Type the same height, weight and age into any BMR calculator, switch "male" to "female", and the number drops by about 160 to 170 calories a day. Many people read that as "women have a slower metabolism." The research tells a more useful story: most of the gap comes from body composition, not from sex itself, and the part that is left over is small.
This guide explains how much higher BMR is in men on average, why the formulas treat women and men differently, what happens when you compare people with the same lean mass, and how women and men should actually use their number when planning calories.
The short answer
- On average, men have a higher BMR than women, mainly because they are larger and carry more lean mass (muscle, organs, bone).
- In a classic study of 522 adults, measured resting metabolic rate was 23% higher in men (about 1,740 kcal/day) than in women (about 1,348 kcal/day).
- After adjusting for fat-free mass, fat mass and fitness, the gap shrank to about 3% (roughly 50 kcal/day).
- Same-stats formulas exaggerate the difference for women who are muscular and understate it for men with low muscle mass.
How much higher is BMR in men than in women?
Large studies give a consistent picture. In the study by Arciero, Goran and Poehlman, published in the Journal of Applied Physiology (1993), 328 men and 194 women aged 17 to 81 had their resting metabolic rate measured. The men averaged about 1,740 kcal/day and the women about 1,348 kcal/day, a 23% difference.
Population averages hide a wide spread. An analysis of BMR data by MacroFactor notes that roughly 1 in 5 women has a BMR below 1,200 kcal/day and roughly 1 in 5 men has one above 2,200 kcal/day. Plenty of women burn more at rest than plenty of men. If you want to see typical values for your age group, see our average BMR by age chart.
Why the formulas treat women and men differently
Most calculators use the Mifflin-St Jeor equation:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Everything is identical except the last term. That constant, a 166-calorie gap, is not a biological law. It is a statistical shortcut. The equation does not know your body composition, so it uses sex as a stand-in for "on average, this person probably has more or less lean mass at this weight." The revised Harris-Benedict equation does the same thing with different coefficients. Our article on all five BMR equations covers each one in detail.
Same body, different number: a worked example
Take two people who are both 35 years old, 170 cm tall and 70 kg.
| Equation | Man | Woman | Gap |
|---|---|---|---|
| Mifflin-St Jeor | 1,593 kcal | 1,427 kcal | 166 kcal |
| Revised Harris-Benedict | 1,643 kcal | 1,470 kcal | 173 kcal |
| Katch-McArdle (man 18% body fat, woman 30% body fat) | 1,610 kcal | 1,428 kcal | 182 kcal |
| Katch-McArdle (both 25% body fat) | 1,504 kcal | 1,504 kcal | 0 kcal |
The last row is the key insight. The Katch-McArdle formula uses lean body mass instead of sex. When two people have the same lean mass, it predicts the same BMR. If you know your body-fat percentage, our guide to the Katch-McArdle formula shows how to use it.
What explains the gap? Body composition first
Lean mass does most of the work
Fat-free mass, which includes muscle, organs, bone and water, is the strongest single predictor of BMR. Men on average are taller, heavier and carry a higher share of muscle, partly because of higher testosterone levels, as the Cleveland Clinic notes. Women on average carry a higher share of body fat, which is metabolically less active per kilogram.
A study from the Mayo Clinic (Owen, 1988) found that when resting metabolic rate was plotted against fat-free mass, the regression lines for men and women were indistinguishable, and one equation could serve both sexes. A later study in the British Journal of Nutrition (2001) also found that the male-female gap became non-significant once resting metabolic rate was adjusted for lean body mass.
A small residual difference may remain
Not every study agrees that the gap disappears completely. Arciero and colleagues found a 3% lower adjusted RMR in women, and a respiratory-chamber study by Ferraro et al. (1992) found 24-hour energy expenditure about 124 kcal/day higher in men after adjusting for fat-free mass, fat mass and age. A 2025 review in Physiological Reviews summarises the evidence as women having slightly lower BMR even after these adjustments, while finding no evidence that the thermic effect of food differs by sex.
The honest summary: after body composition is accounted for, any remaining sex difference is in the range of zero to about 100 calories a day. That is smaller than the normal day-to-day measurement error of most BMR tests.
Organ size and muscle distribution
Part of the remaining gap may come from what makes up the lean mass. Organs such as the heart, liver, kidneys and brain burn far more energy per kilogram than resting muscle. Differences in organ size and in how lean mass is distributed may explain why "lean mass" alone does not perfectly line up between groups. The research here is still developing, so treat it as a likely contributor rather than a proven cause.
Factors that affect women's BMR specifically
The menstrual cycle
Resting metabolism tends to be slightly higher in the luteal phase (the roughly two weeks after ovulation). A 2020 meta-analysis in PLOS One of 26 studies found a small but significant increase. A 2026 systematic review in Frontiers in Physiology estimated the rise at roughly 30 to 120 kcal/day (about 3 to 5%) and noted that it can overlap with normal daily variability. It is real, but too small to justify planning a separate diet for each half of your cycle.
