RMR Calculator (Resting Metabolic Rate)

Estimate Energy — RMR Calculator

How to Use RMR Calculator (Resting Metabolic Rate)

1. Step 1: Enter age and sex

   Provide your age in years and select male or female.

2. Step 2: Pick units

   Choose Metric (cm, kg) or US (ft/in, lb) and enter height and weight.

3. Step 3: Optional: add body fat %

   If known, add body fat to see a lean‑mass estimate (Katch–McArdle).

4. Step 4: Select activity

   Pick your typical activity level to estimate daily calories (TDEE).

5. Step 5: View RMR and daily targets

   Read your RMR, per‑hour burn, TDEE, and suggested ranges.

Key Features

• Mifflin–St Jeor estimate
• Lean‑mass option (Katch–McArdle)
• Metric & US units
• TDEE by activity level
• Instant mobile results

Understanding Results

RMR Calculator Formula (Mifflin–St Jeor RMR)

This resting metabolic rate calculator (REE calculator) estimates energy at rest from your age, sex, height, and weight. We use the modern Mifflin–St Jeor equation as the default: bigger bodies and more lean mass generally mean higher RMR, while smaller bodies and older ages lower it. If you provide body fat percentage, the calculator also shows a lean‑mass method (Katch–McArdle) for comparison.

• Mifflin–St Jeor (male): RMR = 10×kg + 6.25×cm − 5×age + 5
• Mifflin–St Jeor (female): RMR = 10×kg + 6.25×cm − 5×age − 161
• Katch–McArdle (lean‑mass): RMR ≈ 370 + 21.6×LBM(kg)

For daily planning, multiply RMR by an activity factor to estimate total daily energy expenditure (TDEE). If you want a deeper dive into activity factors and daily calories, try the dedicated TDEE calculator.

Reference Ranges & Interpretation

RMR varies widely. As a loose reference, a healthy adult around 170 cm and 70 kg often falls near 1,400–1,700 kcal/day depending on sex, age, and composition. Differences of a few percent between methods are normal. Focus on trends: if your goal is maintenance, aim near your TDEE and monitor weekly averages. For weight loss, many people start with a modest deficit (for example, −300 to −500 kcal/day). For muscle gain, a small surplus (around +200 to +300 kcal/day) is common.

If you prefer BMR language or need side‑by‑side numbers, visit our BMR calculator. For translating energy into nutrition, explore the calorie calculator and macro calculator.

Assumptions & Limitations

Equations are population averages and do not capture all contexts (illness, extreme body composition, metabolic adaptation). Indirect calorimetry in a lab is more precise. Use this tool as a practical starting point, track your outcomes, and adjust gradually. This is information only, not medical advice.

Curious how BMI fits into energy planning? Read our BMI Guide for context, limitations, and better companion measures.

Complete Guide: RMR Calculator (Resting Metabolic Rate)

Use our rmr calculator to estimate your resting metabolic rate (REE) with metric or US units. See TDEE by activity and get clear, mobile‑friendly tips.

Your resting metabolic rate (RMR) is the energy your body uses at rest to keep you alive and functioning. It fuels breathing, circulation, temperature control, and constant cellular maintenance—even when you are not moving. Knowing your RMR gives you a solid baseline for planning nutrition, adjusting training, and understanding how daily activity translates into total calorie needs.

What is resting metabolic rate?

Resting metabolic rate (RMR), sometimes called resting energy expenditure (REE), is the amount of energy (calories) your body burns while at rest in a comfortable, thermoneutral environment. It is closely related to basal metabolic rate (BMR) but measured under slightly less strict conditions. In practice, most people and many research settings treat RMR and BMR as near‑interchangeable for planning.

RMR is influenced by your body size, height, body composition (especially lean mass), age, sex, and genetics. Larger bodies and higher lean mass usually mean a higher RMR. As we age, RMR tends to decline gradually. Short‑term dieting, illness, medication, and hormonal factors can also shift resting energy needs up or down.

RMR vs. BMR: what’s the difference?

The classic distinction is that BMR is measured under strict laboratory conditions after an overnight fast, with complete rest and minimal environmental stimulation. RMR allows a slightly more flexible setup, often reflecting real‑world rest more closely. Numerically, the values are usually very close. If your goal is to plan daily nutrition or monitor progress, either estimate provides a reasonable starting point.

If you specifically need a BMR estimate, try the dedicated BMR calculator. For most day‑to‑day planning, an RMR estimate from our tool plus an activity factor yields an excellent total daily energy expenditure (TDEE) starting point. You can then validate with outcomes and adjust gradually.

Which formulas does the RMR calculator use?

Our calculator estimates RMR using the Mifflin–St Jeor equation by default. This modern formula predicts resting energy from your age, sex, height, and weight. It is widely used in dietetics and aligns well with measured resting energy expenditure in healthy populations. When you add body fat percentage, the tool also shows a lean‑mass method (Katch–McArdle) for comparison.

