What's the difference between BMR and TDEE?

BMR (basal metabolic rate) is the energy your body uses at complete rest — to keep your heart beating, brain running, and temperature stable. TDEE (total daily energy expenditure) is BMR multiplied by an activity factor that accounts for movement, exercise, and the small thermic effect of food. TDEE is what you actually burn in a typical day.

Are predictive calorie equations accurate?

Mifflin-St Jeor estimates BMR within about ±10% for healthy adults, which is the best of the common equations. TDEE adds another layer of estimation through activity factors, so the final number is a starting point, not a precise measurement. Track your weight weekly and adjust intake by 100–200 kcal in the appropriate direction if reality doesn't match the prediction.

Do calorie needs change with age?

Yes. BMR drops roughly 1–2% per decade after age 20 due to lean mass loss. Resistance training is the single most effective way to slow this decline.

Should I count calories every day forever?

Most people benefit from 4–8 weeks of careful tracking to learn portion sizes and the calorie content of common foods, then transition to a less rigorous approach. Long-term tracking can reinforce disordered patterns; if you have a history of disordered eating, work with a registered dietitian rather than tracking solo.

How is the activity multiplier chosen?

Sedentary (1.2): desk job, no formal exercise. Lightly active (1.375): light exercise 1–3 days a week. Moderately active (1.55): moderate exercise 3–5 days. Very active (1.725): hard exercise 6–7 days. Extra active (1.9): very physical job or training twice daily. Most people overestimate by one tier — be honest.

Is this a substitute for talking to a dietitian?

No. A calculator provides a number; a registered dietitian provides a strategy that fits your medical history, food preferences, and goals. If you have diabetes, kidney disease, an eating disorder history, or are pregnant, work with a clinician.

Calorie Calculator — Daily TDEE needs

Calorie Calculator

Daily calorie needs (TDEE) for weight loss, maintenance, or gain

Implements a published clinical formula — see citation

Maintained by TheHealthTools team. Not medical advice.

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How daily calorie needs are calculated

Your total daily energy expenditure (TDEE) is the number of calories you burn in a typical day — at rest, in motion, and digesting food. We compute it in two steps. First, basal metabolic rate (BMR) using the Mifflin-St Jeor equation, the most accurate of the common predictive formulas. Second, BMR multiplied by an activity factor between 1.2 (sedentary) and 1.9 (extra active).

For weight management, the rule of thumb is that a deficit or surplus of 500 kcal per day produces roughly 0.45 kg (1 lb) of weight change per week. The math is approximate — actual results vary with body composition, hormonal status, and adherence — but it's a defensible starting point. Track your weight weekly, average across days, and adjust intake by 100–200 kcal if reality diverges from the prediction.

When to seek a dietitian

See a registered dietitian (US) or registered nutritionist (UK) if you have diabetes, kidney or liver disease, are pregnant or breastfeeding, are an athlete with specific performance goals, or have a history of disordered eating. A calculator can give you a starting calorie target; a clinician helps you reach a health goal sustainably.

Frequently asked questions

A 500 kcal/day deficit produces roughly 0.45 kg (1 lb) of weight loss per week in most adults. Larger deficits speed weight loss but increase the risk of muscle loss and rebound. The calculator subtracts 500 kcal from your TDEE for the weight-loss target — a moderate, sustainable starting point.