resting energy calculator

What is resting energy expenditure?

Resting Energy Expenditure (REE), often called Resting Metabolic Rate (RMR), is the amount of energy your body uses in a day to maintain basic life functions while at rest. This includes breathing, circulation, temperature regulation, cell repair, and brain activity.

REE is your baseline calorie burn. It does not include calories from exercise, walking around all day, or digesting food in a fully detailed way. But it gives you a practical starting point for setting calorie goals.

Why a resting energy calculator is useful

• Weight loss: Helps you set a calorie target below maintenance.
• Muscle gain: Helps you avoid eating too little while training.
• Weight maintenance: Provides a data-based estimate of daily needs.
• Performance nutrition: Helps athletes plan intake around training blocks.

Formulas used in this calculator

1) Mifflin-St Jeor (recommended for most adults)

Many nutrition professionals use this formula because it performs well in general populations.

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

2) Harris-Benedict (revised)

An older, widely known formula with revised constants:

• Men: REE = 88.362 + 13.397×weight + 4.799×height − 5.677×age
• Women: REE = 447.593 + 9.247×weight + 3.098×height − 4.330×age

3) Katch-McArdle

This formula uses lean body mass, so it can be helpful when body fat percentage is known:

• REE = 370 + 21.6×lean body mass(kg)
• Lean body mass = weight × (1 − body fat %/100)

How to interpret your result

Your REE is not your full-day calorie maintenance number. To estimate maintenance calories, multiply REE by an activity factor. This gives a Total Daily Energy Expenditure (TDEE) estimate.

• 1.2: Sedentary lifestyle
• 1.375: Light activity
• 1.55: Moderate activity
• 1.725: High activity
• 1.9: Very high activity

From there, you can adjust calories based on goals:

• Fat loss: Usually 10-25% below maintenance.
• Muscle gain: Usually 5-15% above maintenance.
• Maintenance: Stay near estimated TDEE and monitor trends.

Factors that can shift resting energy needs

Body composition

Muscle tissue is more metabolically active than fat tissue, so people with higher lean mass often have higher resting energy needs.

Age

REE tends to decline with age, partly due to changes in lean mass and hormonal environment.

Sex and hormones

Average differences in body composition and hormonal profiles can influence resting metabolism.

Dieting and adaptation

Long calorie deficits can lower energy expenditure beyond what formulas predict. This is called metabolic adaptation.

Best practices for better accuracy

• Use consistent morning weigh-ins over time.
• Track calorie intake honestly for 2-3 weeks.
• Adjust by real outcomes (scale trend, measurements, performance).
• Recalculate after major weight changes (5-10 lb or 2-5 kg).

Quick FAQ

Is REE the same as BMR?

They are close. BMR is measured under stricter lab conditions. REE/RMR is a practical estimate used in daily coaching and nutrition planning.

What if different formulas give different values?

That is normal. Think of the result as a strong starting range. Your real-world progress tells you how to fine-tune calories.

Can I use this during fat loss?

Absolutely. Recalculate as your body weight changes and adjust intake to keep your weekly rate of progress realistic.

Important note

This calculator is for educational use and general planning. It is not a medical diagnosis tool. If you have thyroid disease, metabolic disorders, pregnancy-related concerns, or other clinical needs, consult a qualified healthcare professional or registered dietitian.