Resting Metabolic Rate (RMR) and Basal Metabolic Rate (BMR) are often used as if they mean exactly the same thing, and for most everyday purposes, treating them interchangeably won’t cause any real problems. But there is a genuine technical distinction worth understanding, particularly if you’re comparing figures from different sources.
The Technical Difference
BMR is measured under very strict, controlled laboratory conditions: completely at rest, lying down, fully awake but relaxed, in a thermally neutral environment, after a 12-hour fast, and typically first thing in the morning before any activity. RMR is measured under less strict conditions – still at rest, but without the same rigorous fasting and controlled-environment requirements, making it easier to measure in practice.
Why RMR Tends to Run Slightly Higher
Because RMR measurement conditions are less strictly controlled than BMR, RMR typically comes out somewhat higher – often by around 10%, though this varies – since factors like recent food intake, mild activity before measurement, and a less rigorously controlled environment tend to push the resting energy expenditure figure up slightly compared to the stricter BMR protocol.
Does This Distinction Matter for Everyday Use?
| Context | Does the BMR/RMR Distinction Matter? |
|---|---|
| Calculating a personal calorie target | Not meaningfully – either figure serves as a reasonable base for calculating TDEE |
| Clinical or research settings | Yes – precise measurement conditions matter for accurate comparison across studies |
| Comparing your own number across different tools | Worth knowing which term a tool uses, since RMR-labelled results may run slightly higher than BMR-labelled ones for the same person |
For the vast majority of people using our BMR Calculator to build a calorie or weight loss plan, this distinction is largely academic – the Mifflin–St Jeor formula used across our calculators is designed to estimate this baseline resting energy figure, and applying it consistently matters far more than which precise technical term is used to describe the underlying measurement.
Why the Terms Get Used Interchangeably
In casual and even much professional discussion, “BMR” has become something of an umbrella term covering both concepts, partly because most people (and most calculators, including formula-based ones like Mifflin–St Jeor) are estimating a resting energy figure without the strict laboratory protocol that would technically distinguish true BMR from RMR in the first place. Since formula-based calculators can’t perfectly replicate either strict laboratory condition anyway, the practical distinction between the two terms matters less than it does in a formal research context.
What Actually Matters More Than the Terminology
Rather than worrying about which precise term applies, the more useful focus is understanding what this resting energy figure represents – covered fully in our guide on what BMR is and why it matters – and using it consistently as the foundation for calculating your TDEE and, from there, your calorie target for whatever your specific goal happens to be.
Frequently Asked Questions
Should I use RMR or BMR when calculating my calorie needs?
For practical purposes, either serves as a reasonable foundation; formula-based calculators like ours provide a consistent estimate that functions effectively as either figure for the purpose of building a full TDEE and calorie target.
Why does my gym’s body composition scan show a different number to an online BMR calculator?
Different measurement methods and formulas can produce somewhat different results; a body composition scan may be measuring RMR under its own specific protocol, which can differ from a formula-based BMR estimate.
Is one of these terms more “correct” to use?
Neither is incorrect – they refer to genuinely related but technically distinct measurements, and which term is most appropriate depends on the specific measurement method being described.
Does this distinction affect which calculator I should use?
Not significantly for everyday calorie planning purposes; consistency in which calculator and formula you use over time matters considerably more than the specific RMR/BMR terminology involved.