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TDEE Calculator

A free calculator that estimates how many calories you burn in a day, with a basic macronutrient split. On a GLP-1 it gives you a rough baseline for judging whether a much smaller intake is too low.

Updated Sep 26, 2026

The TDEE Calculator (external link) is a free website that estimates your Total Daily Energy Expenditure (TDEE): the calories your body burns in a day, counting both resting metabolism and activity. When appetite suppression has you eating much less, it gives you a rough baseline to compare your intake against.

How it works

You enter your sex, age, height and weight, pick an activity level from sedentary to athlete, and can add your body fat percentage if you know it, which can improve accuracy. The calculator first estimates your Basal Metabolic Rate (BMR, the calories you'd burn at complete rest), then multiplies it by an activity factor. It shows your estimated TDEE along with your BMR, BMI and a macronutrient breakdown (inputs and outputs as of September 2026).

The macro breakdown is a generic split of your calories into protein, carbs and fat. It isn't a personalized protein target, so work out protein separately; our guide to protein, fat, and carbohydrates covers how.

Using it on a GLP-1

Appetite suppression makes it easy to lose track of what your body needs, as opposed to what you happen to be eating. A TDEE estimate gives you a rough sense of your baseline needs, so you can tell whether a much smaller intake is in a reasonable range or too low for your goals.

Treat the number as a planning input, not a figure to hit every day:

  1. Use it as a starting point for calorie goals, then refine them with your prescriber or a dietitian. Our discussion guide on talking to a dietitian or trainer can help with that conversation.
  2. Pair it with tracking. The calculator estimates what you need, and an app like Cronometer records what you actually eat. Comparing the two shows you the gap.
  3. Recalculate as you lose weight. TDEE changes as your weight changes, so a number from the start of treatment won't stay accurate. Redoing it every so often (for example, after each 10-15 lbs lost) keeps it useful.

The estimate also works as a check against eating too little, which is easy to do when appetite is low. If you're aiming for weight loss or body recomposition, knowing your baseline tells you whether you're in a deficit, at maintenance or in a surplus. And it gives you a concrete number to bring to your care team.

Limits

TDEE calculators give an estimate, and individual metabolism varies. They also can't account for any effect of the medication itself, and the evidence on that is early. In a phase 1 trial, tirzepatide increased fat oxidation in people with obesity but didn't change metabolic adaptation, the drop in energy expenditure that normally comes with weight loss (Ravussin et al., Cell Metabolism, 2025, DOI (external link)). Start from the calculator's range and adjust based on how your weight actually responds.

Research findings above are attributed to PubMed-indexed articles with DOI links.

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