RMR Calculator: Resting Metabolic Rate
Enter your sex, age, height and weight to find out how many calories your body burns at rest each day. This calculator uses the Mifflin-St Jeor equation, the most widely validated formula for the general population, and also offers the revised Harris-Benedict and Katch-McArdle methods. Switch between metric and imperial units, pick your daily activity level to see your Total Daily Energy Expenditure (TDEE), and use the calorie-goal panel to find out how large a deficit or surplus you need.
What is resting metabolic rate (RMR)?
Resting Metabolic Rate is the number of calories your body burns each day to keep essential organs working while you are at rest but not fully asleep. It covers breathing, circulating blood, maintaining body temperature and running cellular repair. RMR is slightly higher than the more restrictive Basal Metabolic Rate (BMR), because RMR is measured after minimal physical movement rather than requiring a full overnight fast and complete stillness. In practice the two terms are often used interchangeably, and the difference is typically under 5%. For most adults, RMR accounts for 60 to 75% of all calories burned each day.
Which formula does this calculator use?
The default is the Mifflin-St Jeor equation, developed in 1990 and endorsed by the Academy of Nutrition and Dietetics as the most accurate predictive equation for most adults. It uses weight, height, age and sex: for men, RMR = 10W + 6.25H - 5A + 5; for women, RMR = 10W + 6.25H - 5A - 161 (where W is in kg, H in cm, and A in years). The revised Harris-Benedict equation (Pavlidou, 2023) is also available and showed an R-squared of 0.95 for men and 0.86 for women in validation studies. The Katch-McArdle formula works from lean body mass rather than total weight, making it the best choice for lean or athletic individuals: RMR = 370 + 21.6 x lean mass (kg).
How to calculate your TDEE from RMR
Total Daily Energy Expenditure (TDEE) is RMR multiplied by a Physical Activity Level (PAL) factor. Sedentary people (desk job, little movement) use 1.2; lightly active (1-3 sessions of exercise per week) use 1.375; moderately active (3-5 sessions) use 1.55; very active (6-7 hard sessions) use 1.725; and extremely active (physical job plus daily intense training) use 1.9. To lose weight, eat below your TDEE; to gain, eat above it. A deficit of 500 kcal/day is a common starting point for roughly 0.5 kg (1 lb) weight loss per week, because approximately 7,700 kcal corresponds to one kilogram of body fat.
What affects your RMR?
Lean body mass is the single biggest controllable driver: each kilogram of muscle burns roughly 13 kcal/day at rest, far more than the same mass of fat. RMR naturally falls by about 2% per decade as muscle mass declines, which is why maintaining resistance training through middle age and beyond makes such a difference. Sleep debt, severe calorie restriction (the so-called adaptive thermogenesis), and very low thyroid function all reduce RMR. Stimulants such as caffeine and capsaicin raise it by a few percent temporarily. Genetics explain the remaining variance that formulas cannot capture, which is why two people with identical measurements can have RMRs that differ by hundreds of calories.
RMR ranges by sex and activity level
| Activity level | PAL multiplier | Typical male TDEE | Typical female TDEE |
|---|---|---|---|
| Sedentary | 1.20 | 1,941 kcal | 1,742 kcal |
| Lightly active | 1.375 | 2,224 kcal | 1,996 kcal |
| Moderately active | 1.55 | 2,507 kcal | 2,250 kcal |
| Very active | 1.725 | 2,790 kcal | 2,504 kcal |
| Extremely active | 1.90 | 3,073 kcal | 2,758 kcal |
Mifflin-St Jeor values for a 30-year-old at 70 kg (154 lb) and 170 cm (67 in): RMR 1,618 kcal/day for men and 1,452 kcal/day for women, multiplied by each PAL factor. Individual results vary with age, body composition and formula chosen.
Frequently asked questions
What is the difference between RMR and BMR?
Basal Metabolic Rate (BMR) is measured under strict conditions: fasting overnight, lying still in a temperature-controlled room and in a post-absorptive state. Resting Metabolic Rate (RMR) allows for minimal movement and a shorter fasting period, making it easier to measure in practice. The two values are usually within 5% of each other. Most online calculators labelled "BMR" actually calculate RMR using predictive equations rather than true basal conditions.
How accurate are RMR prediction equations?
The best equations predict measured RMR to within 10% for about 60-70% of individuals. Online calculators using these equations have typical accuracy of plus or minus 200 to 300 kcal/day compared to metabolic testing. Accuracy is lowest for the very obese, very muscular and very elderly. For clinical purposes, indirect calorimetry (measuring exhaled gases) is the gold standard and is accurate to within 1-2%.
Which RMR formula should I use?
Mifflin-St Jeor is the recommended default for most adults. Use Katch-McArdle if you know your body-fat percentage and are particularly lean or athletic, because it works from lean mass rather than total weight and avoids the formula overestimating metabolic rate for people carrying extra fat. The revised Harris-Benedict (2023) is useful for comparison and tends to perform slightly better for older adults.
Can I raise my RMR?
Yes, primarily by building muscle. Each kilogram of lean mass adds roughly 13 kcal/day to your RMR. Resistance training two to four times per week is the most effective long-term strategy. Avoiding severe calorie restriction helps prevent adaptive thermogenesis, where the body lowers its metabolic rate to conserve energy. Adequate sleep, sufficient protein intake and staying hydrated also support a healthy metabolism.
What is TDEE and how does it relate to RMR?
Total Daily Energy Expenditure (TDEE) is your RMR multiplied by a Physical Activity Level (PAL) factor that accounts for exercise, incidental movement and the thermic effect of food (roughly 10% of calories). TDEE is the number you compare against your food intake to determine whether you are in a calorie deficit, maintenance or surplus. Eating at or near TDEE maintains weight; eating below it leads to weight loss over time.
How many calories do I need to lose 1 kg per week?
One kilogram of body fat stores roughly 7,700 kcal. To lose 1 kg per week you would need a daily deficit of about 1,100 kcal (7,700 divided by 7 days). That is aggressive for most people and risks muscle loss alongside fat. A more sustainable target is 0.5 kg per week, requiring a 500-550 kcal daily deficit. This calculator shows the deficit relative to your TDEE when you enter a calorie goal.
Sources
- Mifflin MD et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition.
- Pavlidou E et al. (2023). Revised Harris-Benedict Equation: New Human Resting Metabolic Rate Equation. Nutrients. PMC9967803.
- Cunningham JJ (1991). Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation (REE = 370 + 21.6 x fat-free mass) - the equation popularised as Katch-McArdle. American Journal of Clinical Nutrition 54:963-969.