BMR Calculator for Women
Women burn fewer calories at rest than men of the same weight and height — about 166 fewer a day, on average. The reason is body composition: women typically carry more essential fat and less muscle, and muscle is the tissue that burns energy around the clock. The BMR calculator for women above uses the female version of the Mifflin-St Jeor equation, which accounts for that difference, so your number is built for you rather than borrowed from a male average.
This page works through the formula for women, shows BMR at every age, explains how pregnancy, breastfeeding and the menstrual cycle change the number, and shows how to turn your BMR into a daily calorie target for weight loss, maintenance or gain.
The BMR Formula for Women
For women, the Mifflin-St Jeor equation is: BMR = 10 × weight in kg + 6.25 × height in cm − 5 × age in years − 161. The −161 at the end is what makes it the female formula — the male version adds 5 instead. Everything else is identical, which makes the 166-calorie gap easy to see: it is the difference between +5 and −161.
Worked Example: A 25-Year-Old Woman
A woman aged 25, weighing 60 kg, 165 cm tall. Step by step: 10 × 60 = 600; 6.25 × 165 = 1,031.25; 5 × 25 = 125, subtracted; then subtract 161. Total: 600 + 1,031.25 − 125 − 161 = 1,345.25, rounded to 1,345 calories a day. That is her resting burn — about 56 calories an hour, day and night, before she moves at all. Enter your own numbers in the BMR calculator above to get your figure.
Worked Example: A 40-Year-Old Woman
A woman aged 40, weighing 65 kg, 165 cm tall: 10 × 65 = 650; 6.25 × 165 = 1,031.25; 5 × 40 = 200, subtracted; minus 161. Total: 650 + 1,031.25 − 200 − 161 = 1,320.25, rounded to 1,320 calories a day. She is 5 kg heavier than the first example but 15 years older, and the two effects almost cancel out — her BMR is only 25 calories lower.
BMR for Women by Age
The table below shows BMR for women of average height (165 cm) at different ages and weights, all moderately active daily needs included so you can see the full picture.
| Age and weight | BMR | Daily needs (moderately active) |
|---|---|---|
| 25 years, 60 kg | 1,345 kcal | 2,085 kcal |
| 30 years, 62 kg | 1,340 kcal | 2,077 kcal |
| 40 years, 65 kg | 1,320 kcal | 2,046 kcal |
| 50 years, 68 kg | 1,300 kcal | 2,015 kcal |
| 60 years, 68 kg | 1,250 kcal | 1,938 kcal |
| 70 years, 65 kg | 1,170 kcal | 1,814 kcal |
Check the 50-year-old row: 10 × 68 + 6.25 × 165 − 5 × 50 − 161 = 680 + 1,031.25 − 250 − 161 = 1,300.25, rounded to 1,300, and 1,300 × 1.55 = 2,015 calories a day at moderate activity. The 30-year-old row checks out the same way: 620 + 1,031.25 − 150 − 161 = 1,340.25, rounded to 1,340, and 1,340 × 1.55 = 2,077. The calculator above does the same maths for your exact numbers.
How Pregnancy and Breastfeeding Change BMR
Pregnancy raises energy needs substantially, and BMR rises with it as the body supports the growing baby and the placenta. The extra cost is small in the first trimester — about 85 calories a day — then rises to roughly 285 a day in the second trimester and 475 a day in the third. Breastfeeding adds about 500 calories a day on top of maintenance, because producing milk is energy-intensive. If you are pregnant or breastfeeding, do not use a standard weight-loss target: use the pregnancy guidance from your doctor, and the pregnancy due date calculator to track your timeline.
| Stage | Extra calories a day | Notes |
|---|---|---|
| First trimester | About 85 kcal | Small rise; many women eat the same as before |
| Second trimester | About 285 kcal | Roughly one extra snack a day |
| Third trimester | About 475 kcal | Largest rise, as the baby grows fastest |
| Breastfeeding | About 500 kcal | On top of maintenance; stay hydrated |
Does the Menstrual Cycle Affect BMR?
Yes, slightly. BMR rises by roughly 100 to 300 calories a day in the luteal phase — the two weeks after ovulation — as progesterone increases body temperature and metabolic rate. Many women notice the effect as higher appetite and a small weight rise from water retention in the days before their period. The effect is real but modest, and it is not a reason to change your calorie target week by week. If you track your weight, compare the same phase of your cycle month to month rather than consecutive weeks.
From BMR to a Daily Target
Your BMR is the foundation. Multiply it by your activity factor to get your daily calorie needs, then adjust for your goal. For the 25-year-old woman in the worked example, BMR is 1,345; lightly active (× 1.375) gives 1,850 a day, and moderately active (× 1.55) gives 2,085. Her weight-loss target at a 500 deficit from light activity is 1,350 a day — safely above the 1,200 floor. The TDEE calculator shows every activity level at once, and the calorie calculator adds macro splits.
Why Women’s BMR Is Often Underestimated
- Using the male formula. The male version adds 166 calories a day. Always check the calculator uses the female constant (−161).
- Overestimating activity. Three gym sessions a week is moderately active at most. Choosing “very active” inflates the result by 300 calories or more.
- Forgetting muscle loss with age. A 55-year-old who has not strength-trained has less muscle than at 25, so the formula’s age term is doing real work — do not ignore it.
- Crash diets. Very low calorie intake can suppress BMR by 10 to 15 percent, which makes the formula overestimate your burn until you eat normally again.
- Thyroid problems. Underactive thyroid is more common in women and lowers BMR. Unexplained weight gain with fatigue is worth a blood test.
Strength Training and Women’s BMR
The most effective way for a woman to raise her BMR is to build muscle. Each kilogram of muscle burns about 13 calories a day at rest, and two strength sessions a week can add a kilogram or two of muscle in a few months — plus it protects the muscle you already have, which is what keeps BMR from falling with age. The fear that lifting weights makes women bulky is unfounded: women have far less testosterone than men, so strength training builds a firmer, stronger body, not a larger one. Combine it with 1.6 to 2.0 g of protein per kg of body weight a day for the best result.
Common Questions About Women’s BMR
Women often ask whether BMR changes with the contraceptive pill, with menopause, or with weight loss itself. The pill has a small effect at most. Menopause lowers BMR mainly through muscle loss and lower activity, not through hormones directly — which is why strength training matters even more after menopause. And weight loss lowers BMR because a lighter body costs less to run: losing 10 kg typically cuts BMR by about 100 calories a day, which is why targets need recalculating as you lose weight.
Related tools: your full daily burn from the TDEE calculator, a daily target with macros from the calorie calculator, and your weight category from the BMI calculator. The American College of Obstetricians and Gynecologists has guidance on nutrition and energy needs in pregnancy.
Quick Reference
Keep the reference figures below handy while you plan.
| Person | BMR (Mifflin-St Jeor) | Daily needs (moderate) |
|---|---|---|
| Man, 30, 70 kg, 175 cm | 1,649 kcal | 2,556 kcal |
| Woman, 25, 60 kg, 165 cm | 1,345 kcal | 2,085 kcal |
| Man, 40, 80 kg, 178 cm | 1,718 kcal | 2,662 kcal |
| Woman, 40, 65 kg, 165 cm | 1,320 kcal | 2,046 kcal |
What to remember
- BMR is the calories you burn at complete rest — 60 to 70 percent of your daily total.
- Men burn about 166 calories a day more than women at the same size, through higher muscle mass.
- BMR falls about 5 calories a year, mostly through muscle loss.
- Mifflin-St Jeor is the most accurate formula for most adults; Katch-McArdle is best for very lean or muscular people.
- Multiply BMR by an activity factor (1.2 to 1.9) to get your daily calorie needs.
Your checklist
- Enter your sex, age, weight and height in the calculator above.
- Read your BMR and compare the three formulas.
- Multiply by your activity level to get your daily needs.
- Set your goal target: minus 500 for weight loss, plus 500 for gain.
- Recalculate whenever your weight changes by 5 kg or more.
Mistakes to avoid
- Using pounds instead of kilograms — divide pounds by 2.205 first.
- Using the wrong constant: men add 5, women subtract 161.
- Treating BMR as daily needs — eating only your BMR is a large deficit.
- Forgetting the age term, which adds up to 150 calories between age 25 and 55.
- Crash dieting, which can suppress BMR by 10 to 15 percent.
Frequently Asked Questions
What is a normal BMR for a woman?
Most adult women have a BMR between 1,200 and 1,600 calories a day. A 25-year-old at 60 kg and 165 cm has a BMR of about 1,345; a taller or heavier woman will be higher, a smaller or older woman lower. Activity is added on top to get daily needs.
How do I calculate BMR for a woman?
Use the female Mifflin-St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age − 161. For a 25-year-old at 60 kg and 165 cm: 600 + 1,031.25 − 125 − 161 = 1,345 calories a day.
Does BMR change during pregnancy?
Yes. Energy needs rise by about 85 calories a day in the first trimester, 285 in the second and 475 in the third. Breastfeeding adds about 500 calories a day. Do not diet during pregnancy without medical guidance.
Why is my BMR lower than my husband’s?
Mainly muscle mass and size. Men average more muscle at the same weight, and muscle burns more energy at rest. At identical weight, height and age, the male formula gives a BMR about 166 calories higher than the female one.
Does menopause lower BMR?
Menopause itself has a modest direct effect, but muscle loss and reduced activity around menopause lower BMR noticeably. Strength training twice a week and enough protein are the best defences.
How many calories should a woman eat a day?
It depends on BMR and activity. A moderately active 25-year-old woman at 60 kg needs about 2,085 calories a day to maintain her weight; a sedentary 55-year-old at 65 kg needs about 1,970. Use the calculator above for your own number, then subtract 500 for weight loss.
Disclaimer: This calculator provides estimates for general information only and is not medical advice. BMR equations are population averages and can be off by 10 percent or more for individuals. Consult a doctor or registered dietitian before using BMR to plan a diet, especially during pregnancy, breastfeeding, or if you have a thyroid condition.