• Mifflin–St Jeor (male): RMR = 10 × kg + 6.25 × cm − 5 × age + 5
• Mifflin–St Jeor (female): RMR = 10 × kg + 6.25 × cm − 5 × age − 161
• Katch–McArdle (lean‑mass method): RMR ≈ 370 + 21.6 × LBM(kg), where LBM = weight × (1 − body fat%)

The two estimates should land in a similar neighborhood. The lean‑mass approach can be particularly useful for people with atypical body composition—like athletes with higher muscle mass or individuals whose body fat estimates are known and reliable. If you don’t know your body fat percentage, use the Mifflin–St Jeor result and consider estimating body composition later with the body fat percentage calculator or by checking your lean body mass.

How to use the calculator

The tool is optimized for mobile. Start by choosing Metric (cm, kg) or US units (ft/in, lb), then enter your age, sex, height, and weight. Results update instantly. If you know your body fat percentage, expand the Advanced option to see a lean‑mass estimate alongside your Mifflin–St Jeor result.

To translate your RMR into realistic daily calories, pick the activity level that best describes your typical week. The calculator multiplies your RMR by a standard activity factor to estimate TDEE. If you prefer to explore TDEE in depth, try our dedicated TDEE calculator as a cross‑check.

Activity levels and daily calories (TDEE)

Your total daily energy expenditure (TDEE) is the sum of your resting needs (RMR) plus everything else: physical activity, non‑exercise movement, and digestion. We estimate TDEE by multiplying your RMR by an activity factor that reflects how much you move on an average day. Light activity might land around 1.375×, while heavy manual work or multiple training sessions can approach 1.9–2.0×.

There’s no single right answer here. The best approach is to pick the level that truly matches your lifestyle, check results against real outcomes (such as your weekly weight trend), and adjust gradually. If your weight is drifting up when you expected maintenance, reduce the intake slightly or pick a lower activity setting. If it’s drifting down too quickly, add some calories back.

Using body fat% and lean‑mass methods

When you enter body fat percentage, the calculator estimates RMR using the Katch–McArdle equation, which depends on lean body mass (LBM). This can be helpful when body composition is far from average—for example, competitive lifters or people returning from long layoffs. If you do not have a good body fat estimate, don’t worry—Mifflin–St Jeor is robust for most adults.

Not sure how to estimate body fat? Our body fat percentage calculator can give you a quick sense from circumferences, and the lean body mass calculator can help you sanity‑check results. As with all estimates, treat them as starting points and rely on trend data to steer adjustments.

Example calculations

Imagine a 30‑year‑old at 175 cm and 72 kg. Using Mifflin–St Jeor, the RMR estimate is typically around 1,600–1,700 kcal/day depending on sex. If that person is moderately active (3–5 training days per week), multiplying by 1.55 suggests a TDEE around 2,500–2,700 kcal/day. From there, a weight‑loss plan might target a modest deficit (for example, −300 to −500 kcal/day) while a lean mass–friendly recomposition plan might aim for maintenance or a small surplus during heavy training blocks.

Now consider someone with reliable body fat data: 25‑year‑old, 180 cm, 85 kg at 18% body fat. The Katch–McArdle method will base RMR on lean body mass, which may produce a slightly higher or lower estimate than Mifflin–St Jeor depending on whether muscle mass is above or below average. The comparison gives additional context—use the estimate that aligns with observed progress over several weeks.

From RMR to calorie targets

RMR tells you the energy cost of being alive at rest. TDEE translates that into a real‑world daily number. To set a target, decide whether you want maintenance, weight loss, or weight gain, then adjust from TDEE. For maintenance, aim near TDEE and track outcomes. For weight loss, consider a moderate calorie deficit (for example, −300 to −500 kcal/day). For gaining muscle, a small surplus (around +200 to +300 kcal/day) is typical for many lifters.

Our calorie calculator and maintenance calorie calculator can turn estimates into daily goals. If you prefer to plan macros instead of calories, try the macro calculator and consider protein intake ranges using the protein calculator. If you want a quick height‑adjusted reality check, the adult BMI calculator can provide additional context for goals over time.

Common mistakes to avoid

• Overestimating activity: choose the level you can sustain each week, not your best week of the year.
• Never updating: energy needs change with body mass, training volume, and schedule.
• Extreme swings: very large deficits or surpluses can undermine adherence and recovery.
• Ignoring sleep and stress: recovery impacts appetite, training, and energy burn.
• No feedback loop: track weekly weight averages and adjust gradually from TDEE.

Finally, remember that calculators produce estimates from population models. Individuals vary. Use your results as a clear starting point, then follow the data you generate over time—your weight trend, training quality, and how you feel.

References

Predictive equations are a practical middle ground between laboratory testing and guesswork. If you have a medical condition or are preparing for competition, consider speaking with a registered dietitian or sports dietitian for individualized guidance.

• Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. PubMed
• Katch VL, McArdle WD. Nutrition, Weight Control, and Exercise. 1977. Lean‑mass‑based estimation overview.
• Roza AM, Shizgal HM. The Harris–Benedict equation reevaluated: resting energy requirements and the body cell mass. PubMed

Next steps: double‑check activity‑based daily needs with the TDEE calculator, or move straight to planning with the calorie calculator and macro calculator.

Frequently Asked Questions