BMR vs TDEE vs maintenance calories: what's the difference?

Here's why the three terms keep colliding in search results (and in your own head), which BMR formula is actually the more accurate one, and the one habit — eating close to BMR instead of TDEE — that quietly stalls more diets than a bad macro split ever does.

The three terms, side by side

Notice BMR is always the smallest of the three. TDEE and maintenance are always the same, and usually run 20–70% above BMR depending on how active you genuinely are — a mostly-sedentary desk job sits near the low end of that range, someone training six days a week sits near the top.

"TDEE" and "maintenance calories" are the same number — so why two names?

Because they came from two different rooms. TDEE is the term researchers and dietitians use in papers and clinical notes. "Maintenance calories" is what people actually say out loud, and it's the phrase most calorie-tracking apps show on screen because it explains itself: eat this many, your weight holds. There's no separate formula for one versus the other — if you've calculated your TDEE, you already have your maintenance number. Only BMR is genuinely a different measurement.

Which BMR formula should you actually trust?

Most calculators quietly pick between two equations: Harris-Benedict, which dates to 1919 and was revised in 1984, and Mifflin-St Jeor, published in 1990. They don't always agree, and the gap matters, because BMR is the base every TDEE number is built on.

A 2005 systematic review in the Journal of the American Dietetic Association compared the major predictive equations against measured resting metabolic rate in both non-obese and obese adults, and found the Mifflin-St Jeor equation was the most accurate of the group for both.¹ That's why most current tools, including ours, default to it rather than the older Harris-Benedict formula. Neither equation reads your actual metabolism — both are population averages with a real margin of error — but Mifflin-St Jeor is the better-fitting average. (For the exact formula and a full worked calculation, see our maintenance calories guide.)

The mistake: eating close to BMR instead of TDEE

Here's where the confusion actually costs people something. Some aggressive diets — and a surprising number of default targets inside tracking apps — land uncomfortably close to BMR, on the logic that a bigger deficit means faster results. It doesn't hold up.

A 2014 review in the Journal of the International Society of Sports Nutrition on metabolic adaptation describes what happens when energy restriction runs too deep for too long: hormonal shifts (falling leptin and thyroid hormone among them) and drops in spontaneous daily movement push measured energy expenditure down further than the loss of body weight alone would predict.² In plain terms, your body doesn't sit still while you starve it near its floor — it actively pulls expenditure down and hunger up to close the gap, which is exactly the combination that makes a diet impossible to sustain.

The fix isn't complicated: take your deficit off TDEE, not off BMR, and keep it moderate. Our calorie deficit guide covers the actual range that works without triggering this.

So which number do you actually eat at?

• Losing weight: eat below your TDEE/maintenance number, by a moderate amount — never chase BMR as if it were a target.
• Holding weight: eat at your TDEE/maintenance number.
• Gaining weight: eat above it.

If you want the exact deficit size for your situation, how many calories to lose weight walks through it.

What I actually do

Bocco's default calorie target is TDEE minus a moderate deficit, calculated with Mifflin-St Jeor the moment you finish onboarding — never anywhere near BMR. I set it up that way on purpose, after reading enough of the metabolic-adaptation research above to trust it: a target you can hold for months beats one that fights your biology for two weeks and quits. From there, Bocco reads your meals from a photo and checks your day against that number automatically; if your weight trend says the estimate's off, you nudge the target directly rather than guessing at a new formula.