Pregnancy, breastfeeding and menopause
Pregnancy and breastfeeding raise energy needs, and menopause is often linked with changes in body composition. These are big topics in their own right and need individual advice from a doctor or registered dietitian. A standard BMR calculator is not designed for pregnancy.
Factors that affect men's BMR specifically
Men's higher average BMR depends heavily on keeping their muscle. Lean mass tends to decline with age, inactivity and long periods of under-eating, and BMR tends to follow it down. The good news is that resistance training helps preserve lean mass in both sexes, though the calorie effect per kilogram of muscle is smaller than fitness myths suggest. See does muscle really burn 50 calories a day for the real numbers.
How BMR changes with age in women and men
In the Mifflin-St Jeor formula, both sexes lose 5 kcal per year of age, so the gap between them stays fixed at 166 kcal. Using our 170 cm, 70 kg example:
| Age | Man (Mifflin-St Jeor) | Woman (Mifflin-St Jeor) |
|---|---|---|
| 25 | 1,643 kcal | 1,477 kcal |
| 45 | 1,543 kcal | 1,377 kcal |
| 65 | 1,443 kcal | 1,277 kcal |
In real life, the age-related drop is driven mostly by loss of lean mass and lower activity. Staying active and strong helps slow it for everyone.
What this means for your calorie target
Here is how to use these findings in practice:
- Start with a standard calculator. Mifflin-St Jeor is accurate to within about 10% for most adults, which is fine as a starting point.
- Use Katch-McArdle if you know your body fat. If you are a muscular woman, the standard formula may underestimate your BMR. If you are a man with low muscle mass, it may overestimate it.
- Multiply by an activity factor to estimate your total daily energy expenditure (TDEE). Total energy needs, not BMR, set your eating target.
- Track your weight trend for 2 to 3 weeks and adjust. Your real-world results beat any equation.
Because women's BMR is often lower in absolute terms, a fixed calorie deficit takes a bigger bite out of their energy intake. A 500-calorie deficit is about 24% of a 2,075-calorie TDEE (a 65 kg, 164 cm, 35-year-old woman at moderate activity) but only about 18% of a 2,778-calorie TDEE (an 85 kg, 178 cm, 35-year-old man at the same activity). That is why percentage-based deficits are often easier to sustain. Read how many calories to eat to lose weight for the full method.
A word on very low calorie diets
Generic advice such as "eat 1,200 calories" can sit close to or even below the BMR of many women and is well below most men's needs. Long periods of very low intake can make it harder to keep muscle and meet nutrient needs. If you are considering a very low calorie plan, talk to a doctor or registered dietitian first.
Common myths about women's and men's metabolism
- "Women's metabolism is broken compared with men's." No. Per kilogram of lean mass, the difference is small. A study of healthy young adults found BMR per kilogram of body weight was not significantly different between the sexes (mechanistic BMR model study, 2014).
- "Men burn more calories digesting food." The evidence does not show a meaningful sex difference in the thermic effect of food.
- "The 166-calorie gap applies to everyone." It is an average correction, not your personal number.
Frequently asked questions
Why do men have a higher BMR than women?
Mostly because men on average are larger and carry more lean mass, which uses more energy at rest. When studies adjust for body composition, the gap shrinks to a few percent or disappears.
What is a normal BMR for a woman?
Many adult women fall roughly between 1,200 and 1,500 kcal/day, but the healthy range is wide. Height, weight, age and muscle mass all move the number, so calculate your own rather than relying on an average.
What is a normal BMR for a man?
Many adult men fall roughly between 1,500 and 1,900 kcal/day, with taller and more muscular men higher. As with women, the range is broad.
Is the BMR calculator less accurate for women?
Validation studies have found prediction equations sometimes agree less well with measured BMR in women than in men. Using lean mass (Katch-McArdle) and tracking your real weight trend can improve accuracy.
Does the menstrual cycle change BMR?
Slightly. Research suggests resting metabolic rate may rise by roughly 30 to 120 kcal/day in the luteal phase. The effect is small and varies between women.
If a woman and a man have the same muscle mass, is their BMR the same?
Very close. Studies show most of the difference disappears when lean mass is matched, with at most a small residual gap of about 3% in some research.
Should women eat less than men to lose weight?
Calorie targets should be based on your own BMR and activity, not on sex alone. A smaller person, of any sex, needs fewer calories. Percentage-based deficits help keep the target fair for different body sizes.
This article is for general education and is not medical advice. If you are pregnant, breastfeeding, have a medical condition or a history of disordered eating, speak with a qualified health professional before changing your diet.
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