The difference between BMR (calories at rest) and TDEE (total daily calories burned), the Mifflin-St Jeor formula explained with a worked example, and how to use these numbers for weight loss or muscle gain.
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest, just to keep you alive — breathing, circulating blood, maintaining body temperature, and basic cell function. It does not include any movement, digestion of food, or exercise.
Think of BMR as the calorie cost of simply existing for 24 hours if you stayed in bed the entire time. It's typically the largest component of your total daily calorie burn, even for active people.
There are several formulas for estimating BMR, but Mifflin-St Jeor (1990) is widely regarded as one of the more accurate options for most healthy adults, and is the formula used in our calculator:
| Sex | Formula |
|---|---|
| Men | BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5 |
| Women | BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161 |
Get your Basal Metabolic Rate using the Mifflin-St Jeor formula.
Open BMR Calculator →TDEE (Total Daily Energy Expenditure) takes your BMR and multiplies it by an activity factor that reflects how much you move during the day:
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Little to no exercise | BMR × 1.2 |
| Lightly active | Light exercise 1-3 days/week | BMR × 1.375 |
| Moderately active | Moderate exercise 3-5 days/week | BMR × 1.55 |
| Very active | Hard exercise 6-7 days/week | BMR × 1.725 |
| Super active | Very hard training, physical job | BMR × 1.9 |
Sarah, a 30-year-old woman who weighs 65kg and is 165cm tall, moderately active:
| Step | Calculation | Result |
|---|---|---|
| BMR | (10 × 65) + (6.25 × 165) − (5 × 30) − 161 | 1,370 calories/day |
| TDEE | 1,373 × 1.55 (moderately active) | ~2,124 calories/day |
So Sarah burns roughly 1,370 calories just existing, and around 2,124 calories total on a typical moderately active day — the gap between those two numbers (about 754 calories) represents what her daily movement and exercise add on top of her baseline.
Get your full daily calorie burn including activity level — useful for any weight goal.
Open TDEE Calculator →For a precise look at how to split those calories across protein, carbs and fat, see our guide on calculating macros for your specific goal.
Basal metabolic rate is the energy your body uses at complete rest simply to stay alive — maintaining body temperature, circulating blood, breathing, repairing tissue, and running the brain. It is the floor beneath everything else.
Total daily energy expenditure adds everything on top of that floor: the energy cost of digesting food, of formal exercise, and of all the ordinary movement of a day. For most people, BMR is by some distance the largest component of TDEE, which surprises those who assume exercise dominates.
The frequently overlooked component is non-exercise activity — walking, standing, doing housework, fidgeting. It varies enormously between individuals and, in the same individual, between days. It commonly exceeds the energy cost of a gym session.
Predictive equations such as Mifflin-St Jeor were derived by measuring the metabolic rate of many people and fitting an equation to the results. The equation therefore describes the average of that population, and individuals scatter around it.
Two people matching on every input the equation accepts — age, sex, height, weight — can have measurably different actual metabolic rates. The equation cannot see body composition, and lean tissue is metabolically more active than fat tissue, which is a substantial part of the difference.
The equations also perform less reliably at the extremes of body size, and were largely developed in populations that may not represent everyone. Treating the output as your personal, precise metabolic rate overstates what the arithmetic can deliver.
Converting BMR to TDEE requires multiplying by an activity factor. Because that factor is chosen from a handful of broad descriptions, it is the single largest source of error in the whole calculation.
An accredited practising dietitian can assess your requirements in a way no equation can, particularly if you are pregnant or breastfeeding, managing a medical condition such as diabetes or thyroid disease, taking medications that affect metabolism, training at a high level, or have a history of disordered eating.
If thinking about energy intake, food, or body weight is causing distress or occupying a great deal of your attention, please talk to your GP. In Australia, the Butterfly Foundation National Helpline provides free confidential support on 1800 33 4673.
BMR estimates the energy needed to keep you alive at rest. TDEE adds digestion, movement, and exercise on top. Both are produced by equations fitted to population averages, and both carry genuine uncertainty for any individual.
The activity multiplier introduces more error than the BMR equation itself. Use the output as a reasonable starting point, observe your own trend over several weeks, adjust modestly, and pay attention to how you actually feel.
This page provides general information only and is not medical or dietetic advice. For individualised guidance, consult an accredited practising dietitian or your GP.
BMI is a ratio of weight to height. It cannot see body composition, which is why it is a population screening tool rather than an individual diagnosis.