The quick difference
BMR, your basal metabolic rate, is the energy your body uses at complete rest. Think of a day spent lying still, awake, not digesting a meal. TDEE, your total daily energy expenditure, is everything you burn in a real day: that resting energy plus digestion plus every step, workout and chore.
So TDEE is always the bigger number. BMR is the floor and TDEE is the whole building.
How the two connect
Calculators get from one to the other with an activity factor. You estimate BMR, then multiply by a number from 1.2 for a mostly seated week to 1.9 for a very active one.
Take a 30-year-old man who weighs 75 kg and is 178 cm tall. The Mifflin-St Jeor equation puts his BMR at 1,717.5 kcal a day. Multiply by 1.2 and his TDEE is about 2,061. Multiply by 1.55 for a moderately active week and it's about 2,662. Same body, same BMR, a 600 kcal difference from activity alone.
Formula notes
TDEE = BMR x activity factor (1.2 to 1.9)
Which number to plan your eating on
TDEE. It's the estimate of what you burn, so it's the estimate of what keeps your weight steady. If you want to lose weight, you eat somewhat below your TDEE. If you want to gain, you eat above it.
BMR is a building block, not a food target. A common mistake is setting a diet at BMR, or below it, because it sounds like a safe minimum. For the man above, eating 1,717 kcal would put him about 945 kcal under his moderate-activity TDEE every day. That's an aggressive cut that most people shouldn't attempt without medical guidance.
Why both numbers are estimates
BMR from an equation is a prediction. Mifflin-St Jeor came from measuring 498 healthy adults, and it gives the average for someone with your height, weight, age and sex. Your real resting burn can be higher or lower, partly because the equation doesn't know how much muscle you carry.
TDEE stacks a second guess on top: your activity factor. That choice usually adds more uncertainty than the BMR does, because people tend to rate their week by their best workout. For a 40-year-old woman at 65 kg and 165 cm, BMR is about 1,320 kcal, and picking 1.55 instead of 1.375 moves her TDEE from about 1,815 to about 2,046.
Getting closer to your real numbers
For BMR, the reference test is indirect calorimetry, which measures the oxygen you use and the carbon dioxide you breathe out. Some clinics offer it. For most people it isn't needed.
For TDEE, your own data beats any formula. Start with an estimate, eat close to it for a few weeks, and watch your average weight. If it holds, that's your maintenance. Our BMR calculator gives you the starting point, and the TDEE calculator adds the activity layer.
If you're pregnant, breastfeeding, under 18, managing a medical condition or have a history of disordered eating, skip the self-experiment and work out your needs with a clinician or registered dietitian.
Frequently asked questions
Is BMR or TDEE higher?
TDEE is always higher, because it adds digestion and all activity to your resting energy. Even a mostly seated day adds about 20% on top of BMR with the standard 1.2 factor.
Does BMR go down with age?
In the Mifflin-St Jeor equation, yes: it subtracts 5 kcal a day for each year of age, with weight and height held the same. Ten years older means about 50 kcal less.
Can I use BMR instead of TDEE for weight loss?
It's not a good idea. Eating at BMR usually means a large deficit below your true daily burn. Start from TDEE and choose a moderate deficit instead.
How much of TDEE is BMR?
For most people, resting energy is the largest part. With activity factors of 1.2 to 1.9, BMR works out to between about half and about 83% of the estimated TDEE.
References
These sources support the method or guidance used for BMR Calculator. Verify time-sensitive rules at the source.
Try the calculator
Open BMR Calculator, enter your scenario, and compare its supporting rows with this guide's method and checks.