The number is what you burn doing nothing
RMR is the calories your body spends over 24 hours just staying alive: breathing, circulation, brain activity, keeping organs and cells running. In a fairly inactive person it is 60 to 75 percent of everything they burn in a day.
This is the Mifflin-St Jeor equation, the current standard. The older Harris-Benedict equation reads a little higher and is mostly kept for comparison.
RMR and BMR are not quite the same measurement
| RMR | BMR | |
|---|---|---|
| Conditions | Ordinary rest, roughly 30 min | Lab, fasted 8 to 12 hours |
| Typical value | Baseline | About 5 to 10% lower |
| Best used for | Everyday calorie planning | Research and clinical work |
Any equation is an average with a margin of roughly 10 to 20 percent either way. Treat the result as a starting estimate, then adjust from real weight change over two to three weeks.
From RMR to a calorie target
- Add your activity. Multiply RMR by 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (very active) or 1.9 (athlete) to get total daily burn.
- Then set the gap. Eat about 500 below that to lose near a pound a week, or 500 above to gain. Deficits past 750 tend to cost muscle and stall.
- Muscle raises the floor. Muscle burns more at rest than fat, so resistance training is the durable way to push RMR up rather than let it drift down with age.
Common questions
What is the difference between RMR and BMR?
They measure the same thing, calories burned at rest, but under different conditions. BMR is taken in a lab after overnight fasting and full rest; RMR is measured in ordinary conditions and runs about 5 to 10 percent higher. For everyday diet planning they are used interchangeably.
What makes one person burn more at rest than another?
Mostly body size and muscle. A bigger, taller, more muscular body burns more at rest than a smaller one, since muscle is more metabolically active than fat. Age lowers it slowly as muscle is lost.
How do I turn RMR into how much I should eat?
Multiply RMR by an activity factor to get total daily burn, then subtract about 500 calories to lose roughly a pound a week, or add 500 to gain. The multiplier runs from 1.2 for sedentary up to about 1.9 for very hard training.
