BMR Calculator

What Is BMR, and Why Does It Matter?

Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest — just keeping your heart beating, your lungs breathing, and your organs running. It's the floor of your daily energy burn, before you factor in walking, working out, or even digesting food.

If you've ever wondered why two people of the same weight can eat very differently, BMR is a big part of the answer. Muscle is more metabolically active than fat, so someone with more lean mass burns more calories at rest. Age matters too — BMR drops roughly 1-2% per decade after your 20s, which is why "eating like you used to" slowly stops working.

How This Calculator Works

This calculator runs your numbers through three well-known formulas and takes the median, which smooths out each formula's individual bias:

• Mifflin-St Jeor — the most widely used clinical formula, and the one most dietitians reach for.
• Harris-Benedict (revised) — an older standard that still holds up well for most adults.
• Cunningham — uses body fat percentage, so it's more accurate for lean or athletic people.

If you enter your body fat percentage, the Cunningham estimate gets weighted more heavily. Leave it blank and the calculator auto-estimates from your age and gender.

What Your Number Actually Means

Take your BMR and multiply it by an activity factor to get your TDEE (total daily energy expenditure) — the number you actually need to maintain your weight:

• Sedentary (desk job, little exercise): BMR × 1.2
• Lightly active (1-3 workouts/week): BMR × 1.375
• Moderately active (3-5 workouts/week): BMR × 1.55
• Very active (6-7 workouts/week): BMR × 1.725

To lose weight, eat below your TDEE — a 500-calorie daily deficit equals roughly one pound per week. To gain muscle, eat slightly above it and train. But never eat below your BMR for long: that's the energy your body needs just to function, and going under it chronically slows your metabolism down.

BMR vs. TDEE: Don't Confuse Them

BMR is your resting burn; TDEE is BMR plus everything you do on top of it. Most people use BMR as a reference point and TDEE as their actual daily target. If a calorie calculator gives you one number, it's usually TDEE, not BMR — that's why this page shows both.

FAQ

Is BMR the same as metabolism?

BMR is the biggest single piece of your metabolism, but not the whole thing. Your total metabolism also includes the thermic effect of food (digestion burns ~10% of calories) and all your activity. BMR is just the resting baseline.

Can I raise my BMR?

Yes, mainly by building muscle. Each pound of muscle burns roughly 6 calories per day at rest, so adding 10 pounds of lean mass raises your BMR by about 60 calories daily. That sounds small, but it compounds over months.

Why does my BMR drop with age?

Mostly because people lose muscle as they get older, and partly because of hormonal changes. The fix is the same at any age: resistance training to hold onto lean mass, plus enough protein.