BMR vs RMR — what’s the difference?

RMR (Resting Metabolic Rate) is BMR measured under slightly less strict conditions. They differ by a few percent and are often used interchangeably outside of clinical studies.

Should I eat at my BMR?

No — BMR is the absolute floor. Eat at your TDEE to maintain weight, or create a moderate deficit/surplus relative to TDEE for fat loss or muscle gain.

Why is my BMR lower than my fitness tracker says?

Trackers use different equations (often Harris–Benedict or proprietary) and may overestimate by 5–10%. Mifflin–St Jeor tends to be more accurate for the general population.

Does muscle mass change my BMR?

Yes. Muscle is metabolically more active than fat, so individuals with more lean mass will have a higher BMR than the equation alone predicts.

Is BMR static through life?

No — BMR typically declines about 1–2% per decade after age 20, largely due to muscle loss. Strength training and protein intake meaningfully slow that decline.

Nutrition · Energy expenditure

BMR Calculator

Discover the calories your body burns at complete rest.

Your details

Sex

Age

years

Height

Weight

Mifflin–St Jeor is the gold standard for adults aged 19+. Not designed for pregnancy or for children under 19.

Basal metabolic rate

1598kcal/day

Calories your body burns at complete rest, just keeping the lights on.

Estimated daily burn by activity

Sedentary

×1.2 · Little or no exercise

1,918kcal

Lightly active

×1.375 · 1–3 days/week light exercise

2,197kcal

Moderately active

×1.55 · 3–5 days/week moderate

2,477kcal

Very active

×1.725 · 6–7 days/week hard exercise

2,757kcal

Athlete

×1.9 · Twice-daily training

3,036kcal

What is BMR?

Your Basal Metabolic Rate (BMR) is the number of calories your body burns just to keep you alive — beating your heart, breathing, regulating temperature, and maintaining cellular function — while you’re at complete rest.

It is the foundation of every daily calorie estimate. Multiply it by an activity factor and you get your Total Daily Energy Expenditure (TDEE).

How BMR is calculated

Elements84 uses the Mifflin–St Jeor equation, considered the most accurate for general adults:

Men:    BMR = 10·weight(kg) + 6.25·height(cm) − 5·age + 5
Women:  BMR = 10·weight(kg) + 6.25·height(cm) − 5·age − 161

Turning BMR into daily calories

Multiply your BMR by an activity factor — sedentary 1.2, lightly active 1.375, moderately active 1.55, very active 1.725, athlete 1.9 — to estimate your full daily calorie burn (TDEE).

Category reference

Category	Range	What it means
Sedentary	× 1.2	Little or no exercise
Lightly active	× 1.375	1–3 days/week light exercise
Moderately active	× 1.55	3–5 days/week moderate
Very active	× 1.725	6–7 days/week hard exercise
Athlete	× 1.9	Twice-daily training

Limitations & caveats

BMR is an estimate — actual rates vary with muscle mass, hormones and genetics.
Mifflin–St Jeor is designed for adults aged 19–80.
Pregnancy, lactation and certain medical conditions can shift BMR meaningfully.
Trackers and smart-scale BMR figures often differ by ±10% — use any one source consistently.
BMR doesn’t include the calories used to digest food (TEF) or daily activity (NEAT).
Combine BMR with body-fat % and activity tracking for a fuller energy picture.