BMR and Daily Calorie Needs
How many calories you need depends on two things: the energy your body uses at rest and how active you are. Several equations estimate the first, and official dietary standards multiply it by an activity factor. This guide compares the methods and shows why their results differ.
Basal Metabolic Rate and Activity
Basal metabolic rate (BMR) is the energy your body uses at complete rest to breathe, circulate blood and keep its temperature. Daily energy needs are BMR multiplied by a physical activity level (PAL), the ratio of total energy use to BMR. The FAO/WHO/UNU report on human energy requirements groups lifestyles into three PAL ranges:
| Lifestyle | PAL range | Example in the report |
|---|---|---|
| Sedentary or light activity | 1.40–1.69 | 1.53 |
| Active or moderately active | 1.70–1.99 | 1.76 |
| Vigorous or vigorously active | 2.00–2.40 | 2.25 |
The Equations
| Method | Men | Women |
|---|---|---|
| Mifflin-St Jeor (1990) | 10W + 6.25H − 5A + 5 | 10W + 6.25H − 5A − 161 |
| Harris-Benedict | 66.473 + 13.7516W + 5.0033H − 6.755A | 655.0955 + 9.5634W + 1.8496H − 4.6756A |
| FAO/WHO/UNU (Schofield), 30–59 years | 11.472W + 873.1 | 8.126W + 845.6 |
W is weight in kg, H height in cm and A age in years. Mifflin-St Jeor comes from a 1990 study of 498 healthy adults aged 19 to 78; its abstract notes that the original Harris-Benedict equations overestimated measured resting energy by about 5%. The FAO/WHO/UNU report uses weight-only equations with separate bands for ages 18–29, 30–59 and 60 and over.
Japan's Dietary Reference Intakes 2025
Japan's Ministry of Health, Labour and Welfare estimates BMR as a reference value per kilogram times body weight, with values by sex and age: for example 23.7 kcal/kg for men aged 18–29 and 21.9 kcal/kg for women aged 30–49. Daily needs are BMR × 1.50, 1.75 or 2.00 for low, moderate and high activity up to age 64, with lower levels at older ages. The report notes that the per-kilogram value needs care for people far from the reference weight of their age group, and also lists the National Institute of Health and Nutrition equation, checked for Japanese adults aged 18 to 79.
Korea's Dietary Reference Intakes 2025
Korea's 2025 standard, published by the Ministry of Health and Welfare, keeps the US/Canada equations it has used since 2005 and calculates the estimated energy requirement directly:
- Men: 662 − 9.53 × age + PA × (15.91 × weight + 539.6 × height in m)
- Women: 354 − 6.91 × age + PA × (9.36 × weight + 726 × height in m)
PA is a coefficient for four activity levels: 1.0, 1.11, 1.25 and 1.48 for men, and 1.0, 1.12, 1.27 and 1.45 for women. The published tables use the "low active" level and round down to 100 kcal.
One Person, Six Results
For a woman aged 35, 165 cm and 60 kg:
| Method | BMR (kcal) | Daily needs, light to moderate activity |
|---|---|---|
| Mifflin-St Jeor | 1,295 | 1,982 (PAL 1.53) |
| Harris-Benedict | 1,370 | 2,097 (PAL 1.53) |
| FAO/WHO/UNU | 1,333 | 2,040 (PAL 1.53) |
| Japan DRI 2025 | 1,314 | 2,300 (PAL 1.75, "moderate") |
| Japan NIHN equation | 1,265 | 2,213 (PAL 1.75) |
| Korea KDRIs 2025 | – | 2,083 ("low active") |
The spread of a few hundred kilocalories is normal: each method comes from different people and inputs. Treat any result as a starting point and adjust it to how your weight actually changes over a few weeks.
Frequently Asked Questions
What is the difference between BMR and TDEE?
BMR is energy at rest. TDEE, total daily energy expenditure, adds everything you do in a day; it is BMR times your physical activity level.
Which equation is most accurate?
None is exact for an individual. Mifflin-St Jeor is widely used for adults; Japan's and Korea's standards are the basis of official tables in those countries. Expect individual needs to differ by 10% or more.
Can I use these numbers to lose weight?
They estimate the energy needed to keep your current weight. Talk to a doctor or dietitian before cutting calories, especially with a health condition.
Sources
Source: Mifflin et al., Am J Clin Nutr 1990;51:241-7 (PubMed); FAO/WHO/UNU: Human energy requirements (2004), table 5.1 · Last checked:
Source: FAO/WHO/UNU: Human energy requirements (2004), tables 5.1-5.3 · Last checked:
Source: 厚生労働省「日本人の食事摂取基準（2025年版）」策定検討会報告書 エネルギー（表3・表4） · Last checked:
Source: 보건복지부: 2025 한국인 영양소 섭취기준 1권 에너지와 다량영양소 (표 1, 표 7) · Last checked: