BMR Calculator: What You Burn at Rest (Mifflin-St Jeor)
BMR (basal metabolic rate) is the calories your body burns at complete rest, typically 1,300–1,800 for women and 1,500–2,100 for men. This bmr calculator estimates yours with the Mifflin-St Jeor equation from your weight, height, age, and sex. Your BMR is the foundation: multiply it by your activity level to get TDEE, then set your calorie goal from there.
🧮 Calculate My BMR 🔥 Calorie Calculator
BMR Calculator
Your Basal Metabolic Rate — calories your body burns at complete rest. Mifflin-St Jeor equation.
Estimate only — not medical advice. BMR is the base; multiply by activity for TDEE.
What Is BMR?
Basal metabolic rate is the energy your body needs to keep you alive doing nothing, breathing, circulating blood, maintaining body temperature, running your brain. It accounts for roughly 60–70% of your total daily calorie burn, which is why every serious calorie plan starts here. The bmr calculator above gives you this number in seconds; understanding it helps you use it correctly.
BMR is closely related to resting metabolic rate (RMR), the terms are often used interchangeably. Technically, BMR is measured under strict lab conditions (fasted, fully rested, thermally neutral) while RMR is measured under slightly relaxed conditions and runs about 10% higher. For practical diet planning, the difference doesn’t matter.
How This BMR Calculator Works: Mifflin-St Jeor Explained
The calculator uses the Mifflin-St Jeor equation, the formula the Academy of Nutrition and Dietetics considers most accurate for the general population:
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
In plain English: heavier and taller people burn more at rest, BMR declines with age (about 1–2% per decade after 40, mostly from muscle loss), and men typically run higher because of greater muscle mass. No body-fat measurement needed, the equation works well for most adults.
BMR vs TDEE: Don’t Confuse Them
| BMR | TDEE | |
|---|---|---|
| What it measures | Calories at complete rest | Total calories burned all day |
| Typical size | 60–70% of daily burn | 100% |
| Use it for | The baseline of every calculation | Your actual calorie target |
| Relationship | BMR × activity multiplier | = TDEE |
Your bmr calculator result is not how much you should eat, it’s the floor your total is built on. A sedentary woman with a BMR of 1,400 still burns ~1,680/day total (× 1.2). Eating exactly at BMR with normal daily activity creates an accidental deficit, which is why “eat at your BMR” advice needs the activity context (see FAQ).
What Is a Normal BMR?
| Profile | Typical BMR range |
|---|---|
| Woman, 60kg, 165cm, 30y | ~1,330 |
| Woman, 75kg, 170cm, 40y | ~1,440 |
| Man, 80kg, 180cm, 30y | ~1,780 |
| Man, 95kg, 185cm, 40y | ~1,940 |
“Normal BMR for women” is one of the most-searched questions here: for an average adult woman it’s roughly 1,300–1,600. Below that usually means smaller stature or older age, not a “broken metabolism.” True metabolic outliers are rare; most “slow metabolism” stories are undercounted food intake, not low BMR.
How to Increase Your Metabolism (Honestly)
People searching how to increase metabolism usually want a shortcut; the honest answer is muscle, protein, sleep, and daily movement.
- Build muscle. Muscle burns ~6 cal/lb/day at rest vs ~2 for fat. Gaining 5 lbs of muscle adds roughly 20–30 calories to daily BMR, modest, but it compounds with the calories burned in training itself.
- Move more (NEAT). Non-exercise activity, walking, standing, fidgeting, varies by up to 800 calories a day between people. It’s the biggest “metabolism” lever you actually control.
- Eat enough protein. Protein’s thermic effect (20–30% of its calories burned in digestion) is triple that of fat or carbs.
- Don’t crash diet. Very low calories for weeks can suppress BMR by 10–15% (adaptive thermogenesis). Moderate deficits protect your metabolic rate.
- Sleep 7–9 hours. Poor sleep measurably reduces next-day energy expenditure and spikes hunger hormones.
Ignore metabolism “boosters” in pill or tea form, the effect sizes are trivial and the evidence is weak.
How BMR Changes Over a Lifetime
Your metabolic rate isn’t fixed, it follows a predictable curve. BMR is highest in infancy and childhood (growing bodies are expensive), stays fairly stable from your 20s to about 60, then declines slowly, roughly 0.7% per year after 60. But here’s the key finding from large NIH-analyzed datasets: most of that decline comes from losing muscle, not from aging itself. Adults who keep resistance training into their 50s and 60s maintain BMRs close to their younger selves.
Pregnancy raises BMR by roughly 10–20% in the later trimesters. Illness, fever, and recovery from surgery temporarily raise it too, the body spends energy healing. And during extended dieting, BMR can dip 10–15% below predicted (adaptive thermogenesis), which is why refeeds and diet breaks exist. The number moves, but almost always for explainable reasons, not mysterious ones.
Worked Example: Ana, 29, 65kg
Ana is 65kg, 168cm, 29 years old. Running Mifflin-St Jeor for her:
- BMR = (10 × 65) + (6.25 × 168) − (5 × 29) − 161 = 650 + 1,050 − 145 − 161 = 1,394
- She exercises 3x/week → TDEE = 1,394 × 1.55 = ~2,160
- Fat-loss target: 2,160 − 400 = ~1,760 calories/day
Notice her eating target (1,760) sits well above her BMR (1,394), that’s correct and sustainable. Our calorie calculator automates this whole chain.
Using Your BMR by Goal
For weight loss
Think of BMR as a reference point, not a floor. Eating below it for extended periods is not recommended without medical supervision. Set your deficit from TDEE (BMR × activity), not from BMR. A 300–500 calorie deficit from TDEE with high protein preserves both muscle and metabolic rate.
For weight gain
Knowing your BMR prevents the classic hard-gainer mistake: eating what “feels like a lot” while still landing near maintenance. Add 300–500 to TDEE, track for two weeks, and adjust. Calorie-dense whole foods (peanut butter, whole milk, rice, nuts) make the surplus comfortable.
For muscle building
A small surplus (+250–300 over TDEE) with progressive training builds muscle with minimal fat. Your BMR helps you sanity-check the numbers: if your calculated surplus target is barely above BMR, your activity multiplier is probably set too low.
Embed This BMR Calculator
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Frequently Asked Questions
What is a resting metabolic rate calculator?
A resting metabolic rate calculator estimates the calories your body burns at complete rest. It is the same thing as a BMR calculator, “resting metabolic rate” is just the lab-measured name for it.
Should I eat at my BMR to lose weight?
Not exactly, eat below your TDEE, not at your BMR. Your BMR is what you burn at rest; with normal daily activity you burn 20–50% more. Eating at BMR while living normally creates a bigger deficit than intended, which is hard to sustain.
My BMR is 1400, how much should I eat to lose weight?
Multiply by activity (×1.2 sedentary = 1,680 TDEE; ×1.55 moderate = 2,170), then subtract 300–500. So roughly 1,200–1,380 if sedentary, or 1,670–1,870 if moderately active. These are illustrative estimates only; adjust based on your actual progress over 2–3 weeks.
What is a normal BMR for a woman?
Roughly 1,300–1,600 for average adult women, varying with weight, height, and age. Lower usually reflects smaller stature, not a broken metabolism.
Does the BMR calculator work if I’m very muscular or obese?
It’s less accurate at extremes, Mifflin-St Jeor was validated on typical body compositions. Very muscular people can use the Katch-McArdle formula (needs body-fat %), which we’ll cover in a future guide.
Can I increase my BMR permanently?
Modestly, more muscle mass raises it slightly, and staying active keeps it from declining with age. The bigger wins are NEAT and training calories, which sit on top of BMR. Realistically, expect lifestyle changes to move your total daily burn by hundreds of calories, while BMR itself shifts by dozens.
Why is my friend’s BMR higher than mine at the same weight?
Age, height, sex, and muscle mass all shift the number. Two people at 70kg can differ by 200+ calories of BMR, a taller, younger, more muscular person burns noticeably more at rest than a shorter, older one at the same scale weight.
Sources
- NIH (PubMed): Mifflin-St Jeor validation studies; adaptive thermogenesis research.
- USDA Dietary Guidelines for Americans: energy balance framework.
- CDC: physical activity and healthy weight guidance.
- WHO: healthy diet and activity recommendations.
This article is for general information only and is not medical advice. Talk to a registered dietitian or your doctor about your personal nutrition needs.