Free rmr calculator
See how many calories your body burns at rest. Enter your height, weight, age, and sex and the RMR calculator returns your resting metabolic rate using the Mifflin-St Jeor equation, an optional body-fat-based Katch-McArdle estimate, and your daily calorie needs at every activity level — updated live, as you type.
On this page17 sections
| Activity | × | Calories / day |
|---|---|---|
| Sedentary · little or no exercise | 1.2 | 2,039 cal/day |
| Lightly active · 1–3 days/week | 1.375 | 2,336 cal/day |
| Moderately active · 3–5 days/week | 1.55 | 2,633 cal/day |
| Very active · 6–7 days/week | 1.725 | 2,930 cal/day |
| Athlete · twice daily / physical job | 1.9 | 3,228 cal/day |
RMR is an estimate; individual metabolism varies. How accurate is this?
Results are estimates. Consult a professional.
What is resting metabolic rate (RMR)?
Your resting metabolic rate is the number of calories your body burns to keep you alive while at rest — breathing, circulating blood, regulating temperature, repairing cells, and running your brain and organs. It is the single largest slice of your daily energy use, accounting for roughly 60–70% of the calories most people spend in a day, before any deliberate activity. This RMR calculator estimates that resting burn from four inputs: your sex, age, height, and weight.
RMR is the practical, real-world measure of your metabolism at rest. It is the figure fitness centres, dietitians, and doctors reach for most often, because — unlike its stricter cousin, basal metabolic rate (BMR) — it can be measured without an overnight stay and a 12-hour fast. For everyday calorie planning, your RMR is the foundation: the floor you build your daily calorie target on top of.
How the RMR calculator works
The calculator uses the Mifflin-St Jeor equation, the predictive formula clinicians and dietitians favour. It is the same equation used to estimate BMR — and that is deliberate: the common predictive equations do not encode the small lab gap between measured RMR and BMR, so a predicted RMR is the Mifflin-St Jeor value.
What the number means
The result is your maintenance baseline at zero activity — the calories you would burn if you spent the entire day resting. It is not how much you should eat, because almost nobody lies still for 24 hours. Standing, walking, working, and exercising all add to it. Think of RMR as the foundation, and your real daily calorie need as that foundation plus everything you do on top of it.
RMR vs BMR: what's the difference?
RMR and BMR both measure your resting calorie burn, and in everyday planning the two terms are used interchangeably. The difference is in how each is measured. BMR is taken under strict laboratory conditions: a darkened room, on waking, after eight hours of sleep in the facility and a 12-hour fast, lying still. RMR is measured under more relaxed conditions — no overnight stay, no full fast — so it captures a little of the energy your body spends on digestion and minor movement.
Because of those looser conditions, a measured RMR typically lands about 10% higher than a measured BMR. That gap is real in a lab — but it does not appear in the math here. The predictive equations (Mifflin-St Jeor and friends) were built to estimate resting energy from height, weight, age, and sex, and they do not add the 10%. So a calculated RMR and a calculated BMR from the same inputs are the same number. The distinction matters when someone hands you a metabolic cart printout, not when you are using a formula.
| BMR | RMR | |
|---|---|---|
| Measured after | 8 hrs sleep + 12 hr fast | Light rest, no full fast |
| Conditions | Strict, lab-controlled | Relaxed, clinic or gym |
| Includes digestion | No | A little |
| Measured value | Baseline | ≈ 10% higher than BMR |
| Predicted (this tool) | Mifflin-St Jeor | Same Mifflin-St Jeor value |
Measured RMR exceeds measured BMR; predicted RMR equals predicted BMR.
RMR vs BMR vs TDEE
Three acronyms get tangled together. The simplest way to keep them straight is to picture them stacked: BMR is the strict floor, RMR sits just above it in real measurement, and total daily energy expenditure (TDEE) is the whole stack — everything you actually burn once movement, work, exercise, and digestion are added in. It is TDEE, not RMR, that tells you how much to eat.
To turn your RMR into daily needs, multiply by an activity factor that matches a typical day — the calculator above shows every level at once. For a deeper breakdown including a deficit or surplus, use the TDEE calculator or the calorie calculator, which build on the RMR figure shown here.
| Activity level | Multiplier | What it means |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| Lightly active | 1.375 | Light exercise 1–3 days a week |
| Moderately active | 1.55 | Moderate exercise 3–5 days a week |
| Very active | 1.725 | Hard exercise 6–7 days a week |
| Athlete | 1.9 | Twice-daily training or physical job plus exercise |
Daily needs = RMR × activity factor. These are the standard factors paired with Mifflin-St Jeor.
A worked example using the RMR calculator
Daniel is 30, stands 175 cm, and weighs 75 kg. He wants his resting calorie burn before adding any activity. Here is the arithmetic the calculator runs through the men's Mifflin-St Jeor equation.
Step 1 — Weight and height terms
10 × 75 = 750, and 6.25 × 175 = 1,093.75.
Step 2 — Age term and the male constant
5 × 30 = 150, which is subtracted, and the men's formula adds +5 at the end.
