AkCalculators

Basal Energy Expenditure (BEE) — what it is, which equations to use, and how to interpret results

Basal energy expenditure (BEE), often called basal metabolic rate (BMR), represents the energy the body requires at rest to maintain essential physiological processes such as respiration, circulation, cell maintenance and thermoregulation. Accurately estimating BEE helps design nutrition plans, clinical feeding regimens, and sports nutrition strategies. Because direct measurement via indirect calorimetry is not always available, predictive equations offer practical estimates — each equation has strengths, limitations and specific population origins. This guide explains common equations, how to use them, and how to apply results responsibly.

Common predictive equations

This calculator offers three widely-used equations:

• Mifflin–St Jeor (1990) — considered accurate for modern populations; uses weight (kg), height (cm) and age. Equations:

  Men: 10×weight + 6.25×height − 5×age + 5
  Women: 10×weight + 6.25×height − 5×age − 161

• Revised Harris–Benedict (1984) — updated from older work and still commonly used:

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

• Schofield equations — provide age- and sex-specific coefficients derived from population studies (often used in clinical and policy settings). This calculator applies the standard Schofield formulas for the relevant age bracket.

When to use multiple formulas

Different formulas were developed on different sample populations (age ranges, ethnicities, body compositions). Comparing outputs from multiple equations gives a sense of variability; use the range as a guide when planning energy targets. For clinical care, if precise energy needs are critical (e.g., critically ill patients, malnutrition), measured resting energy expenditure is preferred.

From BEE to daily calorie targets

BEE is the baseline. To estimate total daily energy expenditure (TDEE) multiply BEE by an activity factor that reflects typical daily activity:

• Sedentary (little or no exercise) — ×1.2
• Light activity (light exercise 1–3 days/week) — ×1.375
• Moderate activity (3–5 days/week) — ×1.55
• High activity (6–7 days/week) — ×1.725
• Very heavy activity (athletes, manual labour) — ×1.9

Practical considerations and limitations

Predictive formulas assume typical body composition for the given inputs. For muscular athletes or people with significant sarcopenia, predictions can be biased. Use measured weight, consistent unit inputs, and, where possible, body composition data (fat-free mass) for greater precision. Also, state factors such as illness, fever, or thyroid disease alter metabolic rate substantially.

Tips for use

• Enter measured weight where possible — if you need to approximate, use clinical scales rather than self-reported values.
• Compare multiple equations and consider the median or range when setting targets.
• Monitor response and adjust calorie targets based on measured weight change and well-being rather than relying on a single estimate forever.

Disclaimer: This calculator provides estimates for informational use and is not a replacement for clinical assessment or indirect calorimetry. For medical nutrition therapy consult a registered dietitian or physician.