 13 kcal/day to your resting burn. Other supported tactics: eat adequate protein (high thermic effect, preserves lean mass), stay hydrated, prioritize 7–9 hours of sleep, avoid prolonged severe calorie restriction (which triggers adaptive thermogenesis), and use moderate caffeine before workouts (3–11% short-term boost per controlled studies).

No. Eating below your BMR is generally not recommended because BMR is the minimum energy your body needs for vital organ function. Chronically eating below BMR leads to muscle loss, metabolic adaptation (your BMR drops further), nutrient deficiencies, and hormonal disruption. A safe and sustainable deficit is 500–750 kcal below TDEE — not below BMR — producing roughly 0.5–0.75 kg of fat loss per week.

Men typically have more lean muscle mass and less body fat than women of the same weight and height. Muscle tissue is metabolically more active than fat tissue (each kg of muscle burns ~13 kcal/day at rest vs ~4 kcal/day for fat). Hormonal differences also contribute — testosterone promotes muscle growth and metabolic activity, while estrogen supports higher essential body fat. After menopause, this gap narrows somewhat.

The Katch-McArdle formula calculates BMR from lean body mass (LBM) rather than total weight: BMR = 370 + 21.6 × LBM (kg). It's the most accurate formula for lean, muscular, or athletic individuals where total body weight overstates fat-driven metabolic load. You need to know your body fat percentage — use our Body Fat Calculator first to measure it via the US Navy circumference method, or get a DEXA scan for clinical accuracy.

Authors & Editorial Review

Authored By

SamCalculator Editorial Team

Writers and analysts covering evidence-based health and nutrition. Read more on our About page.

Medically Reviewed

Editorial Standards

Every formula, statistic, and recommendation on this page is cross-checked against peer-reviewed research, CDC, NIH, USDA, and Academy of Nutrition and Dietetics publications. Read our full Editorial Policy.

Last reviewed: May 11, 2026

Scientific References

  1. Mifflin MD, St Jeor ST, et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition.
  2. Roza AM, Shizgal HM (1984). The Harris Benedict equation reevaluated. American Journal of Clinical Nutrition.
  3. Academy of Nutrition and Dietetics — Daily calorie needs and BMR estimation.
  4. CDC — Finding a balance of food and activity (calorie & metabolism guidance).
  5. NIH — Body Weight Planner & resting metabolic-rate modeling.
  6. FAO/WHO/UNU (2004). Human Energy Requirements — Expert Consultation report (PAL multipliers).
  7. Pontzer H, et al. (2021). Daily energy expenditure through the human life course. Science.

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