🔥 Basal Metabolic Rate (BMR) Calculator

Estimate your basal metabolic rate (calories burned at rest) and daily calorie needs (TDEE) using the Mifflin–St Jeor equation. Useful for weight loss, maintenance, and nutrition planning.

This calculator uses the Mifflin–St Jeor equation to estimate BMR, then multiplies by an activity factor to estimate Total Daily Energy Expenditure (TDEE).

What is Basal Metabolic Rate (BMR)?

BMR is the number of calories your body requires to maintain basic physiological functions while at rest — breathing, circulation, cell production, and temperature regulation. It represents the baseline energy requirement and is influenced by age, sex, body composition, height, and genetics.

How BMR differs from Resting Metabolic Rate (RMR)

RMR is similar to BMR but measured under less strict conditions. BMR is usually measured after a full night's sleep and in a fasted state, whereas RMR can be slightly higher since the person may not have fasted or rested completely.

The Mifflin–St Jeor equation

The Mifflin–St Jeor equation is widely used and considered accurate for modern populations. The formulas are:

Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5

Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

For individuals who prefer pounds and inches, this calculator accepts lb and in and converts them automatically to metric units.

Estimating daily calorie needs (TDEE)

BMR accounts for the energy needed at rest. To determine how many calories you burn in a day, multiply BMR by an activity factor to get TDEE (Total Daily Energy Expenditure). Activity multipliers are approximate averages used to capture daily movement and exercise level.

Activity factors

  • Sedentary (×1.2): Little or no exercise — mostly sitting work or lifestyle.
  • Lightly active (×1.375): Light exercise or sports 1–3 days/week.
  • Moderately active (×1.55): Moderate exercise or sports 3–5 days/week.
  • Very active (×1.725): Hard exercise 6–7 days/week.
  • Extra active (×1.9): Very hard exercise, physical job, or training twice daily.

How to use BMR and TDEE for goals

If your goal is to lose weight, create a calorie deficit. A common recommendation is a deficit of 500 kcal/day to lose about 0.45 kg (1 lb) per week. For gaining weight, add calories above maintenance (e.g., +250–500 kcal/day depending on how quickly you want to gain).

Practical example

Jane is a 30-year-old woman, 165 cm tall, weighing 68 kg. Using the Mifflin–St Jeor equation: BMR ≈ (10×68) + (6.25×165) − (5×30) − 161 = 680 + 1031.25 − 150 − 161 ≈ 1400 kcal. If she is moderately active (×1.55), her estimated TDEE ≈ 1400 × 1.55 ≈ 2170 kcal/day.

Accuracy and limitations

Equations like Mifflin–St Jeor provide reasonable estimates for most adults, but individual variation can be significant. Factors that can change actual energy needs include body composition (muscle burns more than fat), hormonal status, medical conditions, medications, and genetics. Direct measurements (e.g., indirect calorimetry) provide more accurate BMR values but are less accessible.

When to adjust your calorie targets

Track progress for 2–4 weeks and adjust based on results. If weight is not changing as expected, consider recalculating after changes in body weight or activity. Also consider non-caloric factors such as sleep, stress, and dietary composition that affect metabolism.

Tips to support metabolic health

  • Maintain or build lean muscle through resistance training — muscle increases resting energy expenditure.
  • Eat adequate protein to support muscle and satiety.
  • Avoid extreme calorie restriction which can lower metabolic rate over time.
  • Prioritize sleep and stress management — both influence metabolic hormones.
  • Stay active throughout the day — incidental movement contributes to daily energy burn.

Common misconceptions

Many people overestimate their calorie burn from exercise and underestimate portion sizes. Another myth is that certain foods (e.g., specific superfoods) dramatically boost BMR — while some foods have a small thermic effect, long-term calorie balance drives weight change.

Summary

The BMR and TDEE estimates provided here are tools to help guide nutritional planning and goal setting. Use them as starting points, monitor progress, and adjust based on real-world results. Consult a registered dietitian or healthcare professional for personalized advice, especially if you have medical conditions.

Frequently Asked Questions (FAQs)

Indirect calorimetry (measuring oxygen consumption and CO₂ production) in a clinical setting is the gold standard. Equations are practical estimates for everyday use.
No. BMR is calories burned at rest. Total daily calories include activity, digestion (thermic effect of food), and non-exercise activity thermogenesis (NEAT).
Either is fine — this calculator accepts both and converts to metric internally. Ensure you enter units correctly for accurate results.
Recalculate when you experience meaningful weight change (e.g., every 5–10% bodyweight change) or when your activity pattern changes significantly.
TDEE is an estimate. Use it as a starting point and track progress. For precise meal planning, consider professional guidance and tracking actual intake and weight changes.
Yes — more lean muscle increases BMR because muscle tissue requires more energy at rest than fat tissue.
BMR varies. Factors like age, low body weight, hypothyroidism, or previous caloric restriction can lower BMR. Consult a healthcare provider if concerned.
You can modestly increase resting energy expenditure by building muscle, staying active, and avoiding prolonged very-low-calorie diets. Changes are gradual.
Yes. Some medications and medical conditions can alter metabolism. Discuss medications with your healthcare provider if you notice metabolic changes.
No. This is an educational calculator. Consult a registered dietitian or healthcare professional for personalized medical or nutrition advice.