Step 3 — Add it all up
750 + 1,093.75 − 150 + 5 = 1,698.75, which rounds to about 1,699 calories a day at rest.
Now see how that compares. An RMR near 1,700 calories sits squarely in the typical range for an adult man (about 1,500–1,800). The next sections show what counts as a good RMR, what moves it, and how lab measurement differs from this estimate.
Mifflin-St Jeor vs Katch-McArdle
Mifflin-St Jeor estimates RMR from height, weight, age, and sex — population averages that work well for most people. But it cannot see your body composition, and muscle burns far more energy at rest than fat does. If you know your body-fat percentage, the Katch-McArdle equation keys entirely off your lean mass instead, which can be more accurate for very lean or very muscular bodies that the average-based formula misjudges.
Neither formula is universally "right". Use Mifflin-St Jeor when you do not know your body fat — it is the safe default and the one most calculators show. Reach for Katch-McArdle when you have a reliable body-fat reading and a body composition that sits well away from average, where the lean-mass approach earns its keep.
What is a good RMR?
There is no single "good" RMR — a higher number is not better, it simply reflects a larger or more muscular body. As rough typical ranges, adult women sit around 1,200–1,500 calories a day and adult men around 1,500–1,800, with averages near 1,400 and 1,600 respectively. A bigger body has more tissue to maintain, so it naturally posts a higher RMR.
What actually matters is using your own number as a baseline and tracking how it changes. An RMR that holds steady or rises as you build muscle is a healthy sign; one that drifts down sharply during aggressive dieting is a signal to eat more, not less. Compare yourself to your past self, not to a stranger of a different height and build.
What affects your resting metabolic rate
Two people of the same age and weight can have noticeably different resting burns. Several factors push RMR up or down:
- Muscle mass — lean muscle burns more calories at rest than fat does, so a more muscular body has a higher RMR. This is the single factor you can most change, through resistance training.
- Body size — a larger body has more tissue to maintain, so taller and heavier people generally have a higher RMR.
- Age — RMR tends to decline through adulthood, largely because muscle mass falls and body fat rises with the years.
- Sex — men usually have a higher RMR than women of the same size, reflecting their larger average share of muscle.
- Genetics — inherited differences mean some people simply run a faster or slower metabolism than others of similar build.
- Hormones and thyroid — thyroid hormones set your metabolic pace; an underactive thyroid lowers RMR and an overactive one raises it.
How to increase your RMR
You cannot rewrite your genetics, but you can nudge your resting burn upward. The levers that actually move RMR, in rough order of impact:
- Build lean muscle. Resistance training adds the most metabolically active tissue you have. Studies of strength training have measured resting-burn increases around 7–8%, and every extra kilogram of muscle adds meaningfully to your daily floor.
- Eat enough protein. Protein has the highest thermic effect of the three macronutrients — your body spends more energy digesting it — and it supports the muscle that drives RMR.
- Add high-intensity intervals. Short, hard bursts can keep your metabolism elevated for hours after the session, on top of the calories burned during it.
- Don't under-eat for long. Extended aggressive deficits prompt the body to defend itself by lowering resting burn and shedding muscle — the opposite of what you want. Build deficits from your TDEE, not from your RMR.
- Sleep well. Chronic sleep loss disrupts the hormones that govern appetite and metabolism; well-rested people tend to stay leaner on the same intake.
How to measure your RMR accurately
This calculator gives a well-grounded estimate. Because it works from population averages, any individual result can sit roughly 10% above or below the truth — it cannot see your unique body composition. To know your real number, you need it measured.
The gold standard is indirect calorimetry: you breathe into a metabolic cart (or wear a mask) while it measures the oxygen you consume and the carbon dioxide you produce, then calculates the energy that gas exchange represents. RMR tests are widely available at fitness centres, sports-medicine clinics, and some doctors' offices precisely because — unlike a strict BMR test — they do not require an overnight lab stay. For a reliable reading, you typically rest quietly for 10–20 minutes, having avoided food, caffeine, and exercise beforehand.
RMR calculator definitions
Sources and methodology
RMR is estimated with the Mifflin-St Jeor equation (Mifflin MD, St Jeor ST, et al., A new predictive equation for resting energy expenditure in healthy individuals, American Journal of Clinical Nutrition, 1990). The American Dietetic Association's 2005 review of predictive equations identified it as the most reliable for adults. The optional body-fat-based estimate uses the Katch-McArdle equation. Activity factors (1.2–1.9) are the standard multipliers applied to estimate total daily energy expenditure.
Mifflin-St Jeor equation, American Journal of Clinical Nutrition (1990); ADA review of RMR predictive equations (2005).Frequently asked questions about the free rmr calculator
About this RMR calculator
This RMR calculator runs entirely in your browser. Your height, weight, age, sex, and body fat never leave your device — nothing is sent to a server, logged, or shared. It estimates your resting metabolic rate with the Mifflin-St Jeor equation, adds an optional Katch-McArdle estimate when you enter a body-fat percentage, and multiplies by standard activity factors to show your daily calorie needs, updating instantly.
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