TDEE vs BMR vs Maintenance Calories

The 30-second summary

The three concepts unpacked

BMR (Basal Metabolic Rate) is the energy your body uses to keep you alive while doing nothing — heart pumping, lungs breathing, brain functioning, organs operating, body temperature maintained. Measured under controlled conditions (12-hour fast, supine, in a thermoneutral environment), it accounts for 60–70% of total daily calorie burn for most adults. BMR scales with body mass (especially lean mass), age (drops ~1–2% per decade after 30), and sex.

RMR (Resting Metabolic Rate) is similar to BMR but measured under less strict conditions — typically just at rest, not necessarily after a 12-hour fast. RMR runs about 10% higher than true BMR. Most "BMR calculators" online actually estimate RMR, including the Mifflin-St Jeor equation. The distinction matters in research; for everyday use the two are functionally interchangeable.

TDEE (Total Daily Energy Expenditure) adds everything else: the thermic effect of food (8–10% of daily calories spent digesting), exercise calories burned, and NEAT — non-exercise activity thermogenesis, the most variable component. NEAT alone can vary 2,000 kcal/day between sedentary and active adults (Levine 1999, Mayo Clinic).

Maintenance calories is the layperson term for TDEE — the calorie intake that keeps weight stable. They mean the same thing. The Maintenance Calorie Calculator on this site uses the same Mifflin-St Jeor BMR + activity multiplier formula as the TDEE Calculator. Different framing, identical math.

Head-to-head: BMR vs TDEE vs Maintenance

The three BMR formulas — which to use

Mifflin-St Jeor (1990): the modern standard. Validated by the 2005 Frankenfield et al. systematic review as the most accurate of four BMR equations across 47 studies. Most online calculators default to this. Equation: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 (men) or − 161 (women).

Harris-Benedict (1919, revised 1984): the classic. Still widely used but systematically over-estimates BMR by ~5% — especially in older adults and the obese. The 1984 Roza revision reduced the error but didn\'t eliminate it. Use only if you specifically need the historical formula.

Katch-McArdle (1996): uses lean body mass directly. BMR = 370 + (21.6 × LBM in kg). More accurate than Mifflin-St Jeor for very lean (athletes, low body fat) or very heavy (high body fat) adults, but requires a reliable LBM measurement. For adults with DEXA-measured LBM, prefer Katch-McArdle; for adults without, use Mifflin-St Jeor.

The activity multiplier table

• ×1.2 — Sedentary: desk job, no scheduled exercise
• ×1.375 — Lightly active: light exercise 1–3 days/week
• ×1.55 — Moderately active: exercise 3–5 days/week
• ×1.725 — Very active: exercise 6–7 days/week
• ×1.9 — Extra active: athlete, 2x/day training, manual labour

The multipliers come from the 1985 FAO/WHO/UNU report on energy requirements and have been the standard ever since. Their accuracy: ±10–15% for the population, individual variance mostly driven by NEAT. The 14-day eat-the-prediction calibration is the practical way to find your real maintenance.

Use case: cut, maintain, bulk

• Cut (fat loss): eat 15–25% below maintenance. For 2,400 kcal maintenance, that\'s 1,800–2,040 kcal/day. The Calorie Deficit Calculator handles the math plus projects adaptive thermogenesis.
• Maintain: eat at maintenance. Use the 14-day calibration to find your real number; expect to recalibrate every 5–10 lbs of weight change.
• Bulk (muscle gain): eat 200–500 kcal above maintenance. For 2,400 kcal maintenance, that\'s 2,600–2,900 kcal/day. Lower end (200) for "lean bulk", upper end (500) for accelerated mass gain with more fat.

Try the calculators

• TDEE Calculator
• BMR Calculator (3 formulas compared)
• Maintenance Calorie Calculator
• Calorie Deficit Calculator
• Lean Body Mass (for Katch-McArdle BMR)

FAQ

Are TDEE and maintenance calories the same thing?

Yes. Total Daily Energy Expenditure is the scientific term; maintenance calories is the everyday term. Both refer to the total daily energy your body uses — BMR + thermic effect of food + exercise + NEAT — which equals the calorie intake that keeps weight stable over time. Different calculators may give slightly different numbers because they use different BMR formulas (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle) or different activity multipliers, but the underlying concept is identical. TDEE = maintenance calories. The two tools on this site (TDEE Calculator and Maintenance Calorie Calculator) use the same Mifflin-St Jeor BMR formula and the same activity multipliers — they're framed differently for different mental models but compute the same number.

Which BMR formula should I use — Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle?

For most adults: Mifflin-St Jeor. The 2005 systematic review by Frankenfield et al. (Journal of the American Dietetic Association) compared four BMR equations against indirect calorimetry in 47 studies and found Mifflin-St Jeor was the most accurate for non-obese adults. Harris-Benedict (1919, revised 1984) systematically overestimates BMR by 5%, particularly in older adults. Katch-McArdle uses lean body mass directly — making it more accurate than Mifflin-St Jeor for very lean or very heavy people, but it requires you to know your LBM, which most adults don't have a reliable measurement of. Practical rule: use Mifflin-St Jeor unless you have a DEXA-measured LBM, in which case use Katch-McArdle.

How accurate is "BMR × activity multiplier" as a maintenance calorie estimate?

Reasonably accurate for the population, noisy for individuals. The Mifflin-St Jeor BMR equation has a published prediction error of ±5%. The activity multiplier adds another ±10–15% error, mostly from NEAT (non-exercise activity thermogenesis — fidgeting, posture, spontaneous movement). James Levine's 1999 NEAT studies at Mayo Clinic showed NEAT alone can vary by 2,000 kcal/day between sedentary and active adults of the same height/weight. Two people described by their friends as "the same activity level" can have 400–600 kcal/day of real maintenance difference. This is why a calculator gives you a starting point, not a final answer — and why the 14-day eat-the-prediction calibration described in the Maintenance Calorie Calculator is the practical way to find your real number.