TDEE vs BMR vs Calorie Deficit vs Maintenance Calories: What's the Difference?

These four terms get used almost interchangeably in fitness content, which is exactly why they're confusing. They're not interchangeable — each describes a different point in the same chain of calculations, and mixing them up is one of the most common reasons people misjudge how much to eat. This page defines each one plainly, shows how they connect, and links to the calculator that answers each.

The quick comparison

How they connect

All of these terms describe stops along the same chain of arithmetic, not competing ideas. Read left to right, it looks like this:

Start with BMR — a number that assumes you never got out of bed. Multiply it by an activity factor (1.2 for sedentary, up to 1.9 for very active) to get TDEE, which is the same figure as "maintenance calories." From there, subtracting roughly 300–500 kcal creates a deficit for fat loss, or adding a similar amount creates a surplus for muscle or weight gain. Everything downstream of BMR is really just TDEE with an adjustment applied to it.

BMR: the number before any movement

Basal Metabolic Rate is what your body burns doing nothing at all — no walking, no digesting food, not even sitting up. It's almost entirely organ function: the heart pumping, lungs breathing, brain running, cells repairing. For most adults it accounts for 60–75% of total daily calories burned, which is a larger share than people expect given how little BMR actually represents in terms of activity.

BMR on its own isn't a number to eat at. It's a component used to calculate TDEE, not a target — eating at your BMR would mean eating as if you spent the entire day unconscious, which puts almost everyone into a much larger deficit than intended.

TDEE and maintenance calories: the same number, two names

Total Daily Energy Expenditure is BMR multiplied by an activity factor that accounts for movement, exercise, and the energy cost of digesting food. "Maintenance calories" is the plain-English version of the same figure — the amount that keeps your weight where it is. If you see both terms in the same article, they're describing one number, not two.

This is the number worth anchoring to. Every other calculation on this page — deficit, surplus, even macro targets — starts from TDEE rather than from BMR directly.

Calorie deficit and surplus: adjustments, not separate numbers

A deficit or surplus only makes sense relative to TDEE — there's no such thing as "a 500 calorie deficit" in isolation, only 500 calories below whatever your TDEE happens to be. Get the TDEE estimate wrong and the deficit built on top of it is wrong by the same margin, which is why it's worth calculating TDEE carefully before worrying about the size of the gap.

The size of the gap matters too. Moderate deficits (300–500 kcal) tend to outperform aggressive ones over any period longer than a few weeks, mostly because they're easier to sustain and cost less muscle mass along the way — the full reasoning is in the calorie deficit guide.

NEAT: the part of TDEE that moves the most

Non-exercise activity thermogenesis is everything you burn through movement that isn't structured exercise — pacing on a call, taking the stairs, general restlessness. It's already folded into TDEE through the activity multiplier, so it isn't a separate number to calculate. What makes it worth naming is that NEAT varies enormously between people of identical size and training habits, by several hundred calories a day in some cases, which is a major reason two people with the same calculated TDEE genuinely need different amounts of food.

Macros: a different axis entirely

Macros (protein, carbohydrate, and fat) don't sit on the same BMR-to-deficit chain at all — they answer "what should this number be made of?" rather than "what should this number be?" Total calories, set via TDEE and a deficit or surplus, determine whether you gain, lose, or maintain weight. Macros determine what a given weight change is made of and how sustainable the process feels. Get the calorie side right and the macro side wrong, and you'll likely still hit your weight goal — just probably losing more muscle, or feeling hungrier, than a good macro split would have allowed. The full breakdown is in the macro guide.

This guide is for general education purposes and isn't medical advice. Individual energy needs vary with medical conditions, medication, and other factors a formula can't see — check your plan with a doctor or registered dietitian if you're managing a health condition.