Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
If you have researched calories and metabolism, you have probably seen both terms: BMR and RMR. Understanding BMR vs RMR helps you choose the right number for your daily calorie planning. While they are similar, the difference matters – especially when using a BMR calculator versus a clinical measurement.
What Is BMR?
BMR stands for Basal Metabolic Rate. It measures the minimum number of calories your body needs to keep you alive at complete rest – lying down, not moving, not digesting food, in a neutral temperature room. It is the strictest definition of resting energy.
BMR is measured under very specific conditions:
- After 8 hours of sleep
- 12 hours of fasting
- Lying down in a dark, temperature‑controlled room
- No movement or muscle tension
Because of these strict conditions, true BMR is difficult to measure outside a laboratory. Most people never get a clinical BMR test. Instead, they use a BMR calculator that estimates it using formulas like Mifflin‑St Jeor.
What Is RMR?
RMR stands for Resting Metabolic Rate. It measures how many calories your body burns at rest, but under less strict conditions. You do not need to be completely fasted or lying perfectly still. Typically, RMR is measured in the morning after a light meal, while sitting or lying down.
RMR is usually slightly higher than BMR – about 10‑20% higher – because it includes the energy needed for digestion, light movement, and a more normal resting state.
For practical purposes, most people use RMR as their daily baseline because it is easier to measure and closer to real‑life conditions.
Key Differences: BMR vs RMR
| Feature | BMR | RMR |
|---|---|---|
| Measurement conditions | Very strict (fasting, dark room, no movement) | Relaxed (light meal allowed, sitting or lying) |
| Typical value | Lower (baseline) | 10‑20% higher than BMR |
| How measured | Clinical lab only | Lab or portable device |
| Best for | Medical research, critical care | Daily calorie planning, weight management |
| Commonly estimated by | Online calculators | Also online calculators (often used interchangeably) |
Which One Should You Use for Weight Loss?
For setting calorie targets, using RMR is more practical because it reflects your body in a normal resting state – not the extreme conditions of a true BMR test.
However, most online BMR vs RMR calculators (including ours) use formulas originally designed for BMR but produce numbers that actually align better with RMR. The Mifflin‑St Jeor equation, for example, was validated against measured BMR but gives results that work well as a resting baseline for daily use.
Practical advice: Do not get stuck on the terminology. Use our BMR calculator to get a number. Then treat that number as your resting baseline (which is essentially your RMR). From there, multiply by activity factors in our TDEE calculator to get your total daily burn.
Why Do Both Terms Exist?
The distinction comes from research settings. Scientists needed a strict, repeatable definition – BMR. Later, they realised that measuring BMR is impractical for most people, so they developed RMR protocols that are easier to administer and still useful.
Today, many studies and fitness professionals use the terms interchangeably. But if you want to be precise:
- BMR = what your body burns in a coma
- RMR = what your body burns while binge‑watching TV after breakfast
For almost everyone, RMR is the relevant number.
How to Estimate Your RMR at Home
You do not need a lab. Use these steps:
- Calculate your BMR using our BMR calculator.
- For a rough RMR, add 10%.
Example: BMR 1,500 → RMR ~1,650. - For a more precise RMR, use our TDEE calculator with the “sedentary” activity level – that gives you your maintenance calories with very little activity, which is close to RMR.
Alternatively, you can track your food intake and weight for two weeks while doing minimal activity. Your maintenance calories under those conditions are a good proxy for RMR.
Real Example: BMR vs RMR in Practice
Take a 35‑year‑old male, 80 kg, 175 cm.
- BMR (Mifflin‑St Jeor): (10×80) + (6.25×175) – (5×35) + 5 = 800 + 1,093.75 – 175 + 5 = 1,724 calories/day
- Estimated RMR (BMR × 1.10): ~1,896 calories/day
If he uses his BMR (1,724) as his baseline for weight loss, he might undereat. Using his RMR (~1,900) is safer and more realistic. From there, to lose weight, he would eat below his TDEE (which is RMR plus activity), not below RMR itself.
For a complete walkthrough of setting a calorie deficit, read our calories to eat to lose weight guide.
Common Misconceptions
| Myth | Truth |
|---|---|
| BMR and RMR are the same | They are similar but RMR is typically 10‑20% higher |
| You need a lab to know your RMR | No – formulas give a good estimate for most people |
| BMR is what you should eat for weight loss | No – eating at BMR is too low and slows metabolism |
| RMR changes dramatically day to day | It is fairly stable, but changes with muscle mass and body weight over time |
How to Improve Your RMR
Your resting metabolic rate is not fixed. You can raise it by:
- Building muscle – muscle burns more calories at rest than fat. Learn more in how to increase metabolism naturally.
- Eating enough protein – protein has a higher thermic effect. See how much protein per day to build muscle.
- Avoiding crash diets – prolonged very low calorie intake lowers RMR.
- Staying active – even light movement (NEAT) contributes.
For a deeper dive into the formulas that estimate BMR and RMR, check our post on BMR formula: Mifflin‑St Jeor vs. Harris‑Benedict.
Frequently Asked Questions
Is RMR higher than BMR?
Yes, typically by 10‑20%. RMR includes digestion and a more normal resting state.
Can I measure my RMR at home without equipment?
You can estimate it using our BMR calculator plus 10%. For better accuracy, use a food and weight log for two weeks while keeping activity very consistent.
Which number should I use for my maintenance calories?
Use your TDEE, which starts from your BMR/RMR and adds activity. Our maintenance calories guide explains the full process.
Does intermittent fasting affect BMR or RMR?
No, meal timing does not change your resting metabolic rate. However, very low calorie intake during fasting windows could lower it over time. Read our intermittent fasting beginner’s guide for safe practices.
If I have a low RMR, can I lose weight?
Yes – but you may need a smaller deficit and more activity. Focus on strength training to raise RMR over time. Our how many calories to eat to lose weight guide gives safe targets even for low RMR individuals.
