Resting Metabolic Rate (RMR) Calculator

What resting metabolic rate is

You entered a few details and got back a Resting Metabolic Rate. So what is that, and what do you do with it? This page keeps it plain, including one honest note about which formula sits behind the number.

Your Resting Metabolic Rate, or RMR, is roughly the calories your body spends over a day doing nothing active at all, just running the essentials: heartbeat, breathing, keeping your kidneys and brain going, holding your temperature steady. It is the biggest single slice of the energy most people burn in a day, and it is the sensible starting point for working out how much you need to eat.

RMR and BMR: what is the difference?

You will see RMR and BMR used almost interchangeably, and for everyday purposes they are close enough to treat as the same thing. But there is a real distinction, and it is worth thirty seconds.

Basal Metabolic Rate is the stricter of the two. A true BMR is measured in a lab under tight conditions: first thing in the morning, after a full night's rest, having fasted overnight, lying completely still in a temperature-controlled room. Resting Metabolic Rate is the same idea measured under gentler, more realistic conditions, without all the overnight requirements. Because those conditions are looser, RMR usually comes out a little higher than a true BMR, and it is the figure most gyms and clinics actually use, simply because it is far easier to measure.

The short version: BMR is the textbook floor, and RMR is the practical everyday version of the same idea, sitting just above it.

The formula this calculator uses

Here is the honest note. There is no separate, universally agreed "RMR formula", so calculators borrow one of the established resting-energy equations. This tool uses the original Harris-Benedict equation, from 1919, in its rounded form:

Men: RMR = 66 + (13.7 × weight in kg) + (5 × height in cm) − (6.8 × age in years)
Women: RMR = 655 + (9.6 × weight in kg) + (1.85 × height in cm) − (4.7 × age in years)

Weight in kilograms, height in centimetres, age in years, with pounds and metres converted for you. Worth knowing: this is the oldest of the common equations, and it tends to read a little high for modern bodies. That is not a real problem here, since RMR itself sits a little above BMR anyway, but if you want the equation considered most accurate today, our Mifflin-St Jeor Calculator uses it.

A worked example

Take a 28 year old man, 180 cm tall, 75 kg. Into the men's line:

RMR = 66 + (13.7 × 75) + (5 × 180) − (6.8 × 28)
RMR = 66 + 1027.5 + 900 − 190.4
RMR ≈ 1803 Calories/day

So his body burns in the region of 1,803 calories a day at rest. That is the base. Anything he does on top, walking, working, training, adds to it, which is how you get from this resting figure to a full daily calorie need.

What the number is good for

An RMR figure is the anchor for calorie planning. On its own it tells you the floor, the calories you would need if you did nothing all day. To get your actual daily need, you scale it up for activity, then eat around that depending on whether you want to hold, lose, or gain weight.

This tool reports the resting number by itself and leaves the activity step to you. If you would rather the calculator did that step and handed you a daily total, the TDEE Calculator and the BMR Calculator both build the activity multiplier in. Same starting idea, one step further along.

Where the estimate can be off

This is a formula estimate from population averages, so keep its limits in view:

• It cannot see your body composition. Two people of the same age, height, weight and sex get the same figure, even though the one carrying more muscle genuinely burns more at rest.
• It uses an old equation. The original 1919 Harris-Benedict tends to run high for modern, less active bodies. Newer equations fit most people better.
• Health changes it. Thyroid conditions, medications, pregnancy, breastfeeding and illness all shift real resting energy in ways this cannot capture.
• It is a starting point, not a diet. The number is one input into eating well, not an instruction on its own.

For general planning it does the job. For medical decisions, or if a condition affects your metabolism, treat it as background and check with a doctor or a registered dietitian.

Questions people ask

Is RMR the same as BMR?

Nearly, and most people use the words interchangeably. The difference is how strictly each is measured: BMR under tight lab conditions, RMR under looser ones. RMR usually lands a little higher as a result. For planning your meals, the distinction rarely matters.

Do I eat my RMR number of calories?

No. Your RMR is the resting floor. Eating only that while living a normal, active life would leave you well short. Scale it up for your activity to estimate real daily needs, then adjust for your goals.

Can I raise my RMR?

A little, and mostly through muscle. Lean tissue burns more energy at rest than fat, so building muscle nudges your resting rate up over time. The effect is modest and slow, and no supplement or food does it in any meaningful way.

References

Where the figures come from. The equation this tool runs is the original Harris-Benedict, from Harris and Benedict's 1919 Carnegie monograph. For context, the finding that newer equations such as Mifflin-St Jeor predict resting energy more accurately for most people comes from a systematic review by the Academy of Nutrition and Dietetics, and the Mifflin-St Jeor equation itself was published in 1990.

1. Harris JA, Benedict FG. A Biometric Study of Basal Metabolism in Man. Washington, DC: Carnegie Institution of Washington; 1919. Publication No. 279.
2. Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association. 2005;105(5):775-789. https://doi.org/10.1016/j.jada.2005.02.005
3. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition. 1990;51(2):241-247. https://doi.org/10.1093/ajcn/51.2.241