BMR Calculator for Women — Female Metabolic Rate

The female version of Mifflin-St Jeor is the same equation with − 161 on the end instead of

• 5. Nothing else about the calculation changes. Enter age, weight and height:

The female formula, worked out

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

The equation is metric, so convert first. A 35-year-old woman at 150 lb and 5 ft 5 in: 150 ÷ 2.205 = 68.0 kg, and 65 in × 2.54 = 165.1 cm.

10 × 68 + 6.25 × 165 − 5 × 35 − 161 = 680 + 1,031 − 175 − 161 = 1,375 kcal/day

A smaller frame — 125 lb at 5 ft 2 in, same age, which is 56.7 kg and 157.5 cm — gives 567 + 984 − 175 − 161 = 1,215 kcal/day. The pounds to kg and kg to pounds converters handle that first step if you would rather not do it in your head.

Where the − 161 comes from

It is not a statement that female metabolism is inherently slower. In the regression as published, sex appears once as a single 166 kcal term, and the paired constants everyone quotes are just that one term rewritten. What it stands in for is a difference in body composition: at the same recorded weight, the women in the fitting sample carried less fat-free mass than the men.

The 2023 Dietary Reference Intakes make the point directly — once body composition is controlled for, sex has minimal effect on resting metabolic rate. A woman with substantial lean mass can sit above a man of the same weight, and the equation will still hand her the lower number, because it cannot see the thing that decides.

That is the honest limitation to carry away from this page. Fat-free mass explains 60 to 80% of the differences in resting expenditure between people; weight on its own explains about half. BMI vs body fat percentage is a useful companion here.

Cycle, menopause and what actually moves

Three questions come up constantly, and they deserve different-sized answers.

The menstrual cycle. Basal rate fluctuates a little across the month, running slightly higher in the luteal phase. It is not a planning variable — the fluid-driven swing on the scale in the same week is larger and more noticeable than the metabolic change underneath it.

Menopause. The change is real, but the mechanism is not the one people assume. Size-adjusted energy expenditure holds steady from roughly 20 to 60 years of age. What shifts around the transition is body composition: lean mass falls, and the resting floor follows. That reframes the response — the intervention is resistance training and adequate protein, aimed at the tissue rather than at “the metabolism.”

Breastfeeding. Milk production costs energy, and no standard BMR equation accounts for it. Basal formulas describe a non-lactating body. If you are nursing, the number above is your baseline and the additional requirement is a conversation with your clinician, since it depends on how much of the baby’s intake is breast milk and how quickly you intend to return to pre-pregnancy weight. For the pregnancy side of the same question, see BMR during pregnancy.

Using it to lose weight without under-eating

The single most common mistake made with this page is eating 1,375 kcal because that is what it said. The basal figure is what a body costs at complete rest — it contains no walking, no work, no training. Eating at it produces a much steeper deficit than intended, and steep deficits are what trigger the adaptive slowdown described on the slow metabolism test page.

The order that works: basal figure → multiply by activity factor → subtract a moderate deficit from that total → let three to four weeks of weight data tell you whether the estimate was right for you. The BMR vs TDEE page walks through the multiplication, and the main BMR calculator covers how accurate the starting estimate can be expected to be.

This content is informational and does not replace evaluation by a physician or registered dietitian.