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BMR for Women: What Makes the Number Different

Standard BMR formulas already account for sex, but there’s more nuance for women specifically — from monthly hormonal shifts to pregnancy and menopause. Here’s what the formulas capture, and what they don’t.

🕑 6 min read 🔄 Updated 3 August 2026

Why the Formula Already Adjusts for Sex

The Mifflin-St Jeor equation for women subtracts 161 instead of adding 5, compared to the male version, reflecting that women on average carry a higher percentage of body fat and lower muscle mass at the same height and weight. This isn’t a value judgment about individual bodies — it’s a population-level average built into the math.

Mifflin-St Jeor, female

BMR (women)

BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(yrs) − 161

What the Formula Doesn’t Capture

1 The menstrual cycle

Resting energy expenditure can rise modestly — typically a small percentage — during the luteal phase (after ovulation, before menstruation) compared to the follicular phase, tied to progesterone’s thermogenic effect. It’s a real but minor fluctuation, not something formulas track day-to-day.

2 Pregnancy

BMR rises during pregnancy to support fetal growth and increased maternal tissue, particularly in the second and third trimesters. Standard formulas aren’t built for this — pregnant individuals should follow guidance from their doctor rather than a general calculator.

3 Menopause

The hormonal shifts around menopause are associated with changes in body composition, including a tendency toward reduced muscle mass and increased fat storage, which can lower BMR independent of age alone. Maintaining resistance training through this transition helps offset the effect.

4 Breastfeeding

Energy needs increase during breastfeeding to support milk production — another situation where individualized medical or dietitian guidance matters more than a general formula.

Muscle Mass Still Matters Most

The biggest controllable lever is the same for everyone: body composition. Women who strength train and maintain lean muscle mass tend to have a higher BMR than the population average for their stats, the same pattern seen in men. Resistance training is not just a "male" strategy — it’s the most effective tool available to anyone looking to support their metabolic rate.

Frequently Asked Questions

Slightly — resting energy expenditure tends to be modestly higher in the luteal phase (after ovulation) than the follicular phase, though the fluctuation is generally small.
Standard formulas don't account for pregnancy's increased energy needs. Pregnant individuals should follow guidance from their doctor rather than a general calculator.
The hormonal changes around menopause are linked to shifts in body composition that can lower BMR, though resistance training can help offset much of this effect.
The formula adjusts for average differences in body fat percentage and muscle mass between sexes at the same height and weight, based on population data.

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