BMR Calculator
BMR, or Basal Metabolic Rate, is the number of calories your body needs at complete rest to keep you alive. It covers essential functions such as breathing, circulation, temperature regulation, and organ activity. That makes BMR the foundation of every calorie calculation. Once you know your BMR, you can layer in daily movement and exercise to estimate TDEE, or Total Daily Energy Expenditure. The two are related, but they are not the same. BMR is rest only. TDEE is your full day. Formula choice also matters. Mifflin-St Jeor is generally the best starting point for the general population because it tends to produce the most reliable everyday estimates. Harris-Benedict is older and often runs a bit higher. Katch-McArdle can be the best option when you know your body fat percentage, because it uses lean mass directly. Comparing all three can help you understand the likely range before setting calories.
For informational purposes only
This calculator provides estimates based on established scientific formulas. Results are not medical or nutritional advice. Individual needs vary. Consult a registered dietitian or healthcare provider before making significant dietary changes, especially if you have a medical condition.
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Frequently asked questions
What is BMR and how is it different from TDEE?
BMR is the amount of energy your body uses at complete rest to support basic life functions. TDEE includes BMR plus everything else you do during the day, such as walking, training, working, and digesting food. BMR is the base layer, while TDEE is the full daily total.
Which BMR formula is most accurate?
For most people, Mifflin-St Jeor is the strongest default choice. Harris-Benedict is a classic formula but often estimates slightly higher needs. Katch-McArdle can be the most accurate when you have a reasonably accurate body fat percentage because it accounts for lean mass.
Can I increase my BMR?
You cannot change BMR dramatically overnight, but you can influence it over time. Building more lean mass, staying physically active, recovering well, and avoiding aggressive crash dieting can all help support metabolic rate. Most day-to-day calorie burn changes come from activity and body size rather than from large swings in BMR itself.
Does BMR decrease with age?
Yes, BMR usually trends downward with age, especially if muscle mass decreases and daily activity drops. That is one reason calorie needs often change over time. Strength training and maintaining lean mass can help reduce that decline.
How do I use my BMR to lose weight?
Use BMR as the starting point, then estimate TDEE by applying an activity multiplier. Once you know TDEE, create a moderate calorie deficit rather than trying to eat at or below BMR. Weight-loss planning based only on BMR is usually too aggressive and not very sustainable.
What is the difference between BMR and RMR?
BMR is measured under stricter laboratory conditions after complete rest and fasting. RMR, or Resting Metabolic Rate, is measured under more practical conditions and is often slightly higher. In everyday use, the terms are often treated similarly, but technically they are not